Feature #8062 - CREATE IF NOT EXISTS. (#8072)

Author: asfernandes

doc/sql.extensions/README.ddl.txt

@@ -664,5 +664,43 @@ DROP USER [IF EXISTS] <user> [USING PLUGIN <plugin>]
 DROP PACKAGE [IF EXISTS] <package>
 DROP PACKAGE BODY [IF EXISTS] <package>
 DROP [GLOBAL] MAPPING [IF EXISTS] <mapping>
-ALTER TABLE <table> DROP [IF EXISTS] <column>
-ALTER TABLE <table> DROP CONSTRAINT [IF EXISTS] <constraint>
+ALTER TABLE <table> DROP [IF EXISTS] <column name>
+ALTER TABLE <table> DROP CONSTRAINT [IF EXISTS] <constraint name>
+
+2) CREATE [IF NOT EXISTS]
+
+Using subclause IF NOT EXISTS, it's now possible to try to create objects and do not get errors when they
+already exists.
+
+For ALTER TABLE ... ADD subclause, DDL triggers are not fired if there are only IF NOT EXISTS subclauses and all
+of them are related to existing columns or constraints.
+
+For others commands where IF NOT EXISTS is part of the main command, DDL triggers are not fired when the object
+already exists.
+
+The engine only verifies if the name (object, column or constraint) already exists, and if yes, do nothing.
+It never tries to match the existing object with the one being created.
+
+The following statements are supported:
+
+CREATE EXCEPTION [IF NOT EXISTS] ...
+CREATE INDEX [IF NOT EXISTS] ...
+CREATE PROCEDURE [IF NOT EXISTS] ...
+CREATE TABLE [IF NOT EXISTS] ...
+CREATE TRIGGER [IF NOT EXISTS] ...
+CREATE VIEW [IF NOT EXISTS] ...
+CREATE FILTER [IF NOT EXISTS] ...
+CREATE DOMAIN [IF NOT EXISTS] ...
+CREATE FUNCTION [IF NOT EXISTS] ...
+DECLARE EXTERNAL FUNCTION [IF NOT EXISTS] ...
+CREATE SHADOW [IF NOT EXISTS] ...
+CREATE ROLE [IF NOT EXISTS] ...
+CREATE GENERATOR [IF NOT EXISTS] ...
+CREATE SEQUENCE [IF NOT EXISTS] ...
+CREATE COLLATION [IF NOT EXISTS] ...
+CREATE USER [IF NOT EXISTS] ...
+CREATE PACKAGE [IF NOT EXISTS] ...
+CREATE PACKAGE BODY [IF NOT EXISTS] ...
+CREATE [GLOBAL] MAPPING [IF NOT EXISTS] ...
+ALTER TABLE <table> ADD [IF NOT EXISTS] <column name> ...
+ALTER TABLE <table> ADD CONSTRAINT [IF NOT EXISTS] <constraint name> ...

src/common/security.h

@@ -220,6 +220,7 @@ class UserData :
 	unsigned int op;
 	int trustedAuth;
 	bool silent;
+	bool createIfNotExistsOnly = false;
 	CharField user, pass, first, last, middle, com, attr;
 	IntField adm, act;
 	CharField database, dba, dbaPassword, role;

src/dsql/DdlNodes.epp

@@ -1789,6 +1789,9 @@ void CreateAlterFunctionNode::executeCreate(thread_db* tdbb, DsqlCompilerScratch
 
 	if (package.isEmpty())
 	{
+		if (createIfNotExistsOnly && !DYN_UTIL_check_unique_name_nothrow(tdbb, transaction, name, obj_udf))
+			return;
+
 		executeDdlTrigger(tdbb, dsqlScratch, transaction, DTW_BEFORE,
 			DDL_TRIGGER_CREATE_FUNCTION, name, NULL);
 
