Improvement #7590 - Improve DECLARE VARIABLE to accept complete value expressions. (#7608)

doc/sql.extensions/README.declare_var_initializer.md

@@ -0,0 +1,68 @@
+# DECLARE VARIABLE initializer enhancements (FB 6.0)
+
+Up to Firebird 5.0, variables could be declared and initialized in the same statement, however only simple
+expressions (the same as allowed in a DOMAIN's DEFAULT clause) were allowed as initializers.
+This limitation has been removed in Firebird 6.0, allowing the use of any value expression as initializer.
+
+## Syntax
+
+```
+DECLARE [VARIABLE] <varname> <type> [{ = | DEFAULT } <value>];
+```
+
+## Notes
+
+Previously declared variables can be used in the initializer expression of following variables.
+
+A variable initializer may call subroutines, and these subroutines may read and write previously
+declared variables.
+
+A subroutine used in an initializer may also write to variables declared after the one being
+initialized, but in this case their values will be overwritten when their initializers are
+executed, even if they don't have explicit initializers.
+
+```
+-- This block will return (<null>, 2) as values of v1 and v2 assigned in sf1 will
+-- be overwritten by their initializer after sf1 is called.
+execute block returns (o1 integer, o2 integer)
+as
+    declare function sf1 returns integer;
+
+    declare v0 integer = sf1();
+    declare v1 integer;
+    declare v2 integer = 2;
+
+    declare function sf1 returns integer
+    as
+    begin
+        v1 = 10;
+        v2 = 20;
+        return 0;
+    end
+begin
+    o1 = v1;
+    o2 = v2;
+    suspend;
+end
+```
+
+It's an error if a subroutine reads a variable declared after the one being initialized like in the
+following example.
+
+```
+-- When sf1 is called, v1 is not yet initialized.
+execute block
+as
+    declare function sf1 returns integer;
+
+    declare v0 integer = sf1();
+    declare v1 integer;
+
+    declare function sf1 returns integer
+    as
+    begin
+        return v1;
+    end
+begin
+end
+```

src/dsql/DdlNodes.epp

@@ -2323,7 +2323,7 @@ void CreateAlterFunctionNode::compile(thread_db* /*tdbb*/, DsqlCompilerScratch*
 		}
 
 		dsql_var* const variable = dsqlScratch->outputVariables[0];
-		dsqlScratch->putLocalVariable(variable, 0, NULL);
+		dsqlScratch->putLocalVariable(variable, nullptr, {});
 
 		// ASF: This is here to not change the old logic (proc_flag)
 		// of previous calls to PASS1_node and PASS1_statement.
@@ -3193,7 +3193,7 @@ void CreateAlterProcedureNode::compile(thread_db* /*tdbb*/, DsqlCompilerScratch*
 		 i != dsqlScratch->outputVariables.end();
 		 ++i)
 	{
-		dsqlScratch->putLocalVariable(*i, 0, NULL);
+		dsqlScratch->putLocalVariable(*i, nullptr, {});
 	}
 
 	// ASF: This is here to not change the old logic (proc_flag)

src/dsql/DsqlCompilerScratch.cpp

@@ -289,26 +289,24 @@ void DsqlCompilerScratch::putLocalVariables(CompoundStmtNode* parameters, USHORT
 	if (!parameters)
 		return;
 
-	NestConst<StmtNode>* ptr = parameters->statements.begin();
+	Array<dsql_var*> declaredVariables;
 
-	for (const NestConst<StmtNode>* const end = parameters->statements.end(); ptr != end; ++ptr)
+	const auto end = parameters->statements.end();
+
+	for (auto ptr = parameters->statements.begin(); ptr != end; ++ptr)
 	{
-		StmtNode* parameter = *ptr;
+		auto parameter = *ptr;
 
 		putDebugSrcInfo(parameter->line, parameter->column);
 
