firebird-mirror/src/jrd/dyn_mod.epp

/*
 *	PROGRAM:	JRD Data Definition Utility
 *	MODULE:		dyn_mod.epp
 *	DESCRIPTION:	Dynamic data definition - DYN_modify_<x>
 *
 * The contents of this file are subject to the Interbase Public
 * License Version 1.0 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy
 * of the License at http://www.Inprise.com/IPL.html
 *
 * Software distributed under the License is distributed on an
 * "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express
 * or implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * The Original Code was created by Inprise Corporation
 * and its predecessors. Portions created by Inprise Corporation are
 * Copyright (C) Inprise Corporation.
 *
 * All Rights Reserved.
 * Contributor(s): ______________________________________.
 * 2001.5.20: Claudio Valderrama: when changing a domain's name,
 *	if it has dimensions, rdb$field_dimensions should be updated, too.
 * 2001.5.23: Claudio Valderrama: Forbid zero length identifiers,
 *	they are not ANSI SQL compliant.
 * 2001.5.27 Claudio Valderrama: Prevent rdb$field_length from going
 *	out of sync when toggling between char and varchar data types.
 *	This caused check_update_fld_type() to lose ability to detect potentially
 *	dangerous changes. For example, you could alter a field or a domain and
 *	be able to change char(10) to varchar(8).
 *	Unfortunately, Borland chose to have DYN_modify_global_field() and add to the
 *	party DYN_modify_sql_field(); therefore bug fixes should be done twice.
 * 2001.10.08 Claudio Valderrama: put a comment with suggested code to hide
 *	special non-system triggers from user manipulation.
 * 2002-02-24 Sean Leyne - Code Cleanup of old Win 3.1 port (WINDOWS_ONLY)
 * 2002.08.10 Dmitry Yemanov: ALTER VIEW
 */

#include "firebird.h"
#include "dyn_consts.h"
#include <stdio.h>
#include <string.h>

#include "../jrd/common.h"
#include "../jrd/jrd.h"
#include "../jrd/tra.h"
#include "../jrd/scl.h"
#include "../jrd/drq.h"
#include "../jrd/flags.h"
#include "../jrd/ibase.h"
#include "../jrd/lls.h"
#include "../jrd/met.h"
#include "../jrd/btr.h"
#include "../jrd/ini.h"
#include "../jrd/intl.h"
#include "../jrd/dyn.h"
#include "../jrd/ods.h"
#include "../jrd/blb_proto.h"
#include "../jrd/cmp_proto.h"
#include "../jrd/dyn_proto.h"
#include "../jrd/dyn_df_proto.h"
#include "../jrd/dyn_md_proto.h"
#include "../jrd/dyn_ut_proto.h"
#include "../jrd/err_proto.h"
#include "../jrd/exe_proto.h"
#include "../jrd/gds_proto.h"
#include "../jrd/inf_proto.h"
#include "../jrd/intl_proto.h"
#include "../jrd/isc_f_proto.h"
#include "../jrd/met_proto.h"
#include "../jrd/vio_proto.h"
#include "../jrd/dsc_proto.h"
#include "../common/utils_proto.h"
#include "../dsql/DdlNodes.h"
#include "../dsql/metd_proto.h"
#include "../jrd/PreparedStatement.h"

using MsgFormat::SafeArg;

using namespace Jrd;
using namespace Firebird;


DATABASE DB = STATIC "ODS.RDB";

static const UCHAR alloc_info[] = { isc_info_allocation, isc_info_end };

static void change_backup_mode(Global*, UCHAR verb);
static void modify_lfield_position(thread_db*, Global*, const MetaName&, const MetaName&,
	USHORT, USHORT);
static bool check_view_dependency(thread_db*, Global*, const MetaName&, const MetaName&);
static bool check_sptrig_dependency(thread_db*, Global*,  const MetaName&, const MetaName&);
static void modify_lfield_index(thread_db*, Global*, const MetaName&, const MetaName&,
	const MetaName&);
static bool field_exists(thread_db*, Global*, const MetaName&, const MetaName&);
static bool domain_exists(thread_db*, Global*, const MetaName&);
static void get_domain_type(thread_db*, Global*, dyn_fld&);
static ULONG check_update_fld_type(const dyn_fld&, const dyn_fld&);
static ULONG check_update_numeric_type(const dyn_fld&, const dyn_fld&);
static void modify_err_punt(thread_db*, ULONG, const dyn_fld&, const dyn_fld&);


void DYN_modify_database( Global* gbl, const UCHAR** ptr)
{
/**************************************
 *
 *	D Y N _ m o d i f y _ d a t a b a s e
 *
 **************************************
 *
 * Functional description
 *	Modify a database.
 *
 **************************************/
	UCHAR s[128];

	thread_db* tdbb = JRD_get_thread_data();
	Database* dbb = tdbb->getDatabase();
	Jrd::Attachment* attachment = tdbb->getAttachment();

	jrd_req* request = NULL;

	try {

		INF_database_info(alloc_info, sizeof(alloc_info), s, sizeof(s));

		if (s[0] != isc_info_allocation) {
			goto dyn_punt_84;
		}

		request = CMP_find_request(tdbb, drq_m_database, DYN_REQUESTS);

		const SSHORT length = gds__vax_integer(s + 1, 2);
		SLONG start = gds__vax_integer(s + 3, length);

		FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
			DBB IN RDB$DATABASE

			if (!DYN_REQUEST(drq_m_database))
				DYN_REQUEST(drq_m_database) = request;

			MODIFY DBB USING
				UCHAR verb;
				while ((verb = *(*ptr)++) != isc_dyn_end)
				{
					switch (verb)
					{
					case isc_dyn_security_class:
						if (GET_STRING(ptr, DBB.RDB$SECURITY_CLASS))
							DBB.RDB$SECURITY_CLASS.NULL = FALSE;
						else
							DBB.RDB$SECURITY_CLASS.NULL = TRUE;
						break;

					case isc_dyn_def_file:
						DYN_define_file(gbl, ptr, (SLONG) 0, &start, 84);
						break;

					case isc_dyn_def_difference:
						DYN_define_difference(gbl, ptr);
						break;

					case isc_dyn_drop_difference:
					case isc_dyn_begin_backup:
					case isc_dyn_end_backup:
						change_backup_mode(gbl, verb);
						break;

					case isc_dyn_fld_character_set_name:
						if (!tdbb->getAttachment()->locksmith())
							ERR_post(Arg::Gds(isc_adm_task_denied));

						if (GET_STRING(ptr, DBB.RDB$CHARACTER_SET_NAME))
							DBB.RDB$CHARACTER_SET_NAME.NULL = FALSE;
						else
							DBB.RDB$CHARACTER_SET_NAME.NULL = TRUE;
						break;

					case isc_dyn_fld_collation:
						{
							MetaName collation;
							GET_STRING(ptr, collation);

							if (!DBB.RDB$CHARACTER_SET_NAME.NULL)
							{
								string sql;
								sql.printf("alter character set \"%s\" set default collation \"%s\"",
									PreparedStatement::escapeName(DBB.RDB$CHARACTER_SET_NAME).c_str(),
									PreparedStatement::escapeName(collation).c_str());

								AutoPtr<PreparedStatement> ps(attachment->prepareStatement(tdbb,
									gbl->gbl_transaction, sql));
								ps->execute(tdbb, gbl->gbl_transaction);
							}
						}
						break;

					default:
						--(*ptr);
						DYN_execute(gbl, ptr, NULL, NULL, NULL, NULL, NULL);
					}
				}
			END_MODIFY;
		END_FOR;

	if (!DYN_REQUEST(drq_m_database))
		DYN_REQUEST(drq_m_database) = request;

	}
	catch (const Exception& ex)
	{
		stuff_exception(tdbb->tdbb_status_vector, ex);
		DYN_rundown_request(request, -1);
		DYN_error_punt(true, 84);
		// msg 84: "MODIFY DATABASE failed"
	}

	return;

dyn_punt_84:
	DYN_error_punt(true, 84);
	// msg 84: "MODIFY DATABASE failed"
}


void DYN_modify_exception( Global* gbl, const UCHAR** ptr)
{
/**************************************
 *
 *	D Y N _ m o d i f y _ e x c e p t i o n
 *
 **************************************
 *
 * Functional description
 *	Modify an exception.
 *
 **************************************/
	thread_db* tdbb = JRD_get_thread_data();
	Database* dbb = tdbb->getDatabase();

	jrd_req* request = CMP_find_request(tdbb, drq_m_xcp, DYN_REQUESTS);
	bool found = false;

	MetaName t;
	GET_STRING(ptr, t);

	try {

		found = false;
		FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
			X IN RDB$EXCEPTIONS
				WITH X.RDB$EXCEPTION_NAME EQ t.c_str()

			if (!DYN_REQUEST(drq_m_xcp))
				DYN_REQUEST(drq_m_xcp) = request;

			found = true;

			DdlNode::executeDdlTrigger(tdbb, gbl->gbl_transaction, DdlNode::DTW_BEFORE,
				DDL_TRIGGER_ALTER_EXCEPTION, t, gbl->sqlText);

			MODIFY X
				UCHAR verb;
				while ((verb = *(*ptr)++) != isc_dyn_end)
					switch (verb)
					{
					case isc_dyn_xcp_msg:
						GET_BYTES(ptr, X.RDB$MESSAGE);
						X.RDB$MESSAGE.NULL = FALSE;
						break;

					default:
						DYN_unsupported_verb();
					}
			END_MODIFY;
		END_FOR;

		if (!DYN_REQUEST(drq_m_xcp))
			DYN_REQUEST(drq_m_xcp) = request;

	} // try
	catch (const Exception& ex)
	{
		stuff_exception(tdbb->tdbb_status_vector, ex);
		DYN_rundown_request(request, -1);
		DYN_error_punt(true, 145);
		// msg 145: "MODIFY EXCEPTION failed"
	}

	if (found)
	{
		DdlNode::executeDdlTrigger(tdbb, gbl->gbl_transaction, DdlNode::DTW_AFTER,
			DDL_TRIGGER_ALTER_EXCEPTION, t, gbl->sqlText);
	}
	else
	{
		DYN_error_punt(false, 144);
		// msg 144: "Exception not found"
	}
}


// *************************************
// D Y N _ m o d i f y _ f u n c t i o n
// *************************************
// Its purpose is to change the comment in the function's record and to
// allow changing the entry point and/or the module name.
void DYN_modify_function(Global* gbl, const UCHAR** ptr)
{
	thread_db* tdbb = JRD_get_thread_data();
	Database* dbb = tdbb->getDatabase();

	jrd_req* request = CMP_find_request(tdbb, drq_m_fun, DYN_REQUESTS);
	bool found = false;

	SqlIdentifier t;
	GET_STRING(ptr, t);

	try {
		FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
			X IN RDB$FUNCTIONS
			WITH X.RDB$FUNCTION_NAME EQ t AND
				 X.RDB$PACKAGE_NAME MISSING

			if (!DYN_REQUEST(drq_m_fun))
				DYN_REQUEST(drq_m_fun) = request;

			if (!X.RDB$ENGINE_NAME.NULL)
				status_exception::raise(Arg::Gds(isc_dyn_newfc_oldsyntax) << t);

			DdlNode::executeDdlTrigger(tdbb, gbl->gbl_transaction, DdlNode::DTW_BEFORE,
				DDL_TRIGGER_ALTER_FUNCTION, t, gbl->sqlText);

			found = true;
			MODIFY X
				UCHAR verb;
				while ((verb = *(*ptr)++) != isc_dyn_end)
				{
					switch (verb)
					{
					case isc_dyn_func_module_name:
						GET_STRING(ptr, X.RDB$MODULE_NAME);
						X.RDB$MODULE_NAME.NULL = FALSE;
						break;

					case isc_dyn_func_entry_point:
						GET_STRING(ptr, X.RDB$ENTRYPOINT);
						X.RDB$ENTRYPOINT.NULL = FALSE;
						break;

					default:
						DYN_unsupported_verb();
					}
				}
			END_MODIFY;
		END_FOR;

		if (!DYN_REQUEST(drq_m_fun))
			DYN_REQUEST(drq_m_fun) = request;
	}
	catch (const Exception& ex)
	{
		stuff_exception(tdbb->tdbb_status_vector, ex);
		DYN_rundown_request(request, -1);
		DYN_error_punt(true, 92);
		// msg 92: "MODIFY RDB$FUNCTIONS failed"
	}

	if (found)
	{
		DdlNode::executeDdlTrigger(tdbb, gbl->gbl_transaction, DdlNode::DTW_AFTER,
			DDL_TRIGGER_ALTER_FUNCTION, t, gbl->sqlText);
	}
	else
	{
		DYN_error_punt(false, 41, t);
		// msg 41: "Function %s not found"
	}
}


void DYN_modify_global_field(Global* gbl,
							 const UCHAR** ptr,
							 const MetaName* relation_name,
							 MetaName* field_name)
{
/**************************************
 *
 *	D Y N _ m o d i f y _ g l o b a l _ f i e l d
 *
 **************************************
 *
 * Functional description
 *	Execute a dynamic ddl statement.
 * Note: a global field here is a SQL domain.
 *
 **************************************/
	thread_db* tdbb = JRD_get_thread_data();
	Database* dbb = tdbb->getDatabase();

	jrd_req* request = CMP_find_request(tdbb, drq_m_gfield, DYN_REQUESTS);
	bool found = false;

	dyn_fld orig_dom, new_dom;

	try {

	bool dtype, scale, prec, subtype, charlen, collation, fldlen, nullflg, charset;
	dtype = scale = prec = subtype = charlen = collation = fldlen = nullflg = charset = false;

	bool bqryname, bqryhdr, bedtstr, bmissingval, bfldvald, bfldvaldsrc,
		bdelvald, bdeldflt, bflddftval, bflddfltsrc;
	bqryname = bqryhdr = bedtstr = bmissingval = false;
	bfldvald = bfldvaldsrc = bdelvald = bdeldflt = bflddftval = bflddfltsrc = false;

	const UCHAR *qryname, *edtstr;
	const UCHAR *qryhdr, *missingval, *fldvald, *fldvaldsrc, *flddftval, *flddfltsrc;