@@ -2804,6 +2807,9 @@ void CreateAlterProcedureNode::executeCreate(thread_db* tdbb, DsqlCompilerScratc
 
 	if (package.isEmpty())
 	{
+		if (createIfNotExistsOnly && !DYN_UTIL_check_unique_name_nothrow(tdbb, transaction, name, obj_procedure))
+			return;
+
 		executeDdlTrigger(tdbb, dsqlScratch, transaction, DTW_BEFORE,
 			DDL_TRIGGER_CREATE_PROCEDURE, name, NULL);
 
@@ -3724,9 +3730,14 @@ void CreateAlterTriggerNode::execute(thread_db* tdbb, DsqlCompilerScratch* dsqlS
 void CreateAlterTriggerNode::executeCreate(thread_db* tdbb, DsqlCompilerScratch* dsqlScratch,
 	jrd_tra* transaction)
 {
+	if (createIfNotExistsOnly && !DYN_UTIL_check_unique_name_nothrow(tdbb, transaction, name, obj_trigger))
+		return;
+
 	executeDdlTrigger(tdbb, dsqlScratch, transaction, DTW_BEFORE, DDL_TRIGGER_CREATE_TRIGGER,
 		name, NULL);
 
+	DYN_UTIL_check_unique_name(tdbb, transaction, name, obj_trigger);
+
 	store(tdbb, dsqlScratch, transaction);
 
 	executeDdlTrigger(tdbb, dsqlScratch, transaction, DTW_AFTER, DDL_TRIGGER_CREATE_TRIGGER,
@@ -4010,9 +4021,14 @@ void CreateCollationNode::execute(thread_db* tdbb, DsqlCompilerScratch* dsqlScra
 	// run all statements under savepoint control
 	AutoSavePoint savePoint(tdbb, transaction);
 
+	if (createIfNotExistsOnly && !DYN_UTIL_check_unique_name_nothrow(tdbb, transaction, name, obj_collation))
+		return;
+
 	executeDdlTrigger(tdbb, dsqlScratch, transaction, DTW_BEFORE,
 		DDL_TRIGGER_CREATE_COLLATION, name, NULL);
 
+	DYN_UTIL_check_unique_name(tdbb, transaction, name, obj_collation);
+
 	AutoCacheRequest request(tdbb, drq_s_colls, DYN_REQUESTS);
 
 	STORE(REQUEST_HANDLE request TRANSACTION_HANDLE transaction)
@@ -4400,9 +4416,14 @@ void CreateDomainNode::execute(thread_db* tdbb, DsqlCompilerScratch* dsqlScratch
 	// run all statements under savepoint control
 	AutoSavePoint savePoint(tdbb, transaction);
 
+	if (createIfNotExistsOnly && !DYN_UTIL_check_unique_name_nothrow(tdbb, transaction, nameType->name, obj_field))
+		return;
+
 	executeDdlTrigger(tdbb, dsqlScratch, transaction, DTW_BEFORE,
 		DDL_TRIGGER_CREATE_DOMAIN, nameType->name, NULL);
 
+	DYN_UTIL_check_unique_name(tdbb, transaction, nameType->name, obj_field);
+
 	storeGlobalField(tdbb, transaction, nameType->name, type);
 
 	if (nameType->defaultClause || check || notNull)
@@ -5539,6 +5560,9 @@ void CreateAlterExceptionNode::executeCreate(thread_db* tdbb, DsqlCompilerScratc
 	Attachment* const attachment = transaction->getAttachment();
 	const MetaString& ownerName = attachment->getEffectiveUserName();
 
+	if (createIfNotExistsOnly && !DYN_UTIL_check_unique_name_nothrow(tdbb, transaction, name, obj_exception))
+		return;
+
 	executeDdlTrigger(tdbb, dsqlScratch, transaction, DTW_BEFORE,
 		DDL_TRIGGER_CREATE_EXCEPTION, name, NULL);
 
@@ -5766,9 +5790,14 @@ void CreateAlterSequenceNode::putErrorPrefix(Firebird::Arg::StatusVector& status
 void CreateAlterSequenceNode::executeCreate(thread_db* tdbb, DsqlCompilerScratch* dsqlScratch,
 	jrd_tra* transaction)
 {
+	if (createIfNotExistsOnly && !DYN_UTIL_check_unique_name_nothrow(tdbb, transaction, name, obj_generator))
+		return;
+
 	executeDdlTrigger(tdbb, dsqlScratch, transaction, DTW_BEFORE, DDL_TRIGGER_CREATE_SEQUENCE,
 		name, NULL);
 
