Feature CORE-5463 - Support GENERATED ALWAYS identity columns and OVERRIDE clause.

I didn't verified why the error messages are being truncated. It seems idiotic if
the engine, library or ISQL does not accept these not-so-detailed messages.

doc/sql.extensions/README.identity_columns.txt

@@ -11,16 +11,20 @@ Description:
 
 Syntax:
     <column definition> ::=
-        <name> <type> GENERATED BY DEFAULT AS IDENTITY [ ( <identity column option>... ) ] <constraints>
+        <name> <type> GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY [ ( <identity column option>... ) ] <constraints>
 
     <identity column option> ::=
         START WITH <value> |
         INCREMENT [ BY ] <value>
 
     <alter column definition> ::=
+        <name> <set identity column generation clause> [ <alter identity column option>... ] |
         <name> <alter identity column option>... |
         <name> DROP IDENTITY
 
+    <set identity column generation clause> ::=
+        SET GENERATED { ALWAYS | BY DEFAULT }
+
     <alter identity column option> ::=
         RESTART [ WITH <value> ] |
         SET INCREMENT [ BY ] <value>
@@ -39,10 +43,8 @@ Notes:
 Implementation:
     Two columns have been inserted in RDB$RELATION_FIELDS: RDB$GENERATOR_NAME and RDB$IDENTITY_TYPE.
     RDB$GENERATOR_NAME stores the automatically created generator for the column. In RDB$GENERATORS,
-    the value of RDB$SYSTEM_FLAG of that generator will be 6. RDB$IDENTITY_TYPE will currently
+    the value of RDB$SYSTEM_FLAG of that generator will be 6. RDB$IDENTITY_TYPE stores the value
-    always store the value 1 (by default) for identity columns and NULL for non-identity columns.
+	0 for GENERATED ALWAYS, 1 for GENERATED BY DEFAULT, and NULL for non-identity columns.
-    In the future this column will store the value 0, too (for ALWAYS) when Firebird support this type
-    of identity column.
 
 Example:
 
@@ -84,3 +86,21 @@ alter table objects
 
 alter table objects
   alter id drop identity;
+
+
+---------------
+Override Clause
+---------------
+
+BY DEFAULT identity columns can be overriden in INSERT statements (INSERT, UPDATE OR INSERT, MERGE ... WHEN NOT MATCHED)
+just specifying the value in the values list. However, for ALWAYS identity columns that is not allowed.
+
+To use the value passed in the INSERT statement for an ALWAYS column, you should pass OVERRIDING SYSTEM VALUE as
+following:
+
+insert into objects (id, name) overriding system value values (11, 'Laptop');
+
+OVERRIDING also supports a subclause to be used with BY DEFAULT columns, to ignore the value passed in INSERT and use
+the defined sequence:
+
+insert into objects (id, name) overriding user value values (12, 'Laptop');  -- 12 is not used

lang_helpers/gds_codes.ftn

@@ -1678,6 +1678,14 @@ C --
       PARAMETER (GDS__att_shut_db_down                 = 335545132)
       INTEGER*4 GDS__att_shut_engine                 
       PARAMETER (GDS__att_shut_engine                  = 335545133)
+      INTEGER*4 GDS__overriding_without_identity     
+      PARAMETER (GDS__overriding_without_identity      = 335545134)
+      INTEGER*4 GDS__overriding_system_invalid       
+      PARAMETER (GDS__overriding_system_invalid        = 335545135)
+      INTEGER*4 GDS__overriding_user_invalid         
+      PARAMETER (GDS__overriding_user_invalid          = 335545136)
+      INTEGER*4 GDS__overriding_system_missing       
+      PARAMETER (GDS__overriding_system_missing        = 335545137)
       INTEGER*4 GDS__gfix_db_name                    
       PARAMETER (GDS__gfix_db_name                     = 335740929)
       INTEGER*4 GDS__gfix_invalid_sw                 

lang_helpers/gds_codes.pas

@@ -1673,6 +1673,14 @@ const
 	gds_att_shut_db_down                 = 335545132;
 	isc_att_shut_engine                  = 335545133;
 	gds_att_shut_engine                  = 335545133;
+	isc_overriding_without_identity      = 335545134;
+	gds_overriding_without_identity      = 335545134;
+	isc_overriding_system_invalid        = 335545135;
+	gds_overriding_system_invalid        = 335545135;
+	isc_overriding_user_invalid          = 335545136;
+	gds_overriding_user_invalid          = 335545136;
+	isc_overriding_system_missing        = 335545137;
+	gds_overriding_system_missing        = 335545137;
 	isc_gfix_db_name                     = 335740929;
 	gds_gfix_db_name                     = 335740929;
 	isc_gfix_invalid_sw                  = 335740930;

src/common/classes/Nullable.h

@@ -35,7 +35,7 @@ class NullableClear
 public:
 	static void clear(T& v)
 	{
-		v = 0;
+		v = T();
 	}
 };
 
@@ -70,6 +70,11 @@ public:
 		return (!specified && !o.specified) || (specified == o.specified && value == o.value);
 	}
 
+	bool operator ==(const T& o) const
+	{
+		return specified && value == o;
+	}
+
 	void operator =(const T& v)
 	{
 		this->value = v;
@@ -84,26 +89,6 @@ public:
 
 // NullableClear specializations.
 