	GET_STRING(ptr, orig_dom.dyn_fld_name);

	int field_adjusted_count = 0;

	FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
		FLD IN RDB$FIELDS WITH FLD.RDB$FIELD_NAME EQ orig_dom.dyn_fld_name.c_str()

		if (!DYN_REQUEST(drq_m_gfield))
			DYN_REQUEST(drq_m_gfield) = request;

		found = true;

		DdlNode::executeDdlTrigger(tdbb, gbl->gbl_transaction, DdlNode::DTW_BEFORE,
			DDL_TRIGGER_ALTER_DOMAIN, orig_dom.dyn_fld_name, gbl->sqlText);

		DSC_make_descriptor(&orig_dom.dyn_dsc,
							FLD.RDB$FIELD_TYPE,
							FLD.RDB$FIELD_SCALE,
							FLD.RDB$FIELD_LENGTH,
							FLD.RDB$FIELD_SUB_TYPE,
							FLD.RDB$CHARACTER_SET_ID, FLD.RDB$COLLATION_ID);

		orig_dom.dyn_charbytelen = FLD.RDB$FIELD_LENGTH;
		orig_dom.dyn_dtype = FLD.RDB$FIELD_TYPE;
		orig_dom.dyn_precision = FLD.RDB$FIELD_PRECISION;
		orig_dom.dyn_sub_type = FLD.RDB$FIELD_SUB_TYPE;
		orig_dom.dyn_charlen = FLD.RDB$CHARACTER_LENGTH;
		orig_dom.dyn_collation = FLD.RDB$COLLATION_ID;
		orig_dom.dyn_null_flag = FLD.RDB$NULL_FLAG != 0;

		// If the original field type is an array, force its blr type to blr_blob
		bool has_dimensions = false;
		if (FLD.RDB$DIMENSIONS != 0)
		{
			orig_dom.dyn_dtype = blr_blob;
			has_dimensions = true;
		}

		bool single_validate = false;

		UCHAR verb;
		while ((verb = *(*ptr)++) != isc_dyn_end)
		{
			switch (verb)
			{
			case isc_dyn_fld_name:
				{
					MetaName newfld;

					GET_STRING(ptr, newfld);

					if (!domain_exists(tdbb, gbl, newfld))
					{
						MODIFY FLD USING
							strcpy(FLD.RDB$FIELD_NAME, newfld.c_str());
							FLD.RDB$FIELD_NAME.NULL = FALSE;
							jrd_req* old_request = request;
							request = NULL;
							// CVC: Let's update the dimensions, too.
							if (has_dimensions)
							{
								FOR (REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
									DIM_DOM IN RDB$FIELD_DIMENSIONS
									WITH DIM_DOM.RDB$FIELD_NAME EQ orig_dom.dyn_fld_name.c_str()
									MODIFY DIM_DOM USING
										strcpy (DIM_DOM.RDB$FIELD_NAME, newfld.c_str());
										DIM_DOM.RDB$FIELD_NAME.NULL = FALSE;
									END_MODIFY;
								END_FOR;
								CMP_release (tdbb, request);
								request = NULL;
							}
							// CVC: End modification.
							FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
								DOM IN RDB$RELATION_FIELDS
								WITH DOM.RDB$FIELD_SOURCE EQ orig_dom.dyn_fld_name.c_str()
								MODIFY DOM USING
									strcpy(DOM.RDB$FIELD_SOURCE, newfld.c_str());
									DOM.RDB$FIELD_SOURCE.NULL = FALSE;
								END_MODIFY;
								modify_lfield_index(tdbb, gbl,
													DOM.RDB$RELATION_NAME,
													DOM.RDB$FIELD_NAME,
													DOM.RDB$FIELD_NAME);
							END_FOR;
							CMP_release(tdbb, request);
							request = old_request;
						END_MODIFY;
					}
					else
					{
						DYN_error_punt(false, 204, SafeArg() << orig_dom.dyn_fld_name.c_str() <<
									   newfld.c_str());
						// msg 204: Cannot rename domain %s to %s.  A domain with that name already exists.
					}

					break;
				}

			case isc_dyn_rel_name:
				GET_STRING(ptr, new_dom.dyn_rel_name);
				break;

			// CVC: The syntax for DDL alter domain was accepting multiple
			// changes in one command even to the same features, IE two length alterations.
			// This repetitive type change will cause havoc so it should be stopped in the future.

			case isc_dyn_fld_length:
				fldlen = true;
				new_dom.dyn_dsc.dsc_length = DYN_get_number(ptr);
				if (++field_adjusted_count > 2)
				{
					EXE_unwind(tdbb, request);
					DYN_error_punt(false, 148, orig_dom.dyn_fld_name.c_str());
					// msg 148: "Only one data type change to the domain %s allowed at a time"
				}
				switch (new_dom.dyn_dtype)
				{

				case blr_text:
				case blr_text2:
				case blr_varying:
				case blr_varying2:
				case blr_cstring:
				case blr_cstring2:
					new_dom.dyn_charbytelen = new_dom.dyn_dsc.dsc_length;
					break;
				default:
					new_dom.dyn_charbytelen = 0; // It won't be used, anyway.
					break;
				}
				break;

			case isc_dyn_fld_type:
				dtype = true;
				new_dom.dyn_dtype = DYN_get_number(ptr);
				if (++field_adjusted_count > 2)
				{
					EXE_unwind(tdbb, request);
					DYN_error_punt(false, 148, orig_dom.dyn_fld_name.c_str());
					// msg 148: "Only one data type change to the domain %s allowed at a time"
				}

				switch (new_dom.dyn_dtype)
				{
				case blr_text:
				case blr_text2:
				case blr_varying:
				case blr_varying2:
				case blr_cstring:
				case blr_cstring2:
					if (new_dom.dyn_dsc.dsc_length && !new_dom.dyn_charbytelen)
						new_dom.dyn_charbytelen = new_dom.dyn_dsc.dsc_length;
					new_dom.dyn_dsc.dsc_length = DSC_string_length(&new_dom.dyn_dsc);
					break;
				case blr_short:
					new_dom.dyn_dsc.dsc_length = 2;
					break;

				case blr_long:
				case blr_float:
					new_dom.dyn_dsc.dsc_length = 4;
					break;

				case blr_int64:
				case blr_sql_time:
				case blr_sql_date:
				case blr_timestamp:
				case blr_double:
				case blr_d_float:
					new_dom.dyn_dsc.dsc_length = 8;
					break;

				default:
					break;
				}
				break;

			case isc_dyn_fld_scale:
				scale = true;
				new_dom.dyn_dsc.dsc_scale = DYN_get_number(ptr);
				break;

			case isc_dyn_fld_precision:
				prec = true;
				new_dom.dyn_precision = DYN_get_number(ptr);
				break;

			case isc_dyn_fld_sub_type:
				subtype = true;
				new_dom.dyn_sub_type = DYN_get_number(ptr);
				break;

			case isc_dyn_fld_char_length:
				charlen = true;
				new_dom.dyn_charlen = DYN_get_number(ptr);
				break;

			case isc_dyn_fld_collation:
				collation = true;
				new_dom.dyn_collation = DYN_get_number(ptr);
				break;

			case isc_dyn_fld_character_set:
				charset = true;
				new_dom.dyn_charset = DYN_get_number(ptr);
				break;

			case isc_dyn_fld_not_null:
				nullflg = true;
				new_dom.dyn_null_flag = true;
				break;

			case isc_dyn_fld_query_name:
				qryname = *ptr;
				bqryname = true;
				DYN_skip_attribute(ptr);
				break;

			case isc_dyn_fld_query_header:
				qryhdr = *ptr;
				bqryhdr = true;
				DYN_skip_attribute(ptr);
				break;

			case isc_dyn_fld_edit_string:
				edtstr = *ptr;
				bedtstr = true;
				DYN_skip_attribute(ptr);
				break;

			case isc_dyn_fld_missing_value:
				missingval = *ptr;
				bmissingval = true;
				DYN_skip_attribute(ptr);
				break;

			case isc_dyn_single_validation:
				if (single_validate)
				{
					EXE_unwind(tdbb, request);
					DYN_error_punt(false, 160);
					// msg 160: "Only one constraint allowed for a domain"
					break;
				}

				single_validate = true;
				break;

			case isc_dyn_fld_validation_blr:
				if (single_validate && (!FLD.RDB$VALIDATION_BLR.NULL))
				{
					EXE_unwind(tdbb, request);
					DYN_error_punt(false, 160);
					// msg 160: "Only one constraint allowed for a domain"
					break;
				}

				single_validate = true;
				fldvald = *ptr;
				bfldvald = true;
				DYN_skip_attribute(ptr);
				break;

			case isc_dyn_fld_validation_source:
				fldvaldsrc = *ptr;
				bfldvaldsrc = true;
				DYN_skip_attribute(ptr);
				break;

			case isc_dyn_del_validation:
				bdelvald = true;
				break;

			case isc_dyn_del_default:
				bdeldflt = true;
				break;

			case isc_dyn_fld_default_value:
				if (has_dimensions)
				{
					DYN_error_punt(false, 226, orig_dom.dyn_fld_name.c_str());
					// msg 226: "Default value is not allowed for array type in domain %s"
				}
				flddftval = *ptr;
				bflddftval = true;
				DYN_skip_attribute(ptr);
				break;

			case isc_dyn_fld_default_source:
				if (has_dimensions)
				{
					DYN_error_punt(false, 226, orig_dom.dyn_fld_name.c_str());
					// msg 226: "Default value is not allowed for array type in domain %s"
				}
				flddfltsrc = *ptr;
				bflddfltsrc = true;
				DYN_skip_attribute(ptr);
				break;

			case isc_dyn_fld_dimensions:
				new_dom.dyn_dtype = blr_blob;
				break;

				// These should only be defined for BLOB types and should not come through with
				// any other types.  Do nothing with them.

			case isc_dyn_fld_segment_length:
				DYN_get_number(ptr);
				break;

			default:
				--(*ptr);
				DYN_execute(gbl, ptr, relation_name, field_name, NULL, NULL, NULL);
			}
		}


		// Now that we have all of the information needed, let's check to see if the field type can be modifed.
		// Only do this, however, if we are actually modifying the datatype of the domain.

		if (dtype)
		{
			DSC_make_descriptor(&new_dom.dyn_dsc,
								new_dom.dyn_dtype,
								new_dom.dyn_dsc.dsc_scale,
								new_dom.dyn_dsc.dsc_length,
								new_dom.dyn_sub_type,
								new_dom.dyn_charset,
								new_dom.dyn_collation);

			const ULONG retval = check_update_fld_type(orig_dom, new_dom);
			if (retval != FB_SUCCESS)
				modify_err_punt(tdbb, retval, orig_dom, new_dom);

			if (!new_dom.dyn_dsc.isExact() || new_dom.dyn_dsc.dsc_scale != 0)
			{
				AutoCacheRequest request(tdbb, drq_l_ident_gens, DYN_REQUESTS);

				FOR (REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
					RFR IN RDB$RELATION_FIELDS
					WITH RFR.RDB$FIELD_SOURCE = FLD.RDB$FIELD_NAME AND
						 RFR.RDB$GENERATOR_NAME NOT MISSING
				{
					// Domain @1 must be of exact number type with zero scale because it's used in
					// an identity column.
					DYN_error_punt(false, 276, SafeArg() << orig_dom.dyn_fld_name.c_str());
				}
				END_FOR
			}
		}

		MODIFY FLD USING
			if (dtype)
			{
				FLD.RDB$FIELD_TYPE = new_dom.dyn_dtype;
				FLD.RDB$FIELD_TYPE.NULL = FALSE;

				// If the datatype was changed, update any indexes that involved the domain

				jrd_req* old_request = request;
				request = NULL;
				FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
					DOM IN RDB$RELATION_FIELDS
					WITH DOM.RDB$FIELD_SOURCE EQ orig_dom.dyn_fld_name.c_str()
					modify_lfield_index(tdbb, gbl,
										DOM.RDB$RELATION_NAME,
										DOM.RDB$FIELD_NAME,
										DOM.RDB$FIELD_NAME);
				END_FOR;

