Resolve conflicts in createas.h/createas.c

createas.h:
Commit e665769 put the check for IF NOT EXISTS clause of CTAS command
into the separate CreateTableAsRelExists(), while 598f4b0 had modified
this file earlier.

createas.c
Commit e665769 used the CreateTableAsRelExists() at the begining of
ExecCreateTableAs(), while GPDB team had cherry-picked more recent
commit 782b169 fixing CREATE OR REPLACE vulnerability. Fix the confict
in a way existing in upstream.

Commit 846005e has modified intorel_shutdown when 598f4b0 has added
the null check in the same place. Keep both variants.

Author: bimboterminator1

src/backend/commands/createas.c

@@ -310,40 +310,10 @@ ExecCreateTableAs(ParseState *pstate, CreateTableAsStmt *stmt,
 
 	Assert(Gp_role != GP_ROLE_EXECUTE);
 
-<<<<<<< HEAD
-	if (stmt->if_not_exists)
-	{
-		Oid			nspid;
-		Oid			oldrelid;
-
-		nspid = RangeVarGetCreationNamespace(into->rel);
-
-		oldrelid = get_relname_relid(into->rel->relname, nspid);
-		if (OidIsValid(oldrelid))
-		{
-			/*
-			 * The relation exists and IF NOT EXISTS has been specified.
-			 *
-			 * If we are in an extension script, insist that the pre-existing
-			 * object be a member of the extension, to avoid security risks.
-			 */
-			ObjectAddressSet(address, RelationRelationId, oldrelid);
-			checkMembershipInCurrentExtension(&address);
-
-			/* OK to skip */
-			ereport(NOTICE,
-					(errcode(ERRCODE_DUPLICATE_TABLE),
-					 errmsg("relation \"%s\" already exists, skipping",
-							into->rel->relname)));
-			return InvalidObjectAddress;
-		}
-	}
-=======
 	/* Check if the relation exists or not */
 	if (CreateTableAsRelExists(stmt))
 		return InvalidObjectAddress;
 
->>>>>>> f315205f3fafd6f6c7c479f480289fcf45700310
 	/*
 	 * Create the tuple receiver object and insert info it will need
 	 */
@@ -537,19 +507,31 @@ bool
 CreateTableAsRelExists(CreateTableAsStmt *ctas)
 {
 	Oid			nspid;
+	Oid			oldrelid;
+	ObjectAddress address;
 	IntoClause *into = ctas->into;
 
 	nspid = RangeVarGetCreationNamespace(into->rel);
 
-	if (get_relname_relid(into->rel->relname, nspid))
+	oldrelid = get_relname_relid(into->rel->relname, nspid);
+	if (OidIsValid(oldrelid))
 	{
 		if (!ctas->if_not_exists)
 			ereport(ERROR,
 					(errcode(ERRCODE_DUPLICATE_TABLE),
 					 errmsg("relation \"%s\" already exists",
 							into->rel->relname)));
 
-		/* The relation exists and IF NOT EXISTS has been specified */
+		/*
+		 * The relation exists and IF NOT EXISTS has been specified.
+		 *
+		 * If we are in an extension script, insist that the pre-existing
+		 * object be a member of the extension, to avoid security risks.
+		 */
+		ObjectAddressSet(address, RelationRelationId, oldrelid);
+		checkMembershipInCurrentExtension(&address);
+
+		/* OK to skip */
 		ereport(NOTICE,
 				(errcode(ERRCODE_DUPLICATE_TABLE),
 				 errmsg("relation \"%s\" already exists, skipping",
@@ -777,14 +759,12 @@ static void
 intorel_shutdown(DestReceiver *self)
 {
 	DR_intorel *myState = (DR_intorel *) self;
-<<<<<<< HEAD
 	Relation	into_rel = myState->rel;
 
 	if (into_rel == NULL)
 		return;
-=======
+
 	IntoClause *into = myState->into;
->>>>>>> f315205f3fafd6f6c7c479f480289fcf45700310
 
 	if (!into->skipData)
 	{

src/include/commands/createas.h

@@ -29,11 +29,8 @@ extern int	GetIntoRelEFlags(IntoClause *intoClause);
 
 extern DestReceiver *CreateIntoRelDestReceiver(IntoClause *intoClause);
 
-<<<<<<< HEAD
 struct QueryDesc;
 extern void intorel_initplan(struct QueryDesc *queryDesc, int eflags);
-=======
 extern bool CreateTableAsRelExists(CreateTableAsStmt *ctas);
->>>>>>> f315205f3fafd6f6c7c479f480289fcf45700310
 
 #endif							/* CREATEAS_H */