-template <>
-class NullableClear<Firebird::string>	// string especialization for NullableClear
-{
-public:
-	static void clear(Firebird::string& v)
-	{
-		v = "";
-	}
-};
-
-template <>
-class NullableClear<Firebird::MetaName>	// MetaName especialization for NullableClear
-{
-public:
-	static void clear(Firebird::MetaName& v)
-	{
-		v = "";
-	}
-};
-
 template <typename T>
 class NullableClear<BaseNullable<T> >
 {

src/dsql/DdlNodes.epp

@@ -5951,7 +5951,7 @@ void RelationNode::FieldDefinition::store(thread_db* tdbb, jrd_tra* transaction)
 			strcpy(RFR.RDB$GENERATOR_NAME, identitySequence.c_str());
 
 			RFR.RDB$IDENTITY_TYPE.NULL = FALSE;
-			RFR.RDB$IDENTITY_TYPE = IDENT_TYPE_BY_DEFAULT;
+			RFR.RDB$IDENTITY_TYPE = identityType.value;
 		}
 
 		if (notNullFlag.specified)
@@ -6296,6 +6296,7 @@ void RelationNode::defineField(thread_db* tdbb, DsqlCompilerScratch* dsqlScratch
 			}
 
 			DYN_UTIL_generate_generator_name(tdbb, fieldDefinition.identitySequence);
+			fieldDefinition.identityType = clause->identityOptions->type;
 
 			CreateAlterSequenceNode::store(tdbb, transaction, fieldDefinition.identitySequence,
 				fb_sysflag_identity_generator,
@@ -7858,6 +7859,13 @@ void AlterRelationNode::modifyField(thread_db* tdbb, DsqlCompilerScratch* dsqlSc
 						transaction->getGenIdCache()->put(id, val);
 					}
 
+					if (clause->identityOptions->type.specified)
+					{
+						MODIFY RFR
+							RFR.RDB$IDENTITY_TYPE = clause->identityOptions->type.value;
+						END_MODIFY
+					}
+
 					if (clause->identityOptions->increment.specified)
 					{
 						if (clause->identityOptions->increment.value == 0)

src/dsql/DdlNodes.h

@@ -1140,6 +1140,7 @@ public:
 		Firebird::MetaName relationName;
 		Firebird::MetaName fieldSource;
 		Firebird::MetaName identitySequence;
+		Nullable<IdentityType> identityType;
 		Nullable<USHORT> collationId;
 		Nullable<bool> notNullFlag;	// true = NOT NULL / false = NULL
 		Nullable<USHORT> position;
@@ -1306,11 +1307,18 @@ public:
 
 	struct IdentityOptions
 	{
+		IdentityOptions(MemoryPool&, IdentityType aType)
+			: type(aType),
+			  restart(false)
+		{
+		}
+
 		IdentityOptions(MemoryPool&)
 			: restart(false)
 		{
 		}
 
+		Nullable<IdentityType> type;
 		Nullable<SINT64> startValue;
 		Nullable<SLONG> increment;
 		bool restart;	// used in ALTER

src/dsql/StmtNodes.cpp

@@ -94,6 +94,8 @@ static void postTriggerAccess(CompilerScratch* csb, jrd_rel* ownerRelation,
 	ExternalAccess::exa_act operation, jrd_rel* view);
 static void preModifyEraseTriggers(thread_db* tdbb, TrigVector** trigs,
 	StmtNode::WhichTrigger whichTrig, record_param* rpb, record_param* rec, TriggerAction op);
+static void preprocessAssignments(thread_db* tdbb, CompilerScratch* csb,
+	StreamType stream, CompoundStmtNode* compoundNode, const Nullable<OverrideClause>* insertOverride);
 static void validateExpressions(thread_db* tdbb, const Array<ValidateInfo>& validations);
 
 }	// namespace Jrd
@@ -5340,6 +5342,7 @@ StmtNode* MergeNode::dsqlPass(DsqlCompilerScratch* dsqlScratch)
 		store->dsqlRelation = relation;
 		store->dsqlFields = notMatched->fields;
 		store->dsqlValues = notMatched->values;
+		store->overrideClause = notMatched->overrideClause;
 
 		bool needSavePoint; // unused
 		thisIf->trueAction = store = store->internalDsqlPass(dsqlScratch, false, needSavePoint)->as<StoreNode>();
@@ -5881,50 +5884,7 @@ void ModifyNode::genBlr(DsqlCompilerScratch* dsqlScratch)
 
 ModifyNode* ModifyNode::pass1(thread_db* tdbb, CompilerScratch* csb)
 {
-	CompoundStmtNode* compoundNode = statement->as<CompoundStmtNode>();
+	preprocessAssignments(tdbb, csb, newStream, statement->as<CompoundStmtNode>(), NULL);
-
-	// Remove assignments of DEFAULT to computed fields.
-	if (compoundNode)
-	{
-		for (size_t i = compoundNode->statements.getCount(); i--; )
-		{
-			const AssignmentNode* assign = compoundNode->statements[i]->as<AssignmentNode>();
-			fb_assert(assign);
-			if (!assign)
-				continue;
-
-			const ExprNode* assignFrom = assign->asgnFrom;
-			const FieldNode* assignToField = assign->asgnTo->as<FieldNode>();
-
-			if (assignToField && assignFrom->is<DefaultNode>())
-			{
-				jrd_rel* relation = csb->csb_rpt[newStream].csb_relation;
-				int fieldId = assignToField->fieldId;
-
-				while (true)
-				{
-					jrd_fld* fld;
-
-					if (assignToField->fieldStream == newStream &&
-						relation &&
-						relation->rel_fields &&
-						(fld = (*relation->rel_fields)[fieldId]))
-					{
-						if (fld->fld_computation)
-							compoundNode->statements.remove(i);
-						else if (relation->rel_view_rse && fld->fld_source_rel_field.first.hasData())
-						{
-							relation = MET_lookup_relation(tdbb, fld->fld_source_rel_field.first);
-							if ((fieldId = MET_lookup_field(tdbb, relation, fld->fld_source_rel_field.second)) >= 0)
-								continue;
-						}
-					}
-
-					break;
-				}
-			}
-		}
-	}
 
 	pass1Modify(tdbb, csb, this);
 