-		DeclareVariableNode* varNode;
-
-		if ((varNode = nodeAs<DeclareVariableNode>(parameter)))
+		if (const auto varNode = nodeAs<DeclareVariableNode>(parameter))
 		{
 			dsql_fld* field = varNode->dsqlDef->type;
 			const NestConst<StmtNode>* rest = ptr;
 
 			while (++rest != end)
 			{
-				const DeclareVariableNode* varNode2;
-
-				if ((varNode2 = nodeAs<DeclareVariableNode>(*rest)))
+				if (const auto varNode2 = nodeAs<DeclareVariableNode>(*rest))
 				{
 					const dsql_fld* rest_field = varNode2->dsqlDef->type;
 
@@ -320,10 +318,10 @@ void DsqlCompilerScratch::putLocalVariables(CompoundStmtNode* parameters, USHORT
 				}
 			}
 
-			dsql_var* variable = makeVariable(field, field->fld_name.c_str(), dsql_var::TYPE_LOCAL,
-				0, 0, locals);
+			const auto variable = makeVariable(field, field->fld_name.c_str(), dsql_var::TYPE_LOCAL, 0, 0, locals);
+			declaredVariables.add(variable);
 
-			putLocalVariable(variable, varNode, varNode->dsqlDef->type->collate);
+			putLocalVariableDecl(variable, varNode, varNode->dsqlDef->type->collate);
 
 			// Some field attributes are calculated inside putLocalVariable(), so we reinitialize
 			// the descriptor.
@@ -342,6 +340,14 @@ void DsqlCompilerScratch::putLocalVariables(CompoundStmtNode* parameters, USHORT
 			fb_assert(false);
 	}
 
+	auto declVarIt = declaredVariables.begin();
+
+	for (const auto parameter : parameters->statements)
+	{
+		if (const auto varNode = nodeAs<DeclareVariableNode>(parameter))
+			putLocalVariableInit(*declVarIt++, varNode);
+	}
+
 	if (!(flags & DsqlCompilerScratch::FLAG_SUB_ROUTINE))
 	{
 		// Check not implemented sub-functions.
@@ -369,22 +375,38 @@ void DsqlCompilerScratch::putLocalVariables(CompoundStmtNode* parameters, USHORT
 }
 
 // Write out local variable field data type.
-void DsqlCompilerScratch::putLocalVariable(dsql_var* variable, const DeclareVariableNode* hostParam,
+void DsqlCompilerScratch::putLocalVariableDecl(dsql_var* variable, DeclareVariableNode* hostParam,
 	const MetaName& collationName)
 {
-	dsql_fld* field = variable->field;
+	const auto field = variable->field;
 
 	appendUChar(blr_dcl_variable);
 	appendUShort(variable->number);
 	DDL_resolve_intl_type(this, field, collationName);
 
-	//const USHORT dtype = field->dtype;
-
 	putDtype(field, true);
-	//field->dtype = dtype;
+
+	if (variable->field->fld_name.hasData())	// Not a function return value
+		putDebugVariable(variable->number, variable->field->fld_name);
+
+	++hiddenVarsNumber;
+
+	if (variable->type != dsql_var::TYPE_INPUT && hostParam && hostParam->dsqlDef->defaultClause)
+	{
+		hostParam->dsqlDef->defaultClause->value =
+			Node::doDsqlPass(this, hostParam->dsqlDef->defaultClause->value, true);
+	}
+
+	variable->initialized = true;
+}
+
+// Write out local variable initialization.
+void DsqlCompilerScratch::putLocalVariableInit(dsql_var* variable, const DeclareVariableNode* hostParam)
+{
+	const dsql_fld* field = variable->field;
 
 	// Check for a default value, borrowed from define_domain
-	NestConst<ValueSourceClause> node = hostParam ? hostParam->dsqlDef->defaultClause : NULL;
+	NestConst<ValueSourceClause> node = hostParam ? hostParam->dsqlDef->defaultClause : nullptr;
 
 	if (variable->type == dsql_var::TYPE_INPUT)
 	{
@@ -405,7 +427,7 @@ void DsqlCompilerScratch::putLocalVariable(dsql_var* variable, const DeclareVari
 		appendUChar(blr_assignment);
 
 		if (node)
-			GEN_expr(this, Node::doDsqlPass(this, node->value, false));
+			GEN_expr(this, node->value);
 		else
 			appendUChar(blr_null);	// Initialize variable to NULL
 