				CMP_release(tdbb, request);
				request = old_request;
			}

			if (scale)
			{
				FLD.RDB$FIELD_SCALE = new_dom.dyn_dsc.dsc_scale;
				FLD.RDB$FIELD_SCALE.NULL = FALSE;
			}

			if (prec)
			{
				FLD.RDB$FIELD_PRECISION = new_dom.dyn_precision;
				FLD.RDB$FIELD_PRECISION.NULL = FALSE;
			}

			if (subtype)
			{
				FLD.RDB$FIELD_SUB_TYPE = new_dom.dyn_sub_type;
				FLD.RDB$FIELD_SUB_TYPE.NULL = FALSE;
			}

			if (charlen)
			{
				FLD.RDB$CHARACTER_LENGTH = new_dom.dyn_charlen;
				FLD.RDB$CHARACTER_LENGTH.NULL = FALSE;
			}

			if (charset)
			{
				FLD.RDB$CHARACTER_SET_ID = new_dom.dyn_charset;
				FLD.RDB$CHARACTER_SET_ID.NULL = FALSE;
			}

			if (collation)
			{
				FLD.RDB$COLLATION_ID = new_dom.dyn_collation;
				FLD.RDB$COLLATION_ID.NULL = FALSE;
			}

			if (fldlen)
			{
				// CVC: Rescue from the wrong field_length with a helper.
				if (new_dom.dyn_dsc.dsc_dtype <= dtype_varying && new_dom.dyn_charbytelen)
					FLD.RDB$FIELD_LENGTH = new_dom.dyn_charbytelen;
				else
					FLD.RDB$FIELD_LENGTH = new_dom.dyn_dsc.dsc_length;
				FLD.RDB$FIELD_LENGTH.NULL = FALSE;
			}

			if (bqryname)
			{
				if (GET_STRING(&qryname, FLD.RDB$QUERY_NAME))
					FLD.RDB$QUERY_NAME.NULL = FALSE;
				else
					FLD.RDB$QUERY_NAME.NULL = TRUE;
			}

			if (bqryhdr)
			{
				if (DYN_put_blr_blob(gbl, &qryhdr, &FLD.RDB$QUERY_HEADER))
					FLD.RDB$QUERY_HEADER.NULL = FALSE;
				else
					FLD.RDB$QUERY_HEADER.NULL = TRUE;
			}

			if (bedtstr)
			{
				if (GET_STRING(&edtstr, FLD.RDB$EDIT_STRING))
					FLD.RDB$EDIT_STRING.NULL = FALSE;
				else
					FLD.RDB$EDIT_STRING.NULL = TRUE;
			}

			if (bmissingval)
			{
				if (DYN_put_blr_blob(gbl, &missingval, &FLD.RDB$MISSING_VALUE))
					FLD.RDB$MISSING_VALUE.NULL = FALSE;
				else
					FLD.RDB$MISSING_VALUE.NULL = TRUE;
			}

			if (bfldvald)
			{
				if (DYN_put_blr_blob(gbl, &fldvald, &FLD.RDB$VALIDATION_BLR))
					FLD.RDB$VALIDATION_BLR.NULL = FALSE;
				else
					FLD.RDB$VALIDATION_BLR.NULL = TRUE;
			}

			if (bfldvaldsrc)
			{
				if (DYN_put_text_blob(gbl, &fldvaldsrc, &FLD.RDB$VALIDATION_SOURCE))
				{
					FLD.RDB$VALIDATION_SOURCE.NULL = FALSE;
				}
				else
					FLD.RDB$VALIDATION_SOURCE.NULL = TRUE;
			}

			if (bdelvald)
			{
				FLD.RDB$VALIDATION_BLR.NULL = TRUE;
				FLD.RDB$VALIDATION_SOURCE.NULL = TRUE;
			}

			if (bdeldflt)
			{
				FLD.RDB$DEFAULT_VALUE.NULL = TRUE;
				FLD.RDB$DEFAULT_SOURCE.NULL = TRUE;
			}

			if (bflddftval)
			{
				if (DYN_put_blr_blob(gbl, &flddftval, &FLD.RDB$DEFAULT_VALUE))
					FLD.RDB$DEFAULT_VALUE.NULL = FALSE;
				else
					FLD.RDB$DEFAULT_VALUE.NULL = TRUE;
			}

			if (bflddfltsrc)
			{
				if (DYN_put_text_blob(gbl, &flddfltsrc, &FLD.RDB$DEFAULT_SOURCE))
					FLD.RDB$DEFAULT_SOURCE.NULL = FALSE;
				else
					FLD.RDB$DEFAULT_SOURCE.NULL = TRUE;
			}

		END_MODIFY;
	END_FOR;

	if (!DYN_REQUEST(drq_m_gfield))
		DYN_REQUEST(drq_m_gfield) = request;

	} // try
	catch (const Exception& ex)
	{
		stuff_exception(tdbb->tdbb_status_vector, ex);
		DYN_rundown_request(request, -1);
		DYN_error_punt(true, 87);
		// msg 87: "MODIFY RDB$FIELDS failed"
	}

	if (found)
	{
		DdlNode::executeDdlTrigger(tdbb, gbl->gbl_transaction, DdlNode::DTW_AFTER,
			DDL_TRIGGER_ALTER_DOMAIN, orig_dom.dyn_fld_name, gbl->sqlText);
	}
	else
	{
		DYN_error_punt(false, 89);
		// msg 89: "Global field not found"
	}
}


void DYN_modify_index( Global* gbl, const UCHAR** ptr)
{
/**************************************
 *
 *	D Y N _ m o d i f y _ i n d e x
 *
 **************************************
 *
 * Functional description
 *	Modify an existing index
 *
 **************************************/
	MetaName name;

	thread_db* tdbb = JRD_get_thread_data();
	Database* dbb = tdbb->getDatabase();

	jrd_req* request = CMP_find_request(tdbb, drq_m_index, DYN_REQUESTS);
	bool found = false;

	try {

		GET_STRING(ptr, name);

		FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
			IDX IN RDB$INDICES WITH IDX.RDB$INDEX_NAME EQ name.c_str()

			if (!DYN_REQUEST(drq_m_index))
				DYN_REQUEST(drq_m_index) = request;

			found = true;

			DdlNode::executeDdlTrigger(tdbb, gbl->gbl_transaction, DdlNode::DTW_BEFORE,
				DDL_TRIGGER_ALTER_INDEX, name, gbl->sqlText);

			MODIFY IDX USING
				UCHAR verb;
				while ((verb = *(*ptr)++) != isc_dyn_end)
				{
					switch (verb)
					{
					case isc_dyn_idx_unique:
						IDX.RDB$UNIQUE_FLAG = DYN_get_number(ptr);
						IDX.RDB$UNIQUE_FLAG.NULL = FALSE;
						break;

					case isc_dyn_idx_inactive:
						IDX.RDB$INDEX_INACTIVE = DYN_get_number(ptr);
						IDX.RDB$INDEX_INACTIVE.NULL = FALSE;
						break;

					// For V4 index selectivity can be set only to -1
					case isc_dyn_idx_statistic:
						IDX.RDB$STATISTICS = -1.0;
						IDX.RDB$STATISTICS.NULL = FALSE;
						break;

					default:
						DYN_unsupported_verb();
					}
				}
			END_MODIFY;
		END_FOR;

		if (!DYN_REQUEST(drq_m_index))
			DYN_REQUEST(drq_m_index) = request;

	} // try
	catch (const Exception& ex)
	{
		stuff_exception(tdbb->tdbb_status_vector, ex);
		DYN_rundown_request(request, -1);
		DYN_error_punt(true, 91);
		// msg 91: "MODIFY RDB$INDICES failed"
	}

	if (found)
	{
		DdlNode::executeDdlTrigger(tdbb, gbl->gbl_transaction, DdlNode::DTW_AFTER,
			DDL_TRIGGER_ALTER_INDEX, name, gbl->sqlText);
	}
	else
	{
		DYN_error_punt(false, 48);
		// msg 48: "Index not found"
	}
}


void DYN_modify_local_field(Global* gbl, const UCHAR** ptr, const MetaName* relation_name)
{
/**************************************
 *
 *	D Y N _ m o d i f y _ l o c a l _ f i e l d
 *
 **************************************
 *
 * Functional description
 *	Execute a dynamic ddl statement.
 *
 **************************************/
	USHORT position;
	MetaName f, r;
	const UCHAR* query_name;
	const UCHAR* edit_string;
	const UCHAR* security_class;
	const UCHAR* new_name;
	const UCHAR* query_header;
	const UCHAR* new_source = NULL;

	thread_db* tdbb = JRD_get_thread_data();
	Database* dbb = tdbb->getDatabase();

	GET_STRING(ptr, f);

	bool sfflag, qnflag, qhflag, esflag, system_flag, scflag, nnflag, ntflag, npflag;
	sfflag = qnflag = qhflag = esflag = scflag = npflag = nnflag = ntflag = false;
	TriState nullFlag;

	UCHAR verb;
	while ((verb = *(*ptr)++) != isc_dyn_end)
	{
		switch (verb)
		{
		case isc_dyn_rel_name:
			GET_STRING(ptr, r);
			break;

		case isc_dyn_system_flag:
			system_flag = DYN_get_number(ptr);
			sfflag = true;
			break;

		case isc_dyn_fld_position:
			position = DYN_get_number(ptr);
			npflag = true;
			break;

		case isc_dyn_new_fld_name:
			new_name = *ptr;
			nnflag = true;
			DYN_skip_attribute(ptr);
			break;

		case isc_dyn_fld_query_name:
			query_name = *ptr;
			qnflag = true;
			DYN_skip_attribute(ptr);
			break;

		case isc_dyn_fld_query_header:
			query_header = *ptr;
			qhflag = true;
			DYN_skip_attribute(ptr);
			break;

		case isc_dyn_fld_edit_string:
			edit_string = *ptr;
			esflag = true;
			DYN_skip_attribute(ptr);
			break;

		case isc_dyn_security_class:
			security_class = *ptr;
			scflag = true;
			DYN_skip_attribute(ptr);
			break;

		case isc_dyn_fld_source:
			new_source = *ptr;
			DYN_skip_attribute(ptr);
			break;

		case isc_dyn_fld_not_null:
			nullFlag = true;
			break;

		case isc_dyn_fld_null:
			nullFlag = false;
			break;

		default:
			--(*ptr);
			DYN_execute(gbl, ptr, relation_name, NULL, NULL, NULL, NULL);
		}
	}

	jrd_req* request = CMP_find_request(tdbb, drq_m_lfield, DYN_REQUESTS);
	bool found = false;

	try {

	USHORT existing_position;
	found = false;
	FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
		FLD IN RDB$RELATION_FIELDS
			WITH FLD.RDB$FIELD_NAME EQ f.c_str()
			 AND FLD.RDB$RELATION_NAME EQ r.c_str()

		if (!DYN_REQUEST(drq_m_lfield))
			DYN_REQUEST(drq_m_lfield) = request;

		found = true;

		MODIFY FLD USING
			if (npflag)
				existing_position = FLD.RDB$FIELD_POSITION;

			if (sfflag)
			{
				FLD.RDB$SYSTEM_FLAG = system_flag;
				FLD.RDB$SYSTEM_FLAG.NULL = FALSE;
			}
			if (qnflag)
			{
				if (GET_STRING(&query_name, FLD.RDB$QUERY_NAME))
					FLD.RDB$QUERY_NAME.NULL = FALSE;
				else
					FLD.RDB$QUERY_NAME.NULL = TRUE;
			}

			if (nnflag)
			{
				MetaName new_fld;
				GET_STRING(&new_name, new_fld);

				check_view_dependency(tdbb, gbl, r, f);
				check_sptrig_dependency(tdbb, gbl, r, f);
				if (!field_exists(tdbb, gbl, r, new_fld))
				{
					strcpy(FLD.RDB$FIELD_NAME, new_fld.c_str());
					modify_lfield_index(tdbb, gbl, r, f, FLD.RDB$FIELD_NAME);
				}
				else
				{
					DYN_error_punt(false, 205, SafeArg() << f.c_str() << new_fld.c_str() <<
									r.c_str());
					// msg 205: Cannot rename field %s to %s.  A field with that name already exists in table %s.
				}
			}

			if (qhflag)
			{
				if (DYN_put_blr_blob(gbl, &query_header, &FLD.RDB$QUERY_HEADER))
					FLD.RDB$QUERY_HEADER.NULL = FALSE;
				else
					FLD.RDB$QUERY_HEADER.NULL = TRUE;
			}
			if (esflag)
			{
				if (GET_STRING(&edit_string, FLD.RDB$EDIT_STRING))
					FLD.RDB$EDIT_STRING.NULL = FALSE;
				else
					FLD.RDB$EDIT_STRING.NULL = TRUE;
			}
			if (scflag)
			{
				if (GET_STRING(&security_class, FLD.RDB$SECURITY_CLASS))
					FLD.RDB$SECURITY_CLASS.NULL = FALSE;
				else
					FLD.RDB$SECURITY_CLASS.NULL = TRUE;
			}

			if (new_source)
				GET_STRING(&new_source, FLD.RDB$FIELD_SOURCE);

			if (nullFlag.isAssigned())
			{
				if (!nullFlag.asBool() && !FLD.RDB$GENERATOR_NAME.NULL)
				{
					// msg 274: Identity column @1 of table @2 cannot be changed to NULLable
					DYN_error_punt(false, 274, SafeArg() << f.c_str() << r.c_str());
				}