@@ -6463,6 +6423,7 @@ const StmtNode* ReceiveNode::execute(thread_db* /*tdbb*/, jrd_req* request, ExeS
 
 static RegisterNode<StoreNode> regStoreNode(blr_store);
 static RegisterNode<StoreNode> regStoreNode2(blr_store2);
+static RegisterNode<StoreNode> regStoreNode3(blr_store3);
 
 // Parse a store statement.
 DmlNode* StoreNode::parse(thread_db* tdbb, MemoryPool& pool, CompilerScratch* csb, const UCHAR blrOp)
@@ -6471,6 +6432,21 @@ DmlNode* StoreNode::parse(thread_db* tdbb, MemoryPool& pool, CompilerScratch* cs
 
 	AutoSetRestore<StmtNode*> autoCurrentDMLNode(&csb->csb_currentDMLNode, node);
 
+	if (blrOp == blr_store3)
+	{
+		node->overrideClause = static_cast<OverrideClause>(csb->csb_blr_reader.getByte());
+
+		switch (node->overrideClause.value)
+		{
+			case OverrideClause::USER_VALUE:
+			case OverrideClause::SYSTEM_VALUE:
+				break;
+
+			default:
+				PAR_syntax_error(csb, "invalid blr_store3 override clause");
+		}
+	}
+
 	const UCHAR* blrPos = csb->csb_blr_reader.getPos();
 
 	node->relationSource = PAR_parseRecordSource(tdbb, csb)->as<RelationSourceNode>();
@@ -6485,6 +6461,13 @@ DmlNode* StoreNode::parse(thread_db* tdbb, MemoryPool& pool, CompilerScratch* cs
 
 	if (blrOp == blr_store2)
 		node->statement2 = PAR_parse_stmt(tdbb, csb);
+	else if (blrOp == blr_store3)
+	{
+		if (csb->csb_blr_reader.peekByte() == blr_null)
+			csb->csb_blr_reader.getByte();
+		else
+			node->statement2 = PAR_parse_stmt(tdbb, csb);
+	}
 
 	return node;
 }
@@ -6498,6 +6481,7 @@ StmtNode* StoreNode::internalDsqlPass(DsqlCompilerScratch* dsqlScratch,
 	dsqlScratch->getStatement()->setType(DsqlCompiledStatement::TYPE_INSERT);
 
 	StoreNode* node = FB_NEW_POOL(getPool()) StoreNode(getPool());
+	node->overrideClause = overrideClause;
 
 	// Process SELECT expression, if present
 
@@ -6606,7 +6590,21 @@ StmtNode* StoreNode::internalDsqlPass(DsqlCompilerScratch* dsqlScratch,
 		NestConst<ValueExprNode>* ptr2 = values->items.begin();
 		for (const NestConst<ValueExprNode>* end = fields.end(); ptr != end; ++ptr, ++ptr2)
 		{
-			if (*ptr2)	// it's NULL for DEFAULT
+			// *ptr2 is NULL for DEFAULT
+
+			if (!*ptr2)
+			{
+				const FieldNode* field = (*ptr)->as<FieldNode>();
+
+				if (field && field->dsqlField)
+				{
+					*ptr2 = FB_NEW_POOL(getPool()) DefaultNode(getPool(),
+						relation->rel_name, field->dsqlField->fld_name);
+					*ptr2 = doDsqlPass(dsqlScratch, *ptr2, false);
+				}
+			}
+
+			if (*ptr2)
 			{
 				AssignmentNode* temp = FB_NEW_POOL(getPool()) AssignmentNode(getPool());
 				temp->asgnFrom = *ptr2;
@@ -6691,12 +6689,19 @@ void StoreNode::genBlr(DsqlCompilerScratch* dsqlScratch)
 {
 	const dsql_msg* message = dsqlGenDmlHeader(dsqlScratch, dsqlRse->as<RseNode>());
 
-	dsqlScratch->appendUChar(statement2 ? blr_store2 : blr_store);
+	dsqlScratch->appendUChar(overrideClause.specified ? blr_store3 : (statement2 ? blr_store2 : blr_store));
+
+	if (overrideClause.specified)
+		dsqlScratch->appendUChar(UCHAR(overrideClause.value));
+
 	GEN_expr(dsqlScratch, dsqlRelation);
+
 	statement->genBlr(dsqlScratch);
 
 	if (statement2)
 		statement2->genBlr(dsqlScratch);
+	else if (overrideClause.specified)
+		dsqlScratch->appendUChar(blr_null);
 
 	if (message)
 		dsqlScratch->appendUChar(blr_end);
@@ -6704,6 +6709,8 @@ void StoreNode::genBlr(DsqlCompilerScratch* dsqlScratch)
 
 StoreNode* StoreNode::pass1(thread_db* tdbb, CompilerScratch* csb)
 {
+	preprocessAssignments(tdbb, csb, relationSource->getStream(), statement->as<CompoundStmtNode>(), &overrideClause);
+
 	if (pass1Store(tdbb, csb, this))
 		makeDefaults(tdbb, csb);
 
@@ -6839,7 +6846,6 @@ void StoreNode::makeDefaults(thread_db* tdbb, CompilerScratch* csb)
 	}
 
 	StmtNodeStack stack;
-
 	USHORT fieldId = 0;
 	vec<jrd_fld*>::iterator ptr1 = vector->begin();
 
@@ -6869,10 +6875,7 @@ void StoreNode::makeDefaults(thread_db* tdbb, CompilerScratch* csb)
 					fb_assert(fieldNode);
 
 					if (fieldNode && fieldNode->fieldStream == stream && fieldNode->fieldId == fieldId)
-					{
-						inList = true;
 						break;
-					}
 				}
 			}
 
