Function ExecCreateTableAs

src/backend/commands/createas.c:326–595

* ExecCreateTableAs -- execute a CREATE TABLE AS command */

 * ExecCreateTableAs -- execute a CREATE TABLE AS command
 */
ObjectAddress
ExecCreateTableAs(ParseState *pstate, CreateTableAsStmt *stmt,
				  ParamListInfo params, QueryEnvironment *queryEnv,
				  QueryCompletion *qc)
{
	Query	   *query = castNode(Query, stmt->query);
	IntoClause *into = stmt->into;
	bool		is_matview = (into->viewQuery != NULL);
	DestReceiver *dest;
	Oid			save_userid = InvalidOid;
	int			save_sec_context = 0;
	int			save_nestlevel = 0;
	ObjectAddress address;
	List	   *rewritten;
	PlannedStmt *plan;
	QueryDesc  *queryDesc;
	Query	   *query_immv = NULL;
	Oid         relationOid = InvalidOid;   /* relation that is modified */
	AutoStatsCmdType cmdType = AUTOSTATS_CMDTYPE_SENTINEL;  /* command type */

	Assert(Gp_role != GP_ROLE_EXECUTE);

	/* Check if the relation exists or not */
	{
		Oid			nspid;
		Oid			oldrelid;

		nspid = RangeVarGetCreationNamespace(into->rel);

		oldrelid = get_relname_relid(into->rel->relname, nspid);
		if (OidIsValid(oldrelid))
		{
			if (!stmt->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.
			 *
			 * 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;
		}
	}

	/*
	 * Create the tuple receiver object and insert info it will need