@@ -417,11 +439,6 @@ void DsqlCompilerScratch::putLocalVariable(dsql_var* variable, const DeclareVari
 		appendUChar(blr_init_variable);
 		appendUShort(variable->number);
 	}
-
-	if (variable->field->fld_name.hasData())	// Not a function return value
-		putDebugVariable(variable->number, variable->field->fld_name);
-
-	++hiddenVarsNumber;
 }
 
 // Put maps in subroutines for outer variables/parameters usage.

src/dsql/DsqlCompilerScratch.h

@@ -181,8 +181,15 @@ public:
 	void putDtype(const TypeClause* field, bool useSubType);
 	void putType(const TypeClause* type, bool useSubType);
 	void putLocalVariables(CompoundStmtNode* parameters, USHORT locals);
-	void putLocalVariable(dsql_var* variable, const DeclareVariableNode* hostParam,
-		const MetaName& collationName);
+	void putLocalVariableDecl(dsql_var* variable, DeclareVariableNode* hostParam, const MetaName& collationName);
+	void putLocalVariableInit(dsql_var* variable, const DeclareVariableNode* hostParam);
+
+	void putLocalVariable(dsql_var* variable, DeclareVariableNode* hostParam, const MetaName& collationName)
+	{
+		putLocalVariableDecl(variable, hostParam, collationName);
+		putLocalVariableInit(variable, hostParam);
+	}
+
 	void putOuterMaps();
 	dsql_var* makeVariable(dsql_fld*, const char*, const dsql_var::Type type, USHORT,
 		USHORT, USHORT);

src/dsql/ExprNodes.cpp

@@ -13703,8 +13703,11 @@ ValueExprNode* VariableNode::dsqlPass(DsqlCompilerScratch* dsqlScratch)
 		}
 	}
 
-	if (!node->dsqlVar)
+	if (!node->dsqlVar ||
+		(node->dsqlVar->type == dsql_var::TYPE_LOCAL && !node->dsqlVar->initialized && !dsqlScratch->mainScratch))
+	{
 		PASS1_field_unknown(NULL, dsqlName.c_str(), this);
+	}
 
 	return node;
 }
@@ -13844,6 +13847,15 @@ dsc* VariableNode::execute(thread_db* tdbb, Request* request) const
 	const auto varRequest = getVarRequest(request);
 	const auto varImpure = varRequest->getImpure<impure_value>(varDecl->impureOffset);
 
+	if (!(varImpure->vlu_flags & VLU_initialized))
+	{
+		const Item item(Item::TYPE_VARIABLE, varId);
+
+		//// FIXME: Variable with simple type has no varInfo.
+		const auto s = item.getDescription(request, varInfo);
+		ERR_post(Arg::Gds(isc_uninitialized_var) << s);
+	}
+
 	request->req_flags &= ~req_null;
 
 	dsc* desc;

src/dsql/StmtNodes.cpp

@@ -4254,9 +4254,11 @@ const StmtNode* InitVariableNode::execute(thread_db* tdbb, Request* request, Exe
 {
 	if (request->req_operation == Request::req_evaluate)
 	{
+		const auto varImpure = request->getImpure<impure_value>(varDecl->impureOffset);
+
 		if (varInfo)
 		{
-			dsc* toDesc = &request->getImpure<impure_value>(varDecl->impureOffset)->vlu_desc;
+			dsc* toDesc = &varImpure->vlu_desc;
 			toDesc->dsc_flags |= DSC_null;
 
 			MapFieldInfo::ValueType fieldInfo;
@@ -4275,6 +4277,8 @@ const StmtNode* InitVariableNode::execute(thread_db* tdbb, Request* request, Exe
 			}
 		}
 
+		varImpure->vlu_flags |= VLU_initialized;
+
 		request->req_operation = Request::req_return;
 	}
 
@@ -4497,10 +4501,10 @@ void ExecBlockNode::genBlr(DsqlCompilerScratch* dsqlScratch)
 		}
 	}
 
-	Array<dsql_var*>& variables = subRoutine ? dsqlScratch->outputVariables : dsqlScratch->variables;
+	const Array<dsql_var*>& variables = subRoutine ? dsqlScratch->outputVariables : dsqlScratch->variables;
 