@@ -8071,6 +8074,7 @@ StmtNode* UpdateOrInsertNode::dsqlPass(DsqlCompilerScratch* dsqlScratch)
 	insert->dsqlFields = fields;
 	insert->dsqlValues = values;
 	insert->dsqlReturning = returning;
+	insert->overrideClause = overrideClause;
 	insert = insert->internalDsqlPass(dsqlScratch, true, needSavePoint)->as<StoreNode>();
 	fb_assert(insert);
 
@@ -9324,6 +9328,99 @@ static void preModifyEraseTriggers(thread_db* tdbb, TrigVector** trigs,
 	tdbb->getTransaction()->tra_rpblist->PopRpb(rpb, rpblevel);
 }
 
+// 1. Remove assignments of DEFAULT to computed fields.
+// 2. Remove assignments to identity column when OVERRIDING USER VALUE is specified in INSERT.
+static void preprocessAssignments(thread_db* tdbb, CompilerScratch* csb,
+	StreamType stream, CompoundStmtNode* compoundNode, const Nullable<OverrideClause>* insertOverride)
+{
+	if (!compoundNode)
+		return;
+
+	jrd_rel* relation = csb->csb_rpt[stream].csb_relation;
+
+	fb_assert(relation);
+	if (!relation)
+		return;
+
+	Nullable<IdentityType> identityType;
+
+	for (size_t i = compoundNode->statements.getCount(); i--; )
+	{
+		const AssignmentNode* assign = compoundNode->statements[i]->as<AssignmentNode>();
+		fb_assert(assign);
+		if (!assign)
+			continue;
+
+		const ExprNode* assignFrom = assign->asgnFrom;
+		const FieldNode* assignToField = assign->asgnTo->as<FieldNode>();
+
+		if (assignToField)
+		{
+			int fieldId = assignToField->fieldId;
+			jrd_fld* fld;
+
+			while (true)
+			{
+				if (assignToField->fieldStream == stream &&
+					relation->rel_fields &&
+					(fld = (*relation->rel_fields)[fieldId]))
+				{
+					if (insertOverride && fld->fld_identity_type.specified)
+					{
+						if (insertOverride->specified || !assignFrom->is<DefaultNode>())
+							identityType = fld->fld_identity_type;
+
+						if (*insertOverride == OverrideClause::USER_VALUE)
+						{
+							compoundNode->statements.remove(i);
+							break;
+						}
+					}
+
+					if (fld->fld_computation)
+					{
+						if (assignFrom->is<DefaultNode>())
+							compoundNode->statements.remove(i);
+					}
+					else if (relation->rel_view_rse && fld->fld_source_rel_field.first.hasData())
+					{
+						relation = MET_lookup_relation(tdbb, fld->fld_source_rel_field.first);
+
+						fb_assert(relation);
+						if (!relation)
+							return;
+
+						if ((fieldId = MET_lookup_field(tdbb, relation, fld->fld_source_rel_field.second)) >= 0)
+							continue;
+					}
+				}
+
+				break;
+			}
+		}
+	}
+
+	if (!insertOverride)
+		return;
+
+	if (insertOverride->specified)
+	{
+		if (!identityType.specified)
+			ERR_post(Arg::Gds(isc_overriding_without_identity) << relation->rel_name);
+
+		if (identityType == IDENT_TYPE_BY_DEFAULT && *insertOverride == OverrideClause::SYSTEM_VALUE)
+			ERR_post(Arg::Gds(isc_overriding_system_invalid) << relation->rel_name);
+
+		if (identityType == IDENT_TYPE_ALWAYS && *insertOverride == OverrideClause::USER_VALUE)
+			ERR_post(Arg::Gds(isc_overriding_user_invalid) << relation->rel_name);
+	}
+	else
+	{
+		if (identityType == IDENT_TYPE_ALWAYS)
+			ERR_post(Arg::Gds(isc_overriding_system_missing) << relation->rel_name);
+	}
+}
+
 // Execute a list of validation expressions.
 static void validateExpressions(thread_db* tdbb, const Array<ValidateInfo>& validations)
 {

src/dsql/StmtNodes.h

@@ -112,6 +112,14 @@ struct ValidateInfo
 };
 
 
+enum OverrideClause : UCHAR
+{
+	// Warning: used in BLR
+	USER_VALUE = 1,
+	SYSTEM_VALUE
+};
+
+
 class AssignmentNode : public TypedNode<StmtNode, StmtNode::TYPE_ASSIGNMENT>
 {
 public:
@@ -1048,6 +1056,7 @@ public:
 		Firebird::Array<NestConst<FieldNode> > fields;
 		NestConst<ValueListNode> values;
 		NestConst<BoolExprNode> condition;
+		Nullable<OverrideClause> overrideClause;
 	};
 
 	explicit MergeNode(MemoryPool& pool)
@@ -1267,6 +1276,7 @@ public:
 	NestConst<StmtNode> subStore;
 	Firebird::Array<ValidateInfo> validations;
 	NestConst<RelationSourceNode> relationSource;
+	Nullable<OverrideClause> overrideClause;
 };
 
 
@@ -1609,6 +1619,7 @@ public:
 	NestConst<ValueListNode> values;
 	Firebird::Array<NestConst<FieldNode> > matching;
 	NestConst<ReturningClause> returning;
+	Nullable<OverrideClause> overrideClause;
 };
 
 

src/dsql/parse-conflicts.txt

@@ -1 +1 @@
-45 shift/reduce conflicts, 17 reduce/reduce conflicts.
+46 shift/reduce conflicts, 17 reduce/reduce conflicts.