+	DYN_UTIL_check_unique_name(tdbb, transaction, name, obj_generator);
+
 	const SINT64 val = value.value_or(1);
 	SLONG initialStep = 1;
 	if (step.has_value())
@@ -5777,6 +5806,7 @@ void CreateAlterSequenceNode::executeCreate(thread_db* tdbb, DsqlCompilerScratch
 		if (initialStep == 0)
 			status_exception::raise(Arg::Gds(isc_dyn_cant_use_zero_increment) << Arg::Str(name));
 	}
+
 	store(tdbb, transaction, name, fb_sysflag_user, val, initialStep);
 
 	executeDdlTrigger(tdbb, dsqlScratch, transaction, DTW_AFTER, DDL_TRIGGER_CREATE_SEQUENCE,
@@ -6398,11 +6428,25 @@ void RelationNode::defineField(thread_db* tdbb, DsqlCompilerScratch* dsqlScratch
 	const ObjectsArray<MetaName>* pkCols)
 {
 	dsql_fld* field = clause->field;
+	dsql_rel* relation = dsqlScratch->relation;
+
+	if (clause->createIfNotExistsOnly)
+	{
+		AutoCacheRequest request(tdbb, drq_l_rel_fld_name, DYN_REQUESTS);
+
+		FOR(REQUEST_HANDLE request TRANSACTION_HANDLE transaction)
+			RFL IN RDB$RELATION_FIELDS
+			WITH RFL.RDB$RELATION_NAME = relation->rel_name.c_str() AND
+				 RFL.RDB$FIELD_NAME = field->fld_name.c_str()
+		{
+			return;
+		}
+		END_FOR
+	}
 
 	// Add the field to the relation being defined for parsing purposes.
 
 	bool permanent = false;
-	dsql_rel* relation = dsqlScratch->relation;
 	if (relation != NULL)
 	{
 		if (!(relation->rel_flags & REL_new_relation))
@@ -6596,12 +6640,26 @@ bool RelationNode::defineDefault(thread_db* /*tdbb*/, DsqlCompilerScratch* dsqlS
 }
 
 // Make a constraint object from a legacy node.
-void RelationNode::makeConstraint(thread_db* /*tdbb*/, DsqlCompilerScratch* dsqlScratch,
+void RelationNode::makeConstraint(thread_db* tdbb, DsqlCompilerScratch* dsqlScratch,
 	jrd_tra* transaction, AddConstraintClause* clause,
 	ObjectsArray<CreateDropConstraint>& constraints, bool* notNull)
 {
 	MemoryPool& pool = dsqlScratch->getPool();
 
+	if (clause->createIfNotExistsOnly)
+	{
+		AutoCacheRequest request(tdbb, drq_l_rel_con, DYN_REQUESTS);
+
+		FOR(REQUEST_HANDLE request TRANSACTION_HANDLE transaction)
+			RC IN RDB$RELATION_CONSTRAINTS
+			WITH RC.RDB$CONSTRAINT_NAME EQ clause->name.c_str() AND
+				 RC.RDB$RELATION_NAME EQ name.c_str()
+		{
+			return;
+		}
+		END_FOR
+	}
+
 	switch (clause->constraintType)
 	{
 		case AddConstraintClause::CTYPE_NOT_NULL:
@@ -7474,6 +7532,9 @@ void CreateRelationNode::checkPermission(thread_db* tdbb, jrd_tra* transaction)
 void CreateRelationNode::execute(thread_db* tdbb, DsqlCompilerScratch* dsqlScratch,
 	jrd_tra* transaction)
 {
+	if (createIfNotExistsOnly && !DYN_UTIL_check_unique_name_nothrow(tdbb, transaction, name, obj_relation))
+		return;
+
 	saveRelation(tdbb, dsqlScratch, name, false, true);
 