				FLD.RDB$NULL_FLAG = (SSHORT) nullFlag.asBool();
			}
		END_MODIFY;
	END_FOR;

	if (!DYN_REQUEST(drq_m_lfield))
		DYN_REQUEST(drq_m_lfield) = request;

	if (npflag && found && position != existing_position)
		modify_lfield_position(tdbb, gbl, r, f, position, existing_position);
	} // try
	catch (const Exception& ex)
	{
		stuff_exception(tdbb->tdbb_status_vector, ex);
		DYN_rundown_request(request, -1);
		DYN_error_punt(true, 95);
		// msg 95: "MODIFY RDB$RELATION_FIELDS failed"
	}

	if (!found)
	{
		DYN_error_punt(false, 176, SafeArg() << f.c_str() << r.c_str());
		// msg 176: "column %s does not exist in table/view %s"
	}
}


void DYN_modify_relation( Global* gbl, const UCHAR** ptr)
{
/**************************************
 *
 *	D Y N _ m o d i f y _ r e l a t i o n
 *
 **************************************
 *
 * Functional description
 *	Modify an existing relation
 *
 **************************************/
	MetaName name, field_name;

	thread_db* tdbb = JRD_get_thread_data();
	Database* dbb = tdbb->getDatabase();

	GET_STRING(ptr, name);

	jrd_req* request = CMP_find_request(tdbb, drq_m_relation, DYN_REQUESTS);
	bool found = false;

	try {

	FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
		REL IN RDB$RELATIONS WITH REL.RDB$RELATION_NAME EQ name.c_str()

		if (!DYN_REQUEST(drq_m_relation))
			DYN_REQUEST(drq_m_relation) = request;

		if (!REL.RDB$VIEW_BLR.NULL)
			DYN_error_punt(false, 177);

		DdlNode::executeDdlTrigger(tdbb, gbl->gbl_transaction, DdlNode::DTW_BEFORE,
			DDL_TRIGGER_ALTER_TABLE, name, gbl->sqlText);

		found = true;
		MODIFY REL USING
			UCHAR verb;
			while ((verb = *(*ptr)++) != isc_dyn_end)
				switch (verb)
				{
				case isc_dyn_system_flag:
					REL.RDB$SYSTEM_FLAG = DYN_get_number(ptr);
					REL.RDB$SYSTEM_FLAG.NULL = FALSE;
					break;

				case isc_dyn_security_class:
					if (GET_STRING(ptr, REL.RDB$SECURITY_CLASS))
						REL.RDB$SECURITY_CLASS.NULL = FALSE;
					else
						REL.RDB$SECURITY_CLASS.NULL = TRUE;
					break;

				case isc_dyn_rel_ext_file:
					if (REL.RDB$EXTERNAL_FILE.NULL)
					{
						DYN_rundown_request(request, -1);
						DYN_error_punt(false, 97);
						// msg 97: "add EXTERNAL FILE not allowed"
					}
					if (!GET_STRING(ptr, REL.RDB$EXTERNAL_FILE))
					{
						DYN_rundown_request(request, -1);
						DYN_error_punt(false, 98);
						// msg 98: "drop EXTERNAL FILE not allowed"
					}
					break;

				default:
					--(*ptr);
					DYN_execute(gbl, ptr, &name, &field_name, NULL, NULL, NULL);
				}
		END_MODIFY;
	END_FOR;

	if (!DYN_REQUEST(drq_m_relation))
		DYN_REQUEST(drq_m_relation) = request;

	} // try
	catch (const Exception& ex)
	{
		stuff_exception(tdbb->tdbb_status_vector, ex);
		DYN_rundown_request(request, -1);
		DYN_error_punt(true, 99);
		// msg 99: "MODIFY RDB$RELATIONS failed"
	}

	if (found)
	{
		DdlNode::executeDdlTrigger(tdbb, gbl->gbl_transaction, DdlNode::DTW_AFTER,
			DDL_TRIGGER_ALTER_TABLE, name, gbl->sqlText);
	}
	else
	{
		DYN_error_punt(false, 101);
		// msg 101: "Relation field not found"
	}
}


void DYN_modify_view( Global* gbl, const UCHAR** ptr)
{
/**************************************
 *
 *	D Y N _ m o d i f y _ v i e w
 *
 **************************************
 *
 * Functional description
 *	Execute a dynamic ddl statement.
 *
 **************************************/
	thread_db* tdbb = JRD_get_thread_data();
	Database* dbb = tdbb->getDatabase();

	MetaName view_name;
	GET_STRING(ptr, view_name);

	jrd_req* request = NULL;
	bool found = false;

	try {

	request = CMP_find_request(tdbb, drq_m_view, DYN_REQUESTS);

	FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
		REL IN RDB$RELATIONS
			WITH REL.RDB$RELATION_NAME EQ view_name.c_str()
				AND REL.RDB$VIEW_BLR NOT MISSING

		if (!DYN_REQUEST(drq_m_view))
			DYN_REQUEST(drq_m_view) = request;

		found = true;

		DdlNode::executeDdlTrigger(tdbb, gbl->gbl_transaction, DdlNode::DTW_BEFORE,
			DDL_TRIGGER_ALTER_VIEW, view_name, gbl->sqlText);

		MODIFY REL
			REL.RDB$SYSTEM_FLAG = 0;
			REL.RDB$SYSTEM_FLAG.NULL = FALSE;
			REL.RDB$VIEW_BLR.NULL = TRUE;
			REL.RDB$VIEW_SOURCE.NULL = TRUE;

			jrd_req* request2 = NULL;

			FOR (REQUEST_HANDLE request2 TRANSACTION_HANDLE gbl->gbl_transaction)
				VR IN RDB$VIEW_RELATIONS
				WITH VR.RDB$VIEW_NAME EQ view_name.c_str()

				ERASE VR;
			END_FOR;

			CMP_release(tdbb, request2);

			request2 = NULL;

			FOR (REQUEST_HANDLE request2 TRANSACTION_HANDLE gbl->gbl_transaction)
				TRG IN RDB$TRIGGERS
				WITH TRG.RDB$RELATION_NAME EQ view_name.c_str() AND
					 TRG.RDB$SYSTEM_FLAG EQ fb_sysflag_view_check

				ERASE TRG;
			END_FOR

			CMP_release(tdbb, request2);

			UCHAR verb;
			while ((verb = *(*ptr)++) != isc_dyn_end)
			{
				switch (verb)
				{
				case isc_dyn_system_flag:
					REL.RDB$SYSTEM_FLAG = DYN_get_number(ptr);
					REL.RDB$SYSTEM_FLAG.NULL = FALSE;
					break;

				case isc_dyn_view_blr:
					if (DYN_put_blr_blob(gbl, ptr, &REL.RDB$VIEW_BLR))
						REL.RDB$VIEW_BLR.NULL = FALSE;
					else
						REL.RDB$VIEW_BLR.NULL = TRUE;
					break;

				case isc_dyn_view_source:
					if (DYN_put_text_blob(gbl, ptr, &REL.RDB$VIEW_SOURCE))
						REL.RDB$VIEW_SOURCE.NULL = FALSE;
					else
						REL.RDB$VIEW_SOURCE.NULL = TRUE;
					break;

				case isc_dyn_security_class:
					GET_STRING(ptr, REL.RDB$SECURITY_CLASS);
					REL.RDB$SECURITY_CLASS.NULL = FALSE;
					break;

				default:
					--(*ptr);
					MetaTmp(REL.RDB$RELATION_NAME)
						DYN_execute(gbl, ptr, &tmp, NULL, NULL, NULL, NULL);
				}
			}
		END_MODIFY;
	END_FOR;

	if (!DYN_REQUEST(drq_m_view))
		DYN_REQUEST(drq_m_view) = request;

	} // try
	catch (const Exception& ex)
	{
		stuff_exception(tdbb->tdbb_status_vector, ex);
		DYN_rundown_request(request, -1);
		DYN_error_punt(true, 99);
		// msg 99: "MODIFY RDB$RELATIONS failed"
	}

	if (found)
	{
		DdlNode::executeDdlTrigger(tdbb, gbl->gbl_transaction, DdlNode::DTW_AFTER,
			DDL_TRIGGER_ALTER_VIEW, view_name, gbl->sqlText);
	}
	else
	{
		DYN_error_punt(false, 54, view_name.c_str());
		// msg 54: "View %s not found"
	}
}


static void change_backup_mode( Global* gbl, UCHAR verb)
{
/**************************************
 *
 *	c h a n g e _ b a c k u p _ m o d e
 *
 **************************************
 *
 * Functional description
 *	Drop backup difference file for the database,
 *  begin or end backup
 *
 **************************************/
	bool invalid_state = false;

	thread_db* tdbb = JRD_get_thread_data();
	Database* dbb = tdbb->getDatabase();

	if (!tdbb->getAttachment()->locksmith())
	{
		ERR_post(Arg::Gds(isc_adm_task_denied));
	}

	jrd_req* request = CMP_find_request(tdbb, drq_d_difference, DYN_REQUESTS);
	bool found = false;

	try {

		FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
			X IN RDB$FILES

			if (X.RDB$FILE_FLAGS & FILE_difference)
			{
				found = true;
				switch (verb)
				{
				case isc_dyn_drop_difference:
					ERASE X;
					break;
				case isc_dyn_begin_backup:
					if (X.RDB$FILE_FLAGS & FILE_backing_up) {
						invalid_state = true;
					}
					else
					{
						MODIFY X USING
							X.RDB$FILE_FLAGS |= FILE_backing_up;
						END_MODIFY;
					}
					break;
				case isc_dyn_end_backup:
					if (X.RDB$FILE_FLAGS & FILE_backing_up)
					{
						if (X.RDB$FILE_NAME.NULL) {
							ERASE X;
						}
						else
						{
							MODIFY X USING
								X.RDB$FILE_FLAGS &= ~FILE_backing_up;
							END_MODIFY;
						}
					}
					else {
						invalid_state = true;
					}
					break;
				}
			}

		END_FOR;

		if (!DYN_REQUEST(drq_d_difference))
			DYN_REQUEST(drq_d_difference) = request;
	}
	catch (const Exception& ex)
	{
		stuff_exception(tdbb->tdbb_status_vector, ex);
		DYN_rundown_request(request, drq_d_difference);
		DYN_error_punt(true, 63);
		// msg 63: ERASE RDB$FILE failed
	}

	if (!found && verb == isc_dyn_begin_backup)
	{
		try {
			request = CMP_find_request(tdbb, drq_s2_difference, DYN_REQUESTS);
			STORE(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
				X IN RDB$FILES
				X.RDB$FILE_NAME.NULL = TRUE;
				X.RDB$FILE_FLAGS.NULL = FALSE;
				X.RDB$FILE_FLAGS = FILE_difference | FILE_backing_up;
				X.RDB$FILE_START = 0;
				X.RDB$FILE_START.NULL = FALSE;
				X.RDB$FILE_LENGTH.NULL = TRUE;
				X.RDB$SHADOW_NUMBER.NULL = TRUE;
			END_STORE;

			found = true;

			if (!DYN_REQUEST(drq_s2_difference))
			{
				DYN_REQUEST(drq_s2_difference) = request;
			}
		}
		catch (const Exception& ex)
		{
			stuff_exception(tdbb->tdbb_status_vector, ex);
			DYN_rundown_request(request, drq_s2_difference);
			DYN_error_punt(true, 150);
			// msg 150: STORE RDB$FILES failed
		}
	}

	if (invalid_state)
	{
		DYN_error_punt(false, verb == isc_dyn_begin_backup ? 217 : 218);
		// msg 217: "Database is already in the physical backup mode"
		// msg 218: "Database is not in the physical backup mode"
	}

	if (!found)
	{
		DYN_error_punt(false, verb == isc_dyn_end_backup ? 218 : 215);
		// msg 218: "Database is not in the physical backup mode"
		// msg 215: "Difference file is not defined"
	}
}


static void modify_lfield_position(thread_db* tdbb,
								   Global* gbl,
								   const MetaName& relation_name,
								   const MetaName& field_name,
								   USHORT new_position,
								   USHORT existing_position)
{
/***********************************************************
 *
 *  m o d i f y _ l f i e l d _ p o s i t i o n
 ***********************************************************
 *
 *  Functional Description:
 *     Alters the position of a field with respect to the
 *     other fields in the relation.  This will only affect
 *     the order in which the fields will be returned when either
 *     viewing the relation or performing select * from the relation.
 *
 *     The rules of engagement are as follows:
 *          if new_position > original position
 *             increase RDB$FIELD_POSITION for all fields with RDB$FIELD_POSITION
 *             between the new_position and existing position of the field
 *	       then update the position of the field being altered.
 *              just update the position
 *
 *          if new_position < original position
 *             decrease RDB$FIELD_POSITION for all fields with RDB$FIELD_POSITION
 *             between the new_position and existing position of the field
 *	       then update the position of the field being altered.
 *
 *	    if new_position == original_position -- no_op
 *
 ***********************************************************/
	jrd_req* request = NULL;

	try {

	// Find the position of the last field in the relation
	SLONG max_position = -1;
	DYN_UTIL_generate_field_position(tdbb, gbl, relation_name, &max_position);