-	for (Array<dsql_var*>::const_iterator i = variables.begin(); i != variables.end(); ++i)
-		dsqlScratch->putLocalVariable(*i, 0, NULL);
+	for (const auto variable : variables)
+		dsqlScratch->putLocalVariable(variable, nullptr, {});
 
 	dsqlScratch->setPsql(true);
 

src/dsql/dsql.h

@@ -386,21 +386,17 @@ public:
 
 public:
 	explicit dsql_var(MemoryPool& p)
-		: PermanentStorage(p),
-		  field(NULL),
-		  type(TYPE_INPUT),
-		  msgNumber(0),
-		  msgItem(0),
-		  number(0)
+		: PermanentStorage(p)
 	{
 		desc.clear();
 	}
 
-	dsql_fld* field;	// Field on which variable is based
-	Type type;			// Input, output, local or hidden variable
-	USHORT msgNumber;	// Message number containing variable
-	USHORT msgItem;		// Item number in message
-	USHORT number;		// Local variable number
+	dsql_fld* field = nullptr;	// Field on which variable is based
+	Type type = TYPE_INPUT;		// Input, output, local or hidden variable
+	USHORT msgNumber = 0;		// Message number containing variable
+	USHORT msgItem = 0;			// Item number in message
+	USHORT number = 0;			// Local variable number
+	bool initialized = false;	// Is variable initialized?
 	dsc desc;
 };
 

src/dsql/parse.y

@@ -3158,7 +3158,7 @@ local_declaration_item
 
 %type <stmtNode> var_declaration_item
 var_declaration_item
-	: column_domain_or_non_array_type collate_clause default_par_opt
+	: column_domain_or_non_array_type collate_clause var_declaration_initializer
 		{
 			DeclareVariableNode* node = newNode<DeclareVariableNode>();
 			node->dsqlDef = newNode<ParameterClause>($1, optName($2), $3);
@@ -3166,6 +3166,26 @@ var_declaration_item
 		}
 	;
 
+%type <valueSourceClause> var_declaration_initializer
+var_declaration_initializer
+	: // nothing
+		{ $$ = nullptr; }
+	| DEFAULT value
+		{
+			const auto clause = newNode<ValueSourceClause>();
+			clause->value = $2;
+			clause->source = makeParseStr(YYPOSNARG(1), YYPOSNARG(2));
+			$$ = clause;
+		}
+	| '=' value
+		{
+			const auto clause = newNode<ValueSourceClause>();
+			clause->value = $2;
+			clause->source = makeParseStr(YYPOSNARG(1), YYPOSNARG(2));
+			$$ = clause;
+		}
+	;
+
 var_decl_opt
 	: // nothing
 	| VARIABLE

src/include/firebird/impl/msg/jrd.h

@@ -968,3 +968,4 @@ FB_IMPL_MSG(JRD, 965, ods_upgrade_err, -901, "HY", "000", "ODS upgrade failed wh
 FB_IMPL_MSG(JRD, 966, bad_par_workers, -924, "HY", "000", "Wrong parallel workers value @1, valid range are from 1 to @2")
 FB_IMPL_MSG(JRD, 967, idx_expr_not_found, -902, "42", "000", "Definition of index expression is not found for index @1")
 FB_IMPL_MSG(JRD, 968, idx_cond_not_found, -902, "42", "000", "Definition of index condition is not found for index @1")
+FB_IMPL_MSG(JRD, 969, uninitialized_var, -625, "42", "000", "Variable @1 is not initialized")