 	if (externalFile)
@@ -8790,6 +8851,9 @@ void CreateAlterViewNode::checkPermission(thread_db* tdbb, jrd_tra* transaction)
 void CreateAlterViewNode::execute(thread_db* tdbb, DsqlCompilerScratch* dsqlScratch,
 	jrd_tra* transaction)
 {
+	if (createIfNotExistsOnly && !DYN_UTIL_check_unique_name_nothrow(tdbb, transaction, name, obj_relation))
+		return;
+
 	Attachment* const attachment = transaction->tra_attachment;
 	const MetaString& ownerName = attachment->getEffectiveUserName();
 
@@ -9962,6 +10026,9 @@ void CreateIndexNode::execute(thread_db* tdbb, DsqlCompilerScratch* dsqlScratch,
 	// run all statements under savepoint control
 	AutoSavePoint savePoint(tdbb, transaction);
 
+	if (createIfNotExistsOnly && !DYN_UTIL_check_unique_name_nothrow(tdbb, transaction, name, obj_index))
+		return;
+
 	executeDdlTrigger(tdbb, dsqlScratch, transaction, DTW_BEFORE, DDL_TRIGGER_CREATE_INDEX,
 		name, NULL);
 
@@ -10402,6 +10469,9 @@ void CreateShadowNode::execute(thread_db* tdbb, DsqlCompilerScratch* /*dsqlScrat
 		FIRST 1 X IN RDB$FILES
 		WITH X.RDB$SHADOW_NUMBER EQ number
 	{
+		if (createIfNotExistsOnly)
+			return;
+
 		// msg 165: "Shadow %ld already exists"
 		status_exception::raise(Arg::PrivateDyn(165) << Arg::Num(number));
 	}
@@ -10522,6 +10592,10 @@ void CreateAlterRoleNode::execute(thread_db* tdbb, DsqlCompilerScratch* dsqlScra
 
 	// run all statements under savepoint control
 	AutoSavePoint savePoint(tdbb, transaction);
+	MetaName dummyName;
+
+	if (createIfNotExistsOnly && isItSqlRole(tdbb, transaction, name, dummyName))
+		return;
 
 	executeDdlTrigger(tdbb, dsqlScratch, transaction, DTW_BEFORE,
 		createFlag ? DDL_TRIGGER_CREATE_ROLE : DDL_TRIGGER_ALTER_ROLE, name, NULL);
@@ -10544,7 +10618,6 @@ void CreateAlterRoleNode::execute(thread_db* tdbb, DsqlCompilerScratch* dsqlScra
 		status_exception::raise(Arg::PrivateDyn(193) << name);
 	}
 
-	MetaName dummyName;
 	if (createFlag && isItSqlRole(tdbb, transaction, name, dummyName))
 	{
 		// msg 194: "SQL role @1 already exists"
@@ -10701,6 +10774,8 @@ void MappingNode::runInSecurityDb(SecDbContext* secDbContext)
 	{
 	case MAP_ADD:
 		ddl = "CREATE MAPPING ";
+		if (createIfNotExistsOnly)
+			ddl += "IF NOT EXISTS ";
 		break;
 	case MAP_MOD:
 		ddl = "ALTER MAPPING ";
@@ -11014,6 +11089,8 @@ void MappingNode::execute(thread_db* tdbb, DsqlCompilerScratch* dsqlScratch, jrd
 	case MAP_ADD:
 		if (found)
 		{
+			if (createIfNotExistsOnly)
+				return;
 			(Arg::Gds(isc_map_already_exists) << name).raise();
 		}
 		// fall through ...
@@ -11261,6 +11338,8 @@ void CreateAlterUserNode::execute(thread_db* tdbb, DsqlCompilerScratch* dsqlScra
 			(Arg::Gds(isc_random) << "Missing user name for ALTER CURRENT USER").raise();
 	}
 
+	userData->createIfNotExistsOnly = createIfNotExistsOnly;
+
 	Firebird::LocalStatus s;
 	CheckStatusWrapper statusWrapper(&s);