postgres创建表的过程以及部分源码分析

typedef struct CreateStmt
{
	NodeTag		type;
	RangeVar   *relation;		/* relation to create */
	List	   *tableElts;		/* column definitions (list of ColumnDef) */
	List	   *inhRelations;	/* relations to inherit from (list of
								 * inhRelation) */
	TypeName   *ofTypename;		/* OF typename */
	List	   *constraints;	/* constraints (list of Constraint nodes) */
	List	   *options;		/* options from WITH clause */
	OnCommitAction oncommit;	/* what do we do at COMMIT? */
	char	   *tablespacename; /* table space to use, or NULL */
	