src/dsql/parse.y

@@ -600,6 +600,7 @@ using namespace Firebird;
 %token <metaNamePtr> MESSAGE
 %token <metaNamePtr> NTILE
 %token <metaNamePtr> OTHERS
+%token <metaNamePtr> OVERRIDING
 %token <metaNamePtr> PERCENT_RANK
 %token <metaNamePtr> PRECEDING
 %token <metaNamePtr> PRIVILEGE
@@ -648,6 +649,7 @@ using namespace Firebird;
 	BaseNullable<int> nullableIntVal;
 	BaseNullable<bool> nullableBoolVal;
 	BaseNullable<Jrd::TriggerDefinition::SqlSecurity> nullableSqlSecurityVal;
+	BaseNullable<Jrd::OverrideClause> nullableOverrideClause;
 	bool boolVal;
 	int intVal;
 	unsigned uintVal;
@@ -727,6 +729,7 @@ using namespace Firebird;
 	Jrd::RelationNode::RefActionClause* refActionClause;
 	Jrd::RelationNode::IndexConstraintClause* indexConstraintClause;
 	Jrd::RelationNode::IdentityOptions* identityOptions;
+	IdentityType identityType;
 	Jrd::CreateRelationNode* createRelationNode;
 	Jrd::CreateAlterViewNode* createAlterViewNode;
 	Jrd::CreateIndexNode* createIndexNode;
@@ -2185,10 +2188,16 @@ column_def($relationNode)
 
 %type <identityOptions> identity_clause
 identity_clause
-	: GENERATED BY DEFAULT AS IDENTITY
+	: GENERATED identity_clause_type AS IDENTITY
-			{ $$ = newNode<RelationNode::IdentityOptions>(); }
+			{ $$ = newNode<RelationNode::IdentityOptions>($2); }
-		identity_clause_options_opt($6)
+		identity_clause_options_opt($5)
-			{ $$ = $6; }
+			{ $$ = $5; }
+	;
+
+%type <identityType> identity_clause_type
+identity_clause_type
+	: BY DEFAULT	{ $$ = IDENT_TYPE_BY_DEFAULT; }
+	| ALWAYS		{ $$ = IDENT_TYPE_ALWAYS; }
 	;
 
 %type identity_clause_options_opt(<identityOptions>)
@@ -3935,7 +3944,7 @@ alter_op($relationNode)
 		}
 	| col_opt symbol_column_name
 			{ $<identityOptions>$ = newNode<RelationNode::IdentityOptions>(); }
-		alter_identity_clause_options($<identityOptions>3)
+		alter_identity_clause_spec($<identityOptions>3)
 			{
 				RelationNode::AlterColTypeClause* clause = newNode<RelationNode::AlterColTypeClause>();
 				clause->field = newNode<dsql_fld>();
@@ -4081,6 +4090,24 @@ alter_data_type_or_domain
 		}
 	;
 
+%type alter_identity_clause_spec(<identityOptions>)
+alter_identity_clause_spec($identityOptions)
+	: alter_identity_clause_generation($identityOptions) alter_identity_clause_options_opt($identityOptions)
+	| alter_identity_clause_options($identityOptions)
+	;
+
+%type alter_identity_clause_generation(<identityOptions>)
+alter_identity_clause_generation($identityOptions)
+	: SET GENERATED ALWAYS			{ $identityOptions->type = IDENT_TYPE_ALWAYS; }
+	| SET GENERATED BY DEFAULT		{ $identityOptions->type = IDENT_TYPE_BY_DEFAULT; }
+	;
+
+%type alter_identity_clause_options_opt(<identityOptions>)
+alter_identity_clause_options_opt($identityOptions)
+	: // nothing
+	| alter_identity_clause_options($identityOptions)
+	;
+
 %type alter_identity_clause_options(<identityOptions>)
 alter_identity_clause_options($identityOptions)
 	: alter_identity_clause_options alter_identity_clause_option($identityOptions)
@@ -5942,18 +5969,20 @@ fetch_first_clause
 // IBO hack: replace column_parens_opt by ins_column_parens_opt.
 %type <storeNode> insert
 insert
-	: insert_start ins_column_parens_opt(NOTRIAL(&$1->dsqlFields)) VALUES '(' value_or_default_list ')'
+	: insert_start ins_column_parens_opt(NOTRIAL(&$1->dsqlFields)) override_opt VALUES '(' value_or_default_list ')'
 			returning_clause
 		{
 			StoreNode* node = $$ = $1;
-			node->dsqlValues = $5;
+			node->overrideClause = $3;
-			node->dsqlReturning = $7;
+			node->dsqlValues = $6;
+			node->dsqlReturning = $8;
 		}
-	| insert_start ins_column_parens_opt(NOTRIAL(&$1->dsqlFields)) select_expr returning_clause
+	| insert_start ins_column_parens_opt(NOTRIAL(&$1->dsqlFields)) override_opt select_expr returning_clause
 		{
 			StoreNode* node = $$ = $1;
-			node->dsqlRse = $3;
+			node->overrideClause = $3;
-			node->dsqlReturning = $4;
+			node->dsqlRse = $4;
+			node->dsqlReturning = $5;
 			$$ = node;
 		}
 	| insert_start DEFAULT VALUES returning_clause
@@ -5974,6 +6003,13 @@ insert_start
 		}
 	;
 
+%type <nullableOverrideClause> override_opt
+override_opt
+	: /* nothing */				{ $$ = Nullable<OverrideClause>::empty(); }
+	| OVERRIDING USER VALUE		{ $$ = Nullable<OverrideClause>::val(OverrideClause::USER_VALUE); }
+	| OVERRIDING SYSTEM VALUE	{ $$ = Nullable<OverrideClause>::val(OverrideClause::SYSTEM_VALUE); }
+	;
+
 %type <valueListNode> value_or_default_list
 value_or_default_list
 	: value_or_default								{ $$ = newNode<ValueListNode>($1); }
@@ -6042,13 +6078,17 @@ merge_update_specification($mergeMatchedClause, $relationName)
 