src/jrd/evl.cpp

@@ -677,41 +677,8 @@ void EVL_validate(thread_db* tdbb, const Item& item, const ItemInfo* itemInfo, d
 		}
 		else
 		{
-			if (itemInfo->name.isEmpty())
-			{
-				int index = item.index + 1;
-
-				status = isc_not_valid_for;
-
-				if (item.type == Item::TYPE_VARIABLE)
-				{
-					const jrd_prc* procedure = request->getStatement()->procedure;
-
-					if (procedure)
-					{
-						if (index <= int(procedure->getOutputFields().getCount()))
-							s.printf("output parameter number %d", index);
-						else
-						{
-							s.printf("variable number %d",
-								index - int(procedure->getOutputFields().getCount()));
-						}
-					}
-					else
-						s.printf("variable number %d", index);
-				}
-				else if (item.type == Item::TYPE_PARAMETER && item.subType == 0)
-					s.printf("input parameter number %d", (index - 1) / 2 + 1);
-				else if (item.type == Item::TYPE_PARAMETER && item.subType == 1)
-					s.printf("output parameter number %d", index);
-
-				if (s.isEmpty())
-					arg = UNKNOWN_STRING_MARK;
-				else
-					arg = s.c_str();
-			}
-			else
-				arg = itemInfo->name.c_str();
+			s = item.getDescription(request, itemInfo);
+			arg = s.c_str();
 		}
 
 		ERR_post(Arg::Gds(status) << Arg::Str(arg) << Arg::Str(value));

src/jrd/exe.cpp

@@ -115,6 +115,44 @@
 using namespace Jrd;
 using namespace Firebird;
 
+// Item class implementation
+
+string Item::getDescription(Request* request, const ItemInfo* itemInfo) const
+{
+	if (itemInfo && itemInfo->name.hasData())
+		return itemInfo->name.c_str();
+
+	int oneBasedIndex = index + 1;
+	string s;
+
+	if (type == Item::TYPE_VARIABLE)
+	{
+		const auto* const procedure = request->getStatement()->procedure;
+
+		if (procedure)
+		{
+			if (oneBasedIndex <= int(procedure->getOutputFields().getCount()))
+				s.printf("[output parameter number %d]", oneBasedIndex);
+			else
+			{
+				s.printf("[number %d]",
+					oneBasedIndex - int(procedure->getOutputFields().getCount()));
+			}
+		}
+		else
+			s.printf("[number %d]", oneBasedIndex);
+	}
+	else if (type == Item::TYPE_PARAMETER && subType == 0)
+		s.printf("[input parameter number %d]", (oneBasedIndex - 1) / 2 + 1);
+	else if (type == Item::TYPE_PARAMETER && subType == 1)
+		s.printf("[output parameter number %d]", oneBasedIndex);
+
+	if (s.isEmpty())
+		s = UNKNOWN_STRING_MARK;
+
+	return s;
+}
+
 // AffectedRows class implementation
 
 AffectedRows::AffectedRows()
@@ -327,8 +365,8 @@ void EXE_assignment(thread_db* tdbb, const ValueExprNode* to, dsc* from_desc, bo
 			toVar->varDecl->impureOffset)->vlu_flags;
 	}
 
-	if (impure_flags != NULL)
-		*impure_flags |= VLU_checked;
+	if (impure_flags)
+		*impure_flags |= VLU_initialized | VLU_checked;
 
 	// If the value is non-missing, move/convert it.  Otherwise fill the
 	// field with appropriate nulls.

src/jrd/exe.h

@@ -81,6 +81,7 @@ class Cursor;
 class DeclareSubFuncNode;
 class DeclareSubProcNode;
 class DeclareVariableNode;
+class ItemInfo;
 class MessageNode;
 class PlanNode;
 class RecordSource;
@@ -357,6 +358,8 @@ struct Item
 
 		return type > x.type;
 	}
+
+	Firebird::string getDescription(Request* request, const ItemInfo* itemInfo) const;
 };
 
 struct FieldInfo

src/jrd/val.h

@@ -229,9 +229,10 @@ struct impure_value_ex : public impure_value
 	blb* vlu_blob;
 };
 
-const int VLU_computed	= 1;	// An invariant sub-query has been computed
-const int VLU_null		= 2;	// An invariant sub-query computed to null
-const int VLU_checked	= 4;	// Constraint already checked in first read or assignment to argument/variable
+const int VLU_computed		= 1;	// An invariant sub-query has been computed
+const int VLU_null			= 2;	// An invariant sub-query computed to null
+const int VLU_checked		= 4;	// Constraint already checked in first read or assignment to argument/variable
+const int VLU_initialized	= 8;	// Variable initialized
 
 
 class Format : public pool_alloc<type_fmt>