	// If the existing position of the field is less than the new position of
	// the field, subtract 1 to move the fields to their new positions otherwise,
	// increase the value in RDB$FIELD_POSITION by one

	bool move_down = false;
	if (existing_position < new_position)
		move_down = true;

	// Retrieve the records for the fields which have a position between the
	// existing field position and the new field position

	FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
		FLD IN RDB$RELATION_FIELDS
		WITH FLD.RDB$RELATION_NAME EQ relation_name.c_str() AND
		FLD.RDB$FIELD_POSITION >= MIN(new_position, existing_position) AND
		FLD.RDB$FIELD_POSITION <= MAX(new_position, existing_position)
		MODIFY FLD USING
			// If the field is the one we want, change the position, otherwise
			// increase the value of RDB$FIELD_POSITION
			if (field_name == FLD.RDB$FIELD_NAME)
			{
				if (new_position > max_position)
				{
					// This prevents gaps in the position sequence of the fields
					FLD.RDB$FIELD_POSITION = max_position;
				}
				else
					FLD.RDB$FIELD_POSITION = new_position;
			}
			else
			{
				if (move_down)
					FLD.RDB$FIELD_POSITION = FLD.RDB$FIELD_POSITION - 1;
				else
					FLD.RDB$FIELD_POSITION = FLD.RDB$FIELD_POSITION + 1;
			}

			FLD.RDB$FIELD_POSITION.NULL = FALSE;
		END_MODIFY;
	END_FOR;

	CMP_release(tdbb, request);
	request = NULL;

	// Once the field position has been changed, make sure that there are no
	// duplicate field positions and no gaps in the position sequence (this can
	// not be guaranteed by the query above

	USHORT new_pos = 0;
	FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
		FLD IN RDB$RELATION_FIELDS WITH FLD.RDB$RELATION_NAME EQ relation_name.c_str()
			SORTED BY ASCENDING FLD.RDB$FIELD_POSITION

		if (FLD.RDB$FIELD_POSITION != new_pos)
		{
			MODIFY FLD USING
				FLD.RDB$FIELD_POSITION = new_pos;
			END_MODIFY;
		}
		new_pos += 1;
	END_FOR;

	CMP_release(tdbb, request);
	}
	catch (const Exception& ex)
	{
		stuff_exception(tdbb->tdbb_status_vector, ex);
		DYN_error_punt(true, 95);
		// msg 95: "MODIFY RDB$RELATION_FIELDS failed"
	}
}


static bool check_view_dependency(thread_db* tdbb,
									 Global* gbl,
									 const MetaName& relation_name,
									 const MetaName& field_name)
{
/***********************************************************
 *
 *  c h e c k _ v i e w _ d e p e n d e n c y
 ***********************************************************
 *
 *  Functional Description:
 *	Checks to see if the given field is referenced in a view. If the field
 *	is referenced in a view, return true, else return false
 *  CVC: The function never has a chance to return true because it punts.
 *
 ***********************************************************/
	jrd_req* request = NULL;
	bool retval = false;
	MetaName view_name;

	FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
		FIRST 1
			X IN RDB$RELATION_FIELDS CROSS Y IN RDB$RELATION_FIELDS CROSS
			Z IN RDB$VIEW_RELATIONS WITH
			X.RDB$RELATION_NAME EQ relation_name.c_str() AND
			X.RDB$FIELD_NAME EQ field_name.c_str() AND
			X.RDB$FIELD_NAME EQ Y.RDB$BASE_FIELD AND
			X.RDB$FIELD_SOURCE EQ Y.RDB$FIELD_SOURCE AND
			Y.RDB$RELATION_NAME EQ Z.RDB$VIEW_NAME AND
			X.RDB$RELATION_NAME EQ Z.RDB$RELATION_NAME AND
			Y.RDB$VIEW_CONTEXT EQ Z.RDB$VIEW_CONTEXT
		retval = true;
		view_name = Z.RDB$VIEW_NAME;
	END_FOR;

	CMP_release(tdbb, request);

	if (retval)
	{
		DYN_error_punt(false, 206, SafeArg() << field_name.c_str() <<
						relation_name.c_str() << view_name.c_str());
		// msg 206: Column %s from table %s is referenced in  %s.
	}

	return retval;
}


static bool check_sptrig_dependency(thread_db* tdbb,
									   Global* gbl,
									   const MetaName& relation_name,
									   const MetaName& field_name)
{
/***********************************************************
 *
 *  c h e c k _ s p t r i g _ d e p e n d e n c y
 ***********************************************************
 *
 *  Functional Description:
 *	Checks to see if the given field is referenced in a stored procedure
 *	or trigger.  If the field is referenced, return true, else return
 *  false, but true causes the function to punt instead.
 ***********************************************************/
	jrd_req* request = NULL;
	bool retval = false;
	MetaName dep_name;

	FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
		FIRST 1
			DEP IN RDB$DEPENDENCIES WITH
			DEP.RDB$DEPENDED_ON_NAME EQ relation_name.c_str() AND
			DEP.RDB$FIELD_NAME EQ field_name.c_str()
		retval = true;
		dep_name = DEP.RDB$DEPENDENT_NAME;
	END_FOR;

	CMP_release(tdbb, request);

	if (retval)
	{
		DYN_error_punt(false, 206, SafeArg() << field_name.c_str() <<
						relation_name.c_str() << dep_name.c_str());
		// msg 206: Column %s from table %s is referenced in %s.
	}

	return retval;
}


static void modify_lfield_index(thread_db* tdbb,
								Global* gbl,
								const MetaName&	relation_name,
								const MetaName&	field_name,
								const MetaName&	new_fld_name)
{
/***********************************************************
 *
 *  m o d i f y _ l f i e l d _ i n d e x
 ***********************************************************
 *
 *  Functional Description:
 *	Updates the field names in an index and forces the index to be rebuilt
 *	with the new field names
 *
 ***********************************************************/
	jrd_req* request = NULL;

	FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
		IDX IN RDB$INDICES CROSS IDXS IN RDB$INDEX_SEGMENTS WITH
			IDX.RDB$INDEX_NAME EQ IDXS.RDB$INDEX_NAME AND
			IDX.RDB$RELATION_NAME EQ relation_name.c_str() AND
			IDXS.RDB$FIELD_NAME EQ field_name.c_str()
		// Change the name of the field in the index
		MODIFY IDXS USING
			memcpy(IDXS.RDB$FIELD_NAME, new_fld_name.c_str(), sizeof(IDXS.RDB$FIELD_NAME));
		END_MODIFY;

		// Set the index name to itself to tell the index to rebuild
		MODIFY IDX USING
			// This is to fool both gpre and gcc.
			char* p = IDX.RDB$INDEX_NAME;
			p[MAX_SQL_IDENTIFIER_LEN] = 0;
		END_MODIFY;
	END_FOR;

	CMP_release(tdbb, request);
}


static bool field_exists(thread_db* tdbb,
						 Global* gbl,
						 const MetaName& relation_name,
						 const MetaName& field_name)
{
/***********************************************************
 *
 *  f i e l d _ e x i s t s
 ***********************************************************
 *
 *  Functional Description:
 *	Checks to see if the given field already exists in a relation
 ***********************************************************/
	jrd_req* request = NULL;
	bool retval = false;

	FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
		FLD IN RDB$RELATION_FIELDS WITH
			FLD.RDB$RELATION_NAME EQ relation_name.c_str() AND
			FLD.RDB$FIELD_NAME EQ field_name.c_str()
		retval = true;
	END_FOR;

	CMP_release(tdbb, request);
	return retval;
}


static bool domain_exists(thread_db* tdbb, Global* gbl, const MetaName& field_name)
{
/***********************************************************
 *
 *  d o m a i n _ e x i s t s
 ***********************************************************
 *
 *  Functional Description:
 *	Checks to see if the given field already exists in a relation
 ***********************************************************/
	jrd_req* request = NULL;
	bool retval = false;

	FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
		FLD IN RDB$FIELDS WITH FLD.RDB$FIELD_NAME EQ field_name.c_str()
		retval = true;
	END_FOR;

	CMP_release(tdbb, request);
	return retval;
}


void DYN_modify_sql_field(Global* gbl, const UCHAR** ptr, const MetaName* relation_name)
{
/**************************************
 *
 *	D Y N _ m o d i f y _ s q l _ f i e l d
 *
 **************************************
 *
 * Functional description
 *	Execute a dynamic ddl statement
 *      to modify the datatype of a field.
 *
 *  If there are dependencies on the field, abort the operation
 *  unless the dependency is an index.  In this case, rebuild the
 *  index once the operation has completed.
 *
 *  If the original datatype of the field was a domain:
 *     if the new type is a domain, just make the change to the new domain
 *     if it exists
 *
 *     if the new type is a base type, just make the change
 *
 *  If the original datatype of the field was a base type:
 *     if the new type is a base type, just make the change
 *
 *     if the new type is a domain, make the change to the field
 *     definition and remove the entry for RDB$FIELD_SOURCE from the original
 *     field.  In other words ... clean up after ourselves
 *
 *  The following conversions are not allowed:
 *        Blob to anything
 *        Array to anything
 *        Date to anything
 *        Char to any numeric
 *        Varchar to any numeric
 *        Anything to Blob
 *        Anything to Array
 *
 *  The following operations return a warning
 *        Decreasing the length of a char (varchar) field
 *
 *	CVC: This is a misleading comment. There's no code that
 *	produces a warning. This condition raises an error, too.
 *
 **************************************/
	thread_db* tdbb = JRD_get_thread_data();

	dyn_fld orig_fld, new_fld, dom_fld;

	try {

	GET_STRING(ptr, orig_fld.dyn_fld_name);

	// Check to see if the field being altered is involved in any type of dependency.
	// If there is a dependency, call DYN_error_punt (inside the function).
	fb_assert(relation_name);

	// ASF: check disabled to allow change of field type to be used
	// with TYPE OF COLUMN table.column feature.
	//check_sptrig_dependency(tdbb, gbl, *relation_name,
	//						orig_fld.dyn_fld_name);

	jrd_req* request = NULL;
	jrd_req* first_request = NULL;
	bool found = false;
	bool dtype, scale, prec, subtype, charlen, collation, fldlen, nullflg, charset;
	dtype = scale = prec = subtype = charlen = collation = fldlen = nullflg = charset = false;

	int field_adjusted_count = 0;

	FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
		RFR IN RDB$RELATION_FIELDS CROSS
		REL IN RDB$RELATIONS WITH
			REL.RDB$RELATION_NAME = RFR.RDB$RELATION_NAME AND
			RFR.RDB$RELATION_NAME = relation_name->c_str() AND
			RFR.RDB$FIELD_NAME = orig_fld.dyn_fld_name.c_str()
		first_request = request;
		request = NULL;

		found = true;
		bool is_view = !REL.RDB$VIEW_BLR.NULL;
		bool has_dimensions = false;
		bool update_domain = false;
		bool domain_has_default = false;
		bool domain_is_computed = false;
		SSHORT fld_position = 0;
		bool fld_position_change = false;
		SSHORT view_context = 0;
		bool view_context_change = false;
		MetaName fld_base_field;
		bool fld_base_field_change = false;
		bool orig_computed = false;

		FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
			FLD IN RDB$FIELDS WITH FLD.RDB$FIELD_NAME = RFR.RDB$FIELD_SOURCE
			// Get information about the original field type.  If a conversion
			// can not be at any time made between the two datatypes, error.
			DSC_make_descriptor(&orig_fld.dyn_dsc,
								FLD.RDB$FIELD_TYPE,
								FLD.RDB$FIELD_SCALE,
								FLD.RDB$FIELD_LENGTH,
								FLD.RDB$FIELD_SUB_TYPE,
								FLD.RDB$CHARACTER_SET_ID,
								FLD.RDB$COLLATION_ID);

			orig_fld.dyn_charbytelen = FLD.RDB$FIELD_LENGTH;
			orig_fld.dyn_dtype = FLD.RDB$FIELD_TYPE;
			orig_fld.dyn_precision = FLD.RDB$FIELD_PRECISION;
			orig_fld.dyn_sub_type = FLD.RDB$FIELD_SUB_TYPE;
			orig_fld.dyn_charlen = FLD.RDB$CHARACTER_LENGTH;
			orig_fld.dyn_collation = FLD.RDB$COLLATION_ID;
			orig_fld.dyn_null_flag = FLD.RDB$NULL_FLAG != 0;
			orig_fld.dyn_fld_source = RFR.RDB$FIELD_SOURCE;
			orig_computed = !FLD.RDB$COMPUTED_BLR.NULL;

			// If the original field type is an array, force its blr type to blr_blob
			if (FLD.RDB$DIMENSIONS != 0)
			{
				orig_fld.dyn_dtype = blr_blob;
				has_dimensions = true;
			}

			domain_has_default = !FLD.RDB$DEFAULT_VALUE.NULL;
			domain_is_computed = !FLD.RDB$COMPUTED_BLR.NULL;