 %type merge_insert_specification(<mergeNotMatchedClause>)
 merge_insert_specification($mergeNotMatchedClause)
-	: THEN INSERT ins_column_parens_opt(NOTRIAL(&$mergeNotMatchedClause->fields))
+	: THEN INSERT ins_column_parens_opt(NOTRIAL(&$mergeNotMatchedClause->fields)) override_opt
-			VALUES '(' value_or_default_list ')'
-		{ $mergeNotMatchedClause->values = $6; }
-	| AND search_condition THEN INSERT ins_column_parens_opt(NOTRIAL(&$mergeNotMatchedClause->fields))
 			VALUES '(' value_or_default_list ')'
 		{
-			$mergeNotMatchedClause->values = $8;
+			$mergeNotMatchedClause->overrideClause = $4;
+			$mergeNotMatchedClause->values = $7;
+		}
+	| AND search_condition THEN INSERT ins_column_parens_opt(NOTRIAL(&$mergeNotMatchedClause->fields)) override_opt
+			VALUES '(' value_or_default_list ')'
+		{
+			$mergeNotMatchedClause->overrideClause = $6;
+			$mergeNotMatchedClause->values = $9;
 			$mergeNotMatchedClause->condition = $2;
 		}
 	;
@@ -6138,12 +6178,13 @@ update_or_insert
 				UpdateOrInsertNode* node = $$ = newNode<UpdateOrInsertNode>();
 				node->relation = $5;
 			}
-		ins_column_parens_opt(NOTRIAL(&$6->fields)) VALUES '(' value_or_default_list ')'
+		ins_column_parens_opt(NOTRIAL(&$6->fields)) override_opt VALUES '(' value_or_default_list ')'
 				update_or_insert_matching_opt(NOTRIAL(&$6->matching)) returning_clause
 			{
 				UpdateOrInsertNode* node = $$ = $6;
-				node->values = $10;
+				node->overrideClause = $8;
-				node->returning = $13;
+				node->values = $11;
+				node->returning = $14;
 			}
 	;
 
@@ -8248,6 +8289,7 @@ non_reserved_word
 	| MESSAGE
 	| NTILE
 	| OTHERS
+	| OVERRIDING
 	| PERCENT_RANK
 	| PRECEDING
 	| PRIVILEGE

src/include/gen/codetext.h

@@ -835,6 +835,10 @@ static const struct {
 	{"att_shut_idle", 335545131},
 	{"att_shut_db_down", 335545132},
 	{"att_shut_engine", 335545133},
+	{"overriding_without_identity", 335545134},
+	{"overriding_system_invalid", 335545135},
+	{"overriding_user_invalid", 335545136},
+	{"overriding_system_missing", 335545137},
 	{"gfix_db_name", 335740929},
 	{"gfix_invalid_sw", 335740930},
 	{"gfix_incmp_sw", 335740932},

src/include/gen/iberror.h

@@ -869,6 +869,10 @@ const ISC_STATUS isc_att_shut_killed                  = 335545130L;
 const ISC_STATUS isc_att_shut_idle                    = 335545131L;
 const ISC_STATUS isc_att_shut_db_down                 = 335545132L;
 const ISC_STATUS isc_att_shut_engine                  = 335545133L;
+const ISC_STATUS isc_overriding_without_identity      = 335545134L;
+const ISC_STATUS isc_overriding_system_invalid        = 335545135L;
+const ISC_STATUS isc_overriding_user_invalid          = 335545136L;
+const ISC_STATUS isc_overriding_system_missing        = 335545137L;
 const ISC_STATUS isc_gfix_db_name                     = 335740929L;
 const ISC_STATUS isc_gfix_invalid_sw                  = 335740930L;
 const ISC_STATUS isc_gfix_incmp_sw                    = 335740932L;
@@ -1343,7 +1347,7 @@ const ISC_STATUS isc_trace_switch_user_only           = 337182757L;
 const ISC_STATUS isc_trace_switch_param_miss          = 337182758L;
 const ISC_STATUS isc_trace_param_act_notcompat        = 337182759L;
 const ISC_STATUS isc_trace_mandatory_switch_miss      = 337182760L;
-const ISC_STATUS isc_err_max                          = 1287;
+const ISC_STATUS isc_err_max                          = 1291;
 
 #else /* c definitions */
 
@@ -2182,6 +2186,10 @@ const ISC_STATUS isc_err_max                          = 1287;
 #define isc_att_shut_idle                    335545131L
 #define isc_att_shut_db_down                 335545132L
 #define isc_att_shut_engine                  335545133L
+#define isc_overriding_without_identity      335545134L
+#define isc_overriding_system_invalid        335545135L
+#define isc_overriding_user_invalid          335545136L
+#define isc_overriding_system_missing        335545137L
 #define isc_gfix_db_name                     335740929L
 #define isc_gfix_invalid_sw                  335740930L
 #define isc_gfix_incmp_sw                    335740932L
@@ -2656,7 +2664,7 @@ const ISC_STATUS isc_err_max                          = 1287;
 #define isc_trace_switch_param_miss          337182758L
 #define isc_trace_param_act_notcompat        337182759L
 #define isc_trace_mandatory_switch_miss      337182760L
-#define isc_err_max                          1287
+#define isc_err_max                          1291
 
 #endif
 

src/include/gen/msgs.h

@@ -838,6 +838,10 @@ Data source : @4"},		/* eds_statement */
 	{335545131, "Idle timeout expired."},		/* att_shut_idle */
 	{335545132, "Database is shutdown."},		/* att_shut_db_down */
 	{335545133, "Engine is shutdown."},		/* att_shut_engine */
+	{335545134, "OVERRIDING clause can be used only when an identity column is present in the INSERT's field list for table/view @1"},		/* overriding_without_identity */
+	{335545135, "OVERRIDING SYSTEM VALUE can be used only for identity column defined as 'GENERATED ALWAYS' in INSERT for table/view @1"},		/* overriding_system_invalid */
+	{335545136, "OVERRIDING USER VALUE can be used only for identity column defined as 'GENERATED BY DEFAULT' in INSERT for table/view"},		/* overriding_user_invalid */
+	{335545137, "OVERRIDING SYSTEM VALUE should be used to override the value of an identity column defined as 'GENERATED ALWAYS' in ta"},		/* overriding_system_missing */
 	{335740929, "data base file name (@1) already given"},		/* gfix_db_name */
 	{335740930, "invalid switch @1"},		/* gfix_invalid_sw */
 	{335740932, "incompatible switch combination"},		/* gfix_incmp_sw */

src/include/gen/sql_code.h

@@ -834,6 +834,10 @@ static const struct {
 	{335545131, -902}, /* 811 att_shut_idle */
 	{335545132, -902}, /* 812 att_shut_db_down */
 	{335545133, -902}, /* 813 att_shut_engine */
+	{335545134, -902}, /* 814 overriding_without_identity */
+	{335545135, -902}, /* 815 overriding_system_invalid */
+	{335545136, -902}, /* 816 overriding_user_invalid */
+	{335545137, -902}, /* 817 overriding_system_missing */
 	{335740929, -901}, /*   1 gfix_db_name */
 	{335740930, -901}, /*   2 gfix_invalid_sw */
 	{335740932, -901}, /*   4 gfix_incmp_sw */

src/include/gen/sql_state.h

@@ -834,6 +834,10 @@ static const struct {
 	{335545131, "08003"}, // 811 att_shut_idle
 	{335545132, "08003"}, // 812 att_shut_db_down
 	{335545133, "08003"}, // 813 att_shut_engine
+	{335545134, "42000"}, // 814 overriding_without_identity
+	{335545135, "42000"}, // 815 overriding_system_invalid
+	{335545136, "42000"}, // 816 overriding_user_invalid
+	{335545137, "42000"}, // 817 overriding_system_missing
 	{335740929, "00000"}, //   1 gfix_db_name
 	{335740930, "00000"}, //   2 gfix_invalid_sw
 	{335740932, "00000"}, //   4 gfix_incmp_sw

src/isql/extract.epp

@@ -496,7 +496,9 @@ int EXTRACT_list_table(const SCHAR* relation_name,
 			FOR GEN IN RDB$GENERATORS
 				WITH GEN.RDB$GENERATOR_NAME = RFR.RDB$GENERATOR_NAME
 			{
-				isqlGlob.printf(" GENERATED BY DEFAULT AS IDENTITY");
+				isqlGlob.printf(" GENERATED %s AS IDENTITY",
+					(RFR.RDB$IDENTITY_TYPE == IDENT_TYPE_BY_DEFAULT ? "BY DEFAULT" :
+					 RFR.RDB$IDENTITY_TYPE == IDENT_TYPE_ALWAYS ? "ALWAYS" : ""));
 
 				if (!GEN.RDB$INITIAL_VALUE.NULL && GEN.RDB$INITIAL_VALUE != 0)
 					isqlGlob.printf(" (START WITH %" SQUADFORMAT ")", GEN.RDB$INITIAL_VALUE);

src/isql/show.epp

@@ -5838,7 +5838,11 @@ static processing_state show_table(const SCHAR* relation_name, bool isView)
 		}
 
 		if (!RFR.RDB$GENERATOR_NAME.NULL)
-			isqlGlob.printf("Identity (by default)");
+		{
+			isqlGlob.printf("Identity (%s)",
+				(RFR.RDB$IDENTITY_TYPE == IDENT_TYPE_BY_DEFAULT ? "by default" :
+				 RFR.RDB$IDENTITY_TYPE == IDENT_TYPE_ALWAYS ? "always" : ""));
+		}
 
 		// Handle defaults for columns
 

src/jrd/Relation.h

@@ -485,6 +485,7 @@ public:
 	Firebird::MetaName	fld_security_name;	// security class name for field
 	Firebird::MetaName	fld_generator_name;	// identity generator name
 	Firebird::MetaNamePair	fld_source_rel_field;	// Relation/field source name
+	Nullable<IdentityType> fld_identity_type;
 
 public:
 	explicit jrd_fld(MemoryPool& p)

src/jrd/blp.h

@@ -243,5 +243,6 @@ static const struct
 	{"gen_id2", gen_id2}, // 210
 	{"window_win", window_win},
 	{"default", relation_field},
+	{"store3", store3},
 	{0, 0}
 };

src/jrd/blr.h

@@ -421,5 +421,6 @@
 #define blr_window_win_exclusion			(unsigned char) 7
 
 #define blr_default					(unsigned char) 212
+#define blr_store3					(unsigned char) 213
 
 #endif // JRD_BLR_H

src/jrd/dfw.epp

@@ -5754,6 +5754,10 @@ static bool make_version(thread_db* tdbb, SSHORT phase, DeferredWork* work, jrd_
 										   (UCHAR*) RFR.RDB$GENERATOR_NAME, n);
 					}
 
+					n = RFR.RDB$IDENTITY_TYPE;
+					if (!RFR.RDB$IDENTITY_TYPE.NULL)
+						put_summary_record(tdbb, blob, RSR_field_identity_type, (UCHAR*) &n, sizeof(n));
+
 					// Make a temporary field block
 
 					TemporaryField* tfb = FB_NEW_POOL(*tdbb->getDefaultPool()) TemporaryField;

src/jrd/filters.cpp

@@ -449,6 +449,10 @@ ISC_STATUS filter_runtime(USHORT action, BlobControl* control)
 		sprintf(line, "    field_generator_name: %s", p);
 		break;
 