			UCHAR verb;
			while ((verb = *(*ptr)++) != isc_dyn_end)
			{
				switch (verb)
				{
				case isc_dyn_fld_source:
					GET_STRING(ptr, dom_fld.dyn_fld_source);
					if (fb_utils::implicit_domain(dom_fld.dyn_fld_source.c_str()))
					{
						DYN_error_punt(false, 224, SafeArg() << dom_fld.dyn_fld_source.c_str() <<
										orig_fld.dyn_fld_name.c_str());
						// msg 224: "Cannot use the internal domain %s as new type for field %s".
					}
					get_domain_type(tdbb, gbl, dom_fld);
					update_domain = true;
					break;

				case isc_dyn_rel_name:
					GET_STRING(ptr, new_fld.dyn_rel_name);
					break;

				case isc_dyn_fld_length:
					fldlen = true;
					new_fld.dyn_dsc.dsc_length = DYN_get_number(ptr);
					if (++field_adjusted_count > 2)
					{
						DYN_error_punt(false, 149, orig_fld.dyn_fld_name.c_str());
						// msg 149: "Only one data type change to the field %s allowed at a time"
					}

					switch (new_fld.dyn_dtype)
					{
					case blr_text:
					case blr_text2:
					case blr_varying:
					case blr_varying2:
					case blr_cstring:
					case blr_cstring2:
						new_fld.dyn_charbytelen = new_fld.dyn_dsc.dsc_length;
						break;
					default:
						new_fld.dyn_charbytelen = 0; // It won't be used, anyway.
						break;
					}
					break;

				case isc_dyn_fld_type:
					dtype = true;
					new_fld.dyn_dtype = DYN_get_number(ptr);
					if (++field_adjusted_count > 2)
					{
						DYN_error_punt(false, 149, orig_fld.dyn_fld_name.c_str());
						// msg 149: "Only one data type change to the field %s allowed at a time"
					}

					switch (new_fld.dyn_dtype)
					{
					case blr_text:
					case blr_text2:
					case blr_varying:
					case blr_varying2:
					case blr_cstring:
					case blr_cstring2:
						if (new_fld.dyn_dsc.dsc_length && !new_fld.dyn_charbytelen)
							new_fld.dyn_charbytelen = new_fld.dyn_dsc.dsc_length;
						new_fld.dyn_dsc.dsc_length = DSC_string_length (&new_fld.dyn_dsc);
						break;

					case blr_short:
						new_fld.dyn_dsc.dsc_length = 2;
						break;

					case blr_long:
					case blr_float:
						new_fld.dyn_dsc.dsc_length = 4;
						break;

					case blr_int64:
					case blr_sql_time:
					case blr_sql_date:
					case blr_timestamp:
					case blr_double:
					case blr_d_float:
						new_fld.dyn_dsc.dsc_length = 8;
						break;

					default:
						break;
					}
					break;

				case isc_dyn_fld_scale:
					scale = true;
					new_fld.dyn_dsc.dsc_scale = DYN_get_number(ptr);
					break;

				case isc_dyn_fld_precision:
					prec = true;
					new_fld.dyn_precision = DYN_get_number(ptr);
					break;

				case isc_dyn_fld_sub_type:
					subtype = true;
					new_fld.dyn_sub_type = DYN_get_number(ptr);
					break;

				case isc_dyn_fld_char_length:
					charlen = true;
					new_fld.dyn_charlen = DYN_get_number(ptr);
					break;

				case isc_dyn_fld_collation:
					collation = true;
					new_fld.dyn_collation = DYN_get_number(ptr);
					break;

				case isc_dyn_fld_character_set:
					charset = true;
					new_fld.dyn_charset = DYN_get_number(ptr);
					break;

				case isc_dyn_fld_not_null:
					nullflg = true;
					new_fld.dyn_null_flag = true;
					break;

				case isc_dyn_fld_dimensions:
					new_fld.dyn_dtype = blr_blob;
					break;

				case isc_dyn_fld_position:
					fld_position = DYN_get_number(ptr);
					fld_position_change = true;
					break;

				case isc_dyn_fld_base_fld:
					GET_STRING(ptr, fld_base_field);
					fld_base_field_change = true;
					break;

				case isc_dyn_view_context:
					view_context = DYN_get_number(ptr);
					view_context_change = true;
					break;

				case isc_dyn_fld_computed_blr:
					domain_is_computed = true;
					new_fld.dyn_computed_val = *ptr;
					DYN_skip_attribute(ptr);
					break;

				case isc_dyn_fld_computed_source:
					new_fld.dyn_computed_src = *ptr;
					DYN_skip_attribute(ptr);
					break;

				case isc_dyn_del_computed:
					domain_is_computed = false;
					new_fld.dyn_drop_computed = true;
					break;

				case isc_dyn_del_default:
					new_fld.dyn_drop_default = true;
					break;

				case isc_dyn_fld_default_value:
					if (!RFR.RDB$GENERATOR_NAME.NULL)
					{
						// msg 275: Identity column @1 of table @2 cannot have default value
						DYN_error_punt(false, 275,
							SafeArg() << orig_fld.dyn_fld_name.c_str() << relation_name->c_str());
					}

					if (has_dimensions)
					{
						DYN_error_punt(false, 225, orig_fld.dyn_fld_name.c_str());
						// msg 225: "Default value is not allowed for array type in field %s"
					}
					new_fld.dyn_default_val = *ptr;
					DYN_skip_attribute(ptr);
					break;

				case isc_dyn_fld_default_source:
					if (has_dimensions)
					{
						DYN_error_punt(false, 225, orig_fld.dyn_fld_name.c_str());
						// msg 225: "Default value is not allowed for array type in field %s"
					}
					new_fld.dyn_default_src = *ptr;
					DYN_skip_attribute(ptr);
					break;

				// These should only be defined for BLOB types and should not come through with
				// any other types.  BLOB types are detected above
				case isc_dyn_fld_segment_length:
					DYN_get_number(ptr);
					break;

				default:
					--(*ptr);
					MetaTmp(RFR.RDB$FIELD_SOURCE)
						DYN_execute(gbl, ptr, relation_name, &tmp, NULL, NULL, NULL);
				}
			}

			if (fld_base_field_change && view_context_change)
			{
				fb_assert(is_view);

				if (fld_base_field.hasData())
				{
					char field_name[MAX_SQL_IDENTIFIER_SIZE];
					DYN_UTIL_find_field_source(tdbb, gbl, RFR.RDB$RELATION_NAME, view_context,
						fld_base_field.c_str(), field_name);
					dom_fld.dyn_fld_source = field_name;
					update_domain = true;
				}
				else
					DYN_UTIL_generate_field_name(tdbb, gbl, new_fld.dyn_fld_source);
			}
		END_FOR; // FLD in RDB$FIELDS
		CMP_release(tdbb, request);
		request = NULL;

		if (!is_view &&
			((new_fld.dyn_computed_val && !orig_computed) ||
				(!new_fld.dyn_computed_val && orig_computed)))
		{
			// Cannot add or remove COMPUTED from column @1
			DYN_error_punt(false, 249, SafeArg() << orig_fld.dyn_fld_name.c_str());
		}

		const bool sourceIsInternalDomain =
			fb_utils::implicit_domain(orig_fld.dyn_fld_source.c_str()) && RFR.RDB$BASE_FIELD.NULL;
		const bool changeComputed = new_fld.dyn_computed_val || new_fld.dyn_drop_computed;

		// Now that we have all of the information needed, let's check to see
		// if the field type can be modified

		if (update_domain)
		{
			// a1. Internal domain -> domain.
			// a2. Domain -> domain.

			/* CVC: Since get_domain_type() called above already called DSC_make_descriptor,
					there's no point in calling it again, since it will increment AGAIN the length
					of varchar fields! This bug detected thanks to new check field dyn_charbytelen.
			DSC_make_descriptor(&dom_fld.dyn_dsc,
								dom_fld.dyn_dtype,
								dom_fld.dyn_dsc.dsc_scale,
								dom_fld.dyn_dsc.dsc_length,
								dom_fld.dyn_sub_type,
								dom_fld.dyn_charset, dom_fld.dyn_collation);
			*/

			if (!domain_is_computed && !is_view)
			{
				if (!RFR.RDB$GENERATOR_NAME.NULL)
				{
					if (!dom_fld.dyn_dsc.isExact() || dom_fld.dyn_dsc.dsc_scale != 0)
					{
						// Identity column @1 of table @2 must be exact numeric with zero scale.
						DYN_error_punt(false, 273,
							SafeArg() << orig_fld.dyn_fld_name.c_str() << relation_name->c_str());
					}
				}

				const ULONG retval = check_update_fld_type(orig_fld, dom_fld);
				if (retval != FB_SUCCESS)
					modify_err_punt(tdbb, retval, orig_fld, dom_fld);
			}

			// If the original definition was a base field type, remove the entries from RDB$FIELDS
			if (sourceIsInternalDomain)
			{
				// a1. Internal domain -> domain.
				FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
					FLD IN RDB$FIELDS
					WITH FLD.RDB$FIELD_NAME = RFR.RDB$FIELD_SOURCE

					ERASE FLD;
				END_FOR;

				CMP_release(tdbb, request);
				request = NULL;
			}
			request = first_request;
			MODIFY RFR USING
				strcpy(RFR.RDB$FIELD_SOURCE, dom_fld.dyn_fld_source.c_str());
				RFR.RDB$FIELD_SOURCE.NULL = FALSE;
				if (domain_is_computed)
				{
					RFR.RDB$UPDATE_FLAG.NULL = FALSE;
					RFR.RDB$UPDATE_FLAG = 1;
				}

				RFR.RDB$COLLATION_ID.NULL = TRUE;	// CORE-2426
			END_MODIFY;
			first_request = request;
			request = NULL;

			FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
				PRM IN RDB$PROCEDURE_PARAMETERS
				WITH PRM.RDB$RELATION_NAME = relation_name->c_str() AND
					 PRM.RDB$FIELD_NAME = orig_fld.dyn_fld_name.c_str()

				MODIFY PRM USING
					strcpy(PRM.RDB$FIELD_SOURCE, dom_fld.dyn_fld_source.c_str());
				END_MODIFY;
			END_FOR;

			CMP_release(tdbb, request);
			request = NULL;
		}
		else
		{
			// b1. Domain -> internal domain.
			// b2. Internal domain -> internal domain.

			const UCHAR* defVal = new_fld.dyn_default_val;
			const UCHAR* defSrc = new_fld.dyn_default_src;
			const bool dropDefault = new_fld.dyn_drop_default;
			const bool changeDefault = defVal || defSrc || dropDefault;

			// If we are altering only the default, we need the old field settings.
			if (changeDefault && !new_fld.dyn_dsc.dsc_dtype)
			{
				new_fld = orig_fld;
				// We already called DSC_make_descriptor on orig_fld, so fix new_fld.
				switch (new_fld.dyn_dtype)
				{
				case blr_text:
				case blr_varying:
				case blr_cstring:
				    new_fld.dyn_dsc.dsc_length = DSC_string_length(&orig_fld.dyn_dsc);
					break;
				}
			}

			DSC_make_descriptor(&new_fld.dyn_dsc,
								new_fld.dyn_dtype,
								new_fld.dyn_dsc.dsc_scale,
								new_fld.dyn_dsc.dsc_length,
								new_fld.dyn_sub_type,
								new_fld.dyn_charset, new_fld.dyn_collation);

			if (!changeComputed && !orig_computed && !is_view)
			{
				const ULONG retval = check_update_fld_type(orig_fld, new_fld);
				if (retval != FB_SUCCESS)
					modify_err_punt(tdbb, retval, orig_fld, new_fld);

				if (!RFR.RDB$GENERATOR_NAME.NULL)
				{
					if (!new_fld.dyn_dsc.isExact() || new_fld.dyn_dsc.dsc_scale != 0)
					{
						// Identity column @1 of table @2 must be exact numeric with zero scale.
						DYN_error_punt(false, 273,
							SafeArg() << orig_fld.dyn_fld_name.c_str() << relation_name->c_str());
					}
				}
			}

			// Check to see if the original data type for the field was based on a domain.  If it
			// was (and now it isn't), remove the domain information and replace it with a generated
			// field name for RDB$FIELDS

			if (!changeDefault && !sourceIsInternalDomain)
			{
				// b1. Domain -> internal domain. Not for changing DEFAULT value.

				request = first_request;
				MODIFY RFR USING
					DYN_UTIL_generate_field_name(tdbb, gbl, RFR.RDB$FIELD_SOURCE);
					new_fld.dyn_fld_source = RFR.RDB$FIELD_SOURCE;
				END_MODIFY;
				first_request = request;
				request = NULL;