+	case RSR_field_identity_type:
+		sprintf(line, "Field identity type: %d", n);
+		break;
+
 	default:
 		sprintf(line, "*** unknown verb %d ***", (int) buff[0]);
 	}

src/jrd/met.epp

@@ -4046,6 +4046,12 @@ void MET_scan_relation(thread_db* tdbb, jrd_rel* relation)
 
 			case RSR_field_generator_name:
 				field->fld_generator_name = (const TEXT*) p;
+				if (!field->fld_identity_type.specified)
+					field->fld_identity_type = IDENT_TYPE_BY_DEFAULT;
+				break;
+
+			case RSR_field_identity_type:
+				field->fld_identity_type = static_cast<IdentityType>(n);
 				break;
 
 			default:    // Shut up compiler warning

src/jrd/met.h

@@ -50,7 +50,8 @@ enum rsr_t {
 	RSR_field_length,
 	RSR_field_sub_type,
 	RSR_field_not_null,
-	RSR_field_generator_name
+	RSR_field_generator_name,
+	RSR_field_identity_type
 };
 
 // Temporary field block

src/msgs/facilities2.sql

@@ -1,7 +1,7 @@
 /* MAX_NUMBER is the next number to be used, always one more than the highest message number. */
 set bulk_insert INSERT INTO FACILITIES (LAST_CHANGE, FACILITY, FAC_CODE, MAX_NUMBER) VALUES (?, ?, ?, ?);
 --
-('2016-12-20 12:57:00', 'JRD', 0, 814)
+('2017-02-24 22:00:00', 'JRD', 0, 818)
 ('2015-03-17 18:33:00', 'QLI', 1, 533)
 ('2015-01-07 18:01:51', 'GFIX', 3, 134)
 ('1996-11-07 13:39:40', 'GPRE', 4, 1)

src/msgs/messages2.sql

@@ -921,6 +921,10 @@ Data source : @4', NULL, NULL)
 ('att_shut_idle', NULL, 'jrd.cpp', NULL, 0, 811, NULL, 'Idle timeout expired.', NULL, NULL);
 ('att_shut_db_down', NULL, 'jrd.cpp', NULL, 0, 812, NULL, 'Database is shutdown.', NULL, NULL);
 ('att_shut_engine', NULL, 'jrd.cpp', NULL, 0, 813, NULL, 'Engine is shutdown.', NULL, NULL);
+('overriding_without_identity', NULL, 'StmtNodes.cpp', NULL, 0, 814, NULL, 'OVERRIDING clause can be used only when an identity column is present in the INSERT''s field list for table/view @1', NULL, NULL);
+('overriding_system_invalid', NULL, 'StmtNodes.cpp', NULL, 0, 815, NULL, 'OVERRIDING SYSTEM VALUE can be used only for identity column defined as ''GENERATED ALWAYS'' in INSERT for table/view @1', NULL, NULL);
+('overriding_user_invalid', NULL, 'StmtNodes.cpp', NULL, 0, 816, NULL, 'OVERRIDING USER VALUE can be used only for identity column defined as ''GENERATED BY DEFAULT'' in INSERT for table/view @1', NULL, NULL);
+('overriding_system_missing', NULL, 'StmtNodes.cpp', NULL, 0, 817, NULL, 'OVERRIDING SYSTEM VALUE should be used to override the value of an identity column defined as ''GENERATED ALWAYS'' in table/view @1', NULL, NULL);
 -- QLI
 (NULL, NULL, NULL, NULL, 1, 0, NULL, 'expected type', NULL, NULL);
 (NULL, NULL, NULL, NULL, 1, 1, NULL, 'bad block type', NULL, NULL);

src/msgs/system_errors2.sql

@@ -820,6 +820,10 @@ set bulk_insert INSERT INTO SYSTEM_ERRORS (SQL_CODE, SQL_CLASS, SQL_SUBCLASS, FA
 (-902, '08', '003', 0, 811, 'att_shut_idle', NULL, NULL)
 (-902, '08', '003', 0, 812, 'att_shut_db_down', NULL, NULL)
 (-902, '08', '003', 0, 813, 'att_shut_engine', NULL, NULL)
+(-902, '42', '000', 0, 814, 'overriding_without_identity', NULL, NULL)
+(-902, '42', '000', 0, 815, 'overriding_system_invalid', NULL, NULL)
+(-902, '42', '000', 0, 816, 'overriding_user_invalid', NULL, NULL)
+(-902, '42', '000', 0, 817, 'overriding_system_missing', NULL, NULL)
 -- GFIX
 (-901, '00', '000', 3, 1, 'gfix_db_name', NULL, NULL)
 (-901, '00', '000', 3, 2, 'gfix_invalid_sw', NULL, NULL)

src/yvalve/gds.cpp

@@ -344,7 +344,8 @@ static const UCHAR
 	subfunc_decl[] = { op_subfunc_decl, 0},
 	window_win[] = { op_byte, op_window_win, 0},
 	relation_field[] = { op_line, op_indent, op_byte, op_literal,
-						 op_line, op_indent, op_byte, op_literal, op_pad, op_line, 0};
+						 op_line, op_indent, op_byte, op_literal, op_pad, op_line, 0},
+	store3[] = { op_line, op_byte, op_line, op_verb, op_verb, op_verb, 0};
 
 
 #include "../jrd/blp.h"

src/yvalve/keywords.cpp

@@ -309,6 +309,7 @@ static const TOK tokens[] =
 	{TOK_OVER, "OVER", false},
 	{TOK_OVERFLOW, "OVERFLOW", true},
 	{TOK_OVERLAY, "OVERLAY", true},
+	{TOK_OVERRIDING, "OVERRIDING", true},
 	{TOK_PACKAGE, "PACKAGE", true},
 	{TOK_PAD, "PAD", true},
 	{TOK_PAGE, "PAGE", true},