				STORE(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
					FLD IN RDB$FIELDS
					FLD.RDB$SYSTEM_FLAG = 0;
					FLD.RDB$SYSTEM_FLAG.NULL = FALSE;
					FLD.RDB$FIELD_SCALE.NULL = TRUE;
					FLD.RDB$FIELD_PRECISION.NULL = TRUE;
					FLD.RDB$FIELD_SUB_TYPE.NULL = TRUE;
					FLD.RDB$SEGMENT_LENGTH.NULL = TRUE;
					FLD.RDB$COMPUTED_BLR.NULL = TRUE;
					FLD.RDB$COMPUTED_SOURCE.NULL = TRUE;
					FLD.RDB$DEFAULT_VALUE.NULL = TRUE;
					FLD.RDB$DEFAULT_SOURCE.NULL = TRUE;
					FLD.RDB$VALIDATION_BLR.NULL = TRUE;
					FLD.RDB$VALIDATION_SOURCE.NULL = TRUE;
					FLD.RDB$NULL_FLAG.NULL = TRUE;
					FLD.RDB$EDIT_STRING.NULL = TRUE;
					FLD.RDB$DIMENSIONS.NULL = TRUE;
					FLD.RDB$CHARACTER_LENGTH.NULL = TRUE;
					FLD.RDB$CHARACTER_SET_ID.NULL = TRUE;
					FLD.RDB$COLLATION_ID.NULL = TRUE;

					if (dtype)
					{
						FLD.RDB$FIELD_TYPE = new_fld.dyn_dtype;
						FLD.RDB$FIELD_TYPE.NULL = FALSE;
					}

					if (scale)
					{
						FLD.RDB$FIELD_SCALE = new_fld.dyn_dsc.dsc_scale;
						FLD.RDB$FIELD_SCALE.NULL = FALSE;
					}

					if (prec)
					{
						FLD.RDB$FIELD_PRECISION = new_fld.dyn_precision;
						FLD.RDB$FIELD_PRECISION.NULL = FALSE;
					}

					if (subtype)
					{
						FLD.RDB$FIELD_SUB_TYPE = new_fld.dyn_sub_type;
						FLD.RDB$FIELD_SUB_TYPE.NULL = FALSE;
					}

					if (charlen)
					{
						FLD.RDB$CHARACTER_LENGTH = new_fld.dyn_charlen;
						FLD.RDB$CHARACTER_LENGTH.NULL = FALSE;
					}

					if (charset)
					{
						FLD.RDB$CHARACTER_SET_ID = new_fld.dyn_charset;
						FLD.RDB$CHARACTER_SET_ID.NULL = FALSE;
					}

					if (collation)
					{
						FLD.RDB$COLLATION_ID = new_fld.dyn_collation;
						FLD.RDB$COLLATION_ID.NULL = FALSE;
					}

					if (fldlen)
					{
						// CVC: Rescue from the wrong field_length with a helper.
						if (new_fld.dyn_dsc.dsc_dtype <= dtype_varying && new_fld.dyn_charbytelen)
							FLD.RDB$FIELD_LENGTH = new_fld.dyn_charbytelen;
						else
							FLD.RDB$FIELD_LENGTH = new_fld.dyn_dsc.dsc_length;
						FLD.RDB$FIELD_LENGTH.NULL = FALSE;
					}

					if (new_fld.dyn_computed_val)
					{
						DYN_put_blr_blob(gbl, &new_fld.dyn_computed_val, &FLD.RDB$COMPUTED_BLR);
						FLD.RDB$COMPUTED_BLR.NULL = FALSE;
					}

					if (new_fld.dyn_computed_src)
					{
						DYN_put_text_blob(gbl, &new_fld.dyn_computed_src, &FLD.RDB$COMPUTED_SOURCE);
						FLD.RDB$COMPUTED_SOURCE.NULL = FALSE;
					}

					// Copy the field name into RDB$FIELDS
					strcpy(FLD.RDB$FIELD_NAME, new_fld.dyn_fld_source.c_str());
				END_STORE;

				CMP_release(tdbb, request);
				request = NULL;

				FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
					PRM IN RDB$PROCEDURE_PARAMETERS
					WITH PRM.RDB$RELATION_NAME = relation_name->c_str() AND
						 PRM.RDB$FIELD_NAME = orig_fld.dyn_fld_name.c_str()

					MODIFY PRM USING
						strcpy(PRM.RDB$FIELD_SOURCE, new_fld.dyn_fld_source.c_str());
					END_MODIFY;
				END_FOR;

				CMP_release(tdbb, request);
				request = NULL;
			}
			else if (changeDefault)
			{
				request = first_request;
				MODIFY RFR USING
					if (dropDefault)
					{
						if (RFR.RDB$DEFAULT_VALUE.NULL)
						{
							if (sourceIsInternalDomain || !domain_has_default)
							{
								DYN_error_punt(false, 229, orig_fld.dyn_fld_name.c_str());
								// msg 229: "Local column %s doesn't have a default"
							}
							else if (domain_has_default)
							{
								DYN_error_punt(false, 230, SafeArg() << orig_fld.dyn_fld_name.c_str() <<
												orig_fld.dyn_fld_source.c_str());
								// msg 230: "Local column %s default belongs to domain %s"
							}
						}
						else
						{
							RFR.RDB$DEFAULT_VALUE.NULL = TRUE;
							RFR.RDB$DEFAULT_SOURCE.NULL = TRUE;
						}
					}
					else
					{
						if (domain_is_computed)
						{
							DYN_error_punt(false, 233, orig_fld.dyn_fld_name.c_str());
							// msg 233: "Local column %s is computed, cannot set a default value"
						}
						if (defVal)
						{
							const UCHAR* p = defVal;
							if (DYN_put_blr_blob(gbl, &p, &RFR.RDB$DEFAULT_VALUE))
								RFR.RDB$DEFAULT_VALUE.NULL = FALSE;
						}

						if (defSrc)
						{
							const UCHAR* p = defSrc;
							if (DYN_put_text_blob(gbl, &p, &RFR.RDB$DEFAULT_SOURCE))
								RFR.RDB$DEFAULT_SOURCE.NULL = FALSE;
						}
					}
				END_MODIFY
				first_request = request;
				request = NULL;
			}
			else //if (sourceIsInternalDomain)
			{
				// The original and new definitions are both base types.
				// b2. Internal domain -> internal domain.
				// Modify in place, since there cannot be other fields using it.

				//if (!sourceIsInternalDomain)
				//	DYN_UTIL_copy_domain(tdbb, gbl, orig_fld.dyn_fld_source, new_fld.dyn_fld_source);

				FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
					FLD IN RDB$FIELDS WITH FLD.RDB$FIELD_NAME = RFR.RDB$FIELD_SOURCE
					MODIFY FLD USING

						if (dtype)
						{
							FLD.RDB$FIELD_TYPE = new_fld.dyn_dtype;
							FLD.RDB$FIELD_TYPE.NULL = FALSE;
						}

						if (scale)
						{
							FLD.RDB$FIELD_SCALE = new_fld.dyn_dsc.dsc_scale;
							FLD.RDB$FIELD_SCALE.NULL = FALSE;
						}

						if (prec)
						{
							FLD.RDB$FIELD_PRECISION = new_fld.dyn_precision;
							FLD.RDB$FIELD_PRECISION.NULL = FALSE;
						}

						if (subtype)
						{
							FLD.RDB$FIELD_SUB_TYPE = new_fld.dyn_sub_type;
							FLD.RDB$FIELD_SUB_TYPE.NULL = FALSE;
						}

						if (charlen)
						{
							FLD.RDB$CHARACTER_LENGTH = new_fld.dyn_charlen;
							FLD.RDB$CHARACTER_LENGTH.NULL = FALSE;
						}

						if (charset)
						{
							FLD.RDB$CHARACTER_SET_ID = new_fld.dyn_charset;
							FLD.RDB$CHARACTER_SET_ID.NULL = FALSE;
						}

						if (collation)
						{
							FLD.RDB$COLLATION_ID = new_fld.dyn_collation;
							FLD.RDB$COLLATION_ID.NULL = FALSE;
						}

						if (fldlen)
						{
							// CVC: Rescue from the wrong field_length with a helper.
							if (new_fld.dyn_dsc.dsc_dtype <= dtype_varying && new_fld.dyn_charbytelen)
								FLD.RDB$FIELD_LENGTH = new_fld.dyn_charbytelen;
							else
								FLD.RDB$FIELD_LENGTH = new_fld.dyn_dsc.dsc_length;
							FLD.RDB$FIELD_LENGTH.NULL = FALSE;
						}

						if (changeComputed)
						{
							FLD.RDB$DEFAULT_SOURCE.NULL = TRUE;
							FLD.RDB$DEFAULT_VALUE.NULL = TRUE;

							if (new_fld.dyn_computed_val)
							{
								DYN_put_blr_blob(gbl, &new_fld.dyn_computed_val, &FLD.RDB$COMPUTED_BLR);
								FLD.RDB$COMPUTED_BLR.NULL = FALSE;
							}

							if (new_fld.dyn_computed_src)
							{
								DYN_put_text_blob(gbl, &new_fld.dyn_computed_src, &FLD.RDB$COMPUTED_SOURCE);
								FLD.RDB$COMPUTED_SOURCE.NULL = FALSE;
							}
						}

					END_MODIFY;
				END_FOR; // FLD in RDB$FIELDS
				CMP_release(tdbb, request);
				if (domain_is_computed)
				{
					request = first_request;
					MODIFY RFR USING
						RFR.RDB$UPDATE_FLAG.NULL = FALSE;
						RFR.RDB$UPDATE_FLAG = 1;
					END_MODIFY;
					first_request = request;
				}

				request = NULL;
			}
		} // else not a domain

		request = first_request;

		if (fld_position_change || view_context_change || fld_base_field_change)
		{
			MODIFY RFR USING
				if (fld_position_change)
					RFR.RDB$FIELD_POSITION = fld_position;
				if (view_context_change)
					RFR.RDB$VIEW_CONTEXT = view_context;
				if (fld_base_field_change)
				{
					RFR.RDB$BASE_FIELD.NULL = fld_base_field.isEmpty();
					strcpy(RFR.RDB$BASE_FIELD, fld_base_field.c_str());
				}
			END_MODIFY;
		}
	END_FOR; // RFR IN RDB$RELATION_FIELDS
	CMP_release(tdbb, request);
	request = NULL;

	if (!found)
	{
		DYN_error_punt(false, 176, SafeArg() << orig_fld.dyn_fld_name.c_str() <<
						relation_name->c_str());
		// msg 176: "column %s does not exist in table/view %s"
	}

	// Update any indices that exist
	modify_lfield_index(tdbb, gbl, *relation_name, orig_fld.dyn_fld_name, orig_fld.dyn_fld_name);

	}
	catch (const Exception& ex)
	{
		stuff_exception(tdbb->tdbb_status_vector, ex);
		DYN_error_punt(true, 95);
		// msg 95: "MODIFY RDB$RELATION_FIELDS failed"
	}
}


// *************************************
// D Y N _ m o d i f y _ m a p p i n g
// *************************************
// It's purpose is to add/drop mapping from OS security name
// to DB security object
void DYN_modify_mapping(Global* gbl, const UCHAR** ptr)
{
	thread_db* tdbb = JRD_get_thread_data();
	Database* dbb = tdbb->getDatabase();

	jrd_req* request = CMP_find_request(tdbb, drq_m_map, DYN_REQUESTS);
	bool found = false;

	string osName, dbName;
	GET_STRING(ptr, osName);
	const UCHAR op = *(*ptr)++;
	GET_STRING(ptr, dbName);

	// This is FB 2.5 limited implementation!
	// Later it should work with new system table, something like RDB$MAPPING.

	if (dbName != ADMIN_ROLE)
	{
		status_exception::raise(Arg::Gds(isc_no_meta_update) << Arg::Gds(isc_wish_list));
	}

	if (!(tdbb->getAttachment() && tdbb->getAttachment()->locksmith()))
		ERR_post(Arg::Gds(isc_adm_task_denied));

	found = false;
	FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
		X IN RDB$ROLES
			WITH X.RDB$ROLE_NAME EQ dbName.c_str()

		if (!DYN_REQUEST(drq_m_map))
			DYN_REQUEST(drq_m_map) = request;

		found = true;
		MODIFY X
			switch (op)
			{
			case isc_dyn_automap_role:
				X.RDB$SYSTEM_FLAG = ROLE_FLAG_DBO | ROLE_FLAG_MAY_TRUST;
				break;

			case isc_dyn_autounmap_role:
				X.RDB$SYSTEM_FLAG = ROLE_FLAG_DBO;
				break;

			default:
				DYN_unsupported_verb();
			}
		END_MODIFY;
	END_FOR;

	if (!DYN_REQUEST(drq_m_map))
		DYN_REQUEST(drq_m_map) = request;

	if (!found)
	{
		status_exception::raise(Arg::Gds(isc_no_meta_update) <<
			Arg::Gds(isc_random) << Arg::Str("Missing RDB$ADMIN role in the database"));
	}
}

void get_domain_type(thread_db* tdbb, Global* gbl, dyn_fld& dom_fld)
{
/**************************************
 *
 *	g e t _ d o m a i n _ t y p e
 *
 **************************************
 *
 * Functional description
 *	Retrieves the type information for a domain so
 *      that it can be compared to a local field before
 *      modifying the datatype of a field.
 *
 **************************************/
	jrd_req* request = NULL;

	FOR(REQUEST_HANDLE request TRANSACTION_HANDLE gbl->gbl_transaction)
		FLD IN RDB$FIELDS WITH FLD.RDB$FIELD_NAME EQ dom_fld.dyn_fld_source.c_str();

		DSC_make_descriptor(&dom_fld.dyn_dsc,
							FLD.RDB$FIELD_TYPE,
							FLD.RDB$FIELD_SCALE,
							FLD.RDB$FIELD_LENGTH,
							FLD.RDB$FIELD_SUB_TYPE,
							FLD.RDB$CHARACTER_SET_ID,
							FLD.RDB$COLLATION_ID);

		dom_fld.dyn_charbytelen = FLD.RDB$FIELD_LENGTH;
		dom_fld.dyn_dtype = FLD.RDB$FIELD_TYPE;
		dom_fld.dyn_precision = FLD.RDB$FIELD_PRECISION;
		dom_fld.dyn_sub_type = FLD.RDB$FIELD_SUB_TYPE;
		dom_fld.dyn_charlen = FLD.RDB$CHARACTER_LENGTH;
		dom_fld.dyn_collation = FLD.RDB$COLLATION_ID;
		dom_fld.dyn_null_flag = FLD.RDB$NULL_FLAG != 0;

		if (!FLD.RDB$DIMENSIONS.NULL && FLD.RDB$DIMENSIONS > 0)
			dom_fld.dyn_dtype = blr_blob;

	END_FOR;
	CMP_release(tdbb, request);
}


static ULONG check_update_fld_type(const dyn_fld& orig_fld, const dyn_fld& new_fld)
{
/**************************************
 *
 *	c h e c k _ u p d a t e _ f l d _ t y p e
 *
 **************************************
 *
 * Functional description
 *	Compare the original field type with the new field type to
 *      determine if the original type can be changed to the new type
 *
 *  The following conversions are not allowed:
 *        Blob to anything
 *        Array to anything
 *        Date to anything
 *        Char to any numeric
 *        Varchar to any numeric
 *        Anything to Blob
 *        Anything to Array
 *
 *  This function returns an error code if the conversion can not be
 *  made.  If the conversion can be made, FB_SUCCESS is returned
 **************************************/


	// Check to make sure that the old and new types are compatible
	switch (orig_fld.dyn_dtype)
	{
	// CHARACTER types
	case blr_text:
	case blr_varying:
	case blr_cstring:
		switch (new_fld.dyn_dtype)
		{
		case blr_blob:
		case blr_blob_id:
			return isc_dyn_dtype_invalid;
			// Cannot change datatype for column %s.
			// The operation cannot be performed on BLOB, or ARRAY columns.
			break;

		case blr_sql_date:
		case blr_sql_time:
		case blr_timestamp:
		case blr_int64:
		case blr_long:
		case blr_short:
		case blr_d_float:
		case blr_double:
		case blr_float:
			return isc_dyn_dtype_conv_invalid;
			// Cannot convert column %s from character to non-character data.
			break;

			// If the original field is a character field and the new field is a character field,
			// is there enough space in the new field?
		case blr_text:
		case blr_varying:
		case blr_cstring:
			{
				// CVC: Because our caller invoked DSC_make_descriptor() on new_fld previously,
				// we should have the added bytes for varchar. For cstring, we are done, since
				// DSC_make_descriptor(DSC_string_length) != DSC_string_length(DSC_make_descriptor).

				const USHORT maxflen = DSC_string_length(&orig_fld.dyn_dsc);

				// We can have this assertion since this case is for both string fields.
				const ULONG new_len = DSC_string_length(&new_fld.dyn_dsc);
				fb_assert(new_len - maxflen == (ULONG) new_fld.dyn_charbytelen - orig_fld.dyn_charbytelen);
				// if (new_fld.dyn_dsc.dsc_length < maxflen)
				if (new_len < maxflen)
					return isc_dyn_char_fld_too_small;
				// msg 208: New size specified for column %s must be at least %d characters.
			}
			break;

		default:
			fb_assert(FALSE);
			return 87;			// MODIFY RDB$FIELDS FAILED
		}
		break;

	// BLOB and ARRAY types
	case blr_blob:
	case blr_blob_id:
		return isc_dyn_dtype_invalid;
		// Cannot change datatype for column %s.
		// The operation cannot be performed on BLOB, or ARRAY columns.

	// DATE types
	case blr_sql_date:
	case blr_sql_time:
	case blr_timestamp:
		switch (new_fld.dyn_dtype)
		{
		case blr_sql_date:
			if (orig_fld.dyn_dtype == blr_sql_time)
				return isc_dyn_invalid_dtype_conversion;
			// Cannot change datatype for column %s.  Conversion from base type %s to base type %s is not supported.
			break;

		case blr_sql_time:
			if (orig_fld.dyn_dtype == blr_sql_date)
				return isc_dyn_invalid_dtype_conversion;
			// Cannot change datatype for column %s.  Conversion from base type %s to base type %s is not supported.
			break;

		case blr_timestamp:
			if (orig_fld.dyn_dtype == blr_sql_time)
				return isc_dyn_invalid_dtype_conversion;
			// Cannot change datatype for column %s.  Conversion from base type %s to base type %s is not supported.
			break;

		// If the original field is a date field and the new field is a character field,
		// is there enough space in the new field?
		case blr_text:
		case blr_text2:
		case blr_varying:
		case blr_varying2:
		case blr_cstring:
		case blr_cstring2:
			{
				const USHORT maxflen = DSC_string_length(&orig_fld.dyn_dsc);

				// CVC: Solve bug #910423, missing DSC_string_length call.
				// if (new_fld.dyn_dsc.dsc_length < maxflen)
				if (DSC_string_length(&new_fld.dyn_dsc) < maxflen)
					return isc_dyn_char_fld_too_small;
				// msg 208: New size specified for column %s must be at least %d characters.
			}

			break;

		default:
			return isc_dyn_invalid_dtype_conversion;
			// Cannot change datatype for column %s.  Conversion from base type %s to base type %s is not supported.
		}
		break;

	// NUMERIC types
	case blr_int64:
	case blr_long:
	case blr_short:
	case blr_d_float:
	case blr_double:
	case blr_float:
		switch (new_fld.dyn_dtype)
		{
		case blr_blob:
		case blr_blob_id:
			return isc_dyn_dtype_invalid;
			// Cannot change datatype for column %s.
			// The operation cannot be performed on BLOB, or ARRAY columns.

		case blr_sql_date:
		case blr_sql_time:
		case blr_timestamp:
			return isc_dyn_invalid_dtype_conversion;
			// Cannot change datatype for column %s.  Conversion from base type %s to base type %s is not supported.

		// If the original field is a numeric field and the new field is a numeric field,
		// is there enough space in the new field (do not allow the base type to decrease)

		case blr_short:
			switch (orig_fld.dyn_dtype)
			{
			case blr_short:
				return check_update_numeric_type(orig_fld, new_fld);

			default:
				return isc_dyn_invalid_dtype_conversion;
				// Cannot change datatype for column %s.  Conversion from base type %s to base type %s is not supported.
			}
			break;

		case blr_long:
			switch (orig_fld.dyn_dtype)
			{
			case blr_long:
			case blr_short:
				return check_update_numeric_type(orig_fld, new_fld);

			default:
				return isc_dyn_invalid_dtype_conversion;
				// Cannot change datatype for column %s.  Conversion from base type %s to base type %s is not supported.
			}
			break;

		case blr_float:
			switch (orig_fld.dyn_dtype)
			{
			case blr_float:
			case blr_short:
				break;

			default:
				return isc_dyn_invalid_dtype_conversion;
				// Cannot change datatype for column %s.  Conversion from base type %s to base type %s is not supported.
			}
			break;

		case blr_int64:
			switch (orig_fld.dyn_dtype)
			{
			case blr_int64:
			case blr_long:
			case blr_short:
				return check_update_numeric_type(orig_fld, new_fld);

			default:
				return isc_dyn_invalid_dtype_conversion;
				// Cannot change datatype for column %s.  Conversion from base type %s to base type %s is not supported.
			}
			break;

		case blr_d_float:
		case blr_double:
			switch (orig_fld.dyn_dtype)
			{
			case blr_double:
			case blr_d_float:
			case blr_float:
			case blr_short:
			case blr_long:
				break;

			default:
				return isc_dyn_invalid_dtype_conversion;
				// Cannot change datatype for column %s.  Conversion from base type %s to base type %s is not supported.
			}
			break;

		// If the original field is a numeric field and the new field is a character field,
		// is there enough space in the new field?
		case blr_text:
		case blr_varying:
		case blr_cstring:
			{
				const USHORT maxflen = DSC_string_length(&orig_fld.dyn_dsc);

				// CVC: Solve bug #910423, missing DSC_string_length call.
				// if (new_fld.dyn_dsc.dsc_length < maxflen)
				if (DSC_string_length(&new_fld.dyn_dsc) < maxflen)
					return isc_dyn_char_fld_too_small;
				// msg 208: New size specified for column %s must be at least %d characters.
			}
			break;

		default:
			fb_assert(FALSE);
			return 87;			// MODIFY RDB$FIELDS FAILED
		}
		break;

	default:
		fb_assert(FALSE);
		return 87;				// MODIFY RDB$FIELDS FAILED
	}
	return FB_SUCCESS;
}


static ULONG check_update_numeric_type(const dyn_fld& orig_fld, const dyn_fld& new_fld)
{
/**************************************
 *
 *	c h e c k _ u p d a t e _ n u m e r i c _ t y p e
 *
 **************************************
 *
 * Functional description
 *	Compare the original field type with the new field type to
 *      determine if the original type can be changed to the new type.
 *  The types should be integral, since it tests only numeric/decimal subtypes
 *      to ensure the scale is not being widened at the expense of the precision,
 *      because the old stored values should fit in the new definition.
 *
 *  This function returns an error code if the conversion can not be
 *  made.  If the conversion can be made, FB_SUCCESS is returned.
 **************************************/

 	// Since dsc_scale is negative, the sum of precision and scale produces
	// the width of the integral part.
	if (orig_fld.dyn_sub_type && new_fld.dyn_sub_type &&
		orig_fld.dyn_precision + orig_fld.dyn_dsc.dsc_scale >
			new_fld.dyn_precision + new_fld.dyn_dsc.dsc_scale)
	{
		return isc_dyn_scale_too_big;
	}
	return FB_SUCCESS;
}


static void modify_err_punt(thread_db* /*tdbb*/,
							ULONG errorcode,
							const dyn_fld& orig_fld_def,
							const dyn_fld& new_fld_def)
{
/**************************************
 *
 *	m o d i f y _ e r r _ p u n t
 *
 **************************************
 *
 * Functional description
 *	A generic error routine that calls DYN_error_punt
 *      based on the error code returned by check_update_field_type.
 *
 *      This function is called by DYN_modify_global_field and by
 *	DYN_modify_sql_field
 **************************************/

	switch (errorcode)
	{
	case isc_dyn_dtype_invalid:
		DYN_error_punt(false, errorcode, orig_fld_def.dyn_fld_name.c_str());
		// Cannot change datatype for column %s.The operation cannot be performed on DATE, BLOB, or ARRAY columns.
		break;

	case isc_dyn_dtype_conv_invalid:
		DYN_error_punt(false, errorcode, orig_fld_def.dyn_fld_name.c_str());
		// Cannot convert column %s from character to non-character data.
		break;

	case isc_dyn_char_fld_too_small:
		DYN_error_punt(false,
						errorcode,
						SafeArg() << orig_fld_def.dyn_fld_name.c_str() <<
						DSC_string_length(&orig_fld_def.dyn_dsc));
		// msg 208: New size specified for column %s must be at least %d characters.
		break;

	case isc_dyn_scale_too_big:
		{
			int code = errorcode;
			int diff = new_fld_def.dyn_precision -
				(orig_fld_def.dyn_precision + orig_fld_def.dyn_dsc.dsc_scale);
			if (diff < 0)
			{
				// If new scale becomes negative externally, the message is useless for the user.
				// (The scale is always zero or negative for us but externally is non-negative.)
				// Let's ask the user to widen the precision, then. Example: numeric(4, 0) -> numeric(1, 1).
				code = isc_dyn_precision_too_small;
				diff = new_fld_def.dyn_precision - new_fld_def.dyn_dsc.dsc_scale - diff;
			}
			DYN_error_punt(false, code, SafeArg() << orig_fld_def.dyn_fld_name.c_str() << diff);
			// scale_too_big: New scale specified for column @1 must be at most @2.
			// precision_too_small: New precision specified for column @1 must be at least @2.
		}
		break;

	case isc_dyn_invalid_dtype_conversion:
		{
			TEXT orig_type[25], new_type[25];

			DSC_get_dtype_name(&orig_fld_def.dyn_dsc, orig_type, sizeof(orig_type));
			DSC_get_dtype_name(&new_fld_def.dyn_dsc, new_type, sizeof(new_type));

			DYN_error_punt(false, errorcode,
							SafeArg() << orig_fld_def.dyn_fld_name.c_str() <<
							orig_type << new_type);
			// Cannot change datatype for @1.  Conversion from base type @2 to @3 is not supported.
		}
		break;

	default:
		DYN_error_punt(true, 95);
		// msg 95: "MODIFY RDB$RELATION_FIELDS failed"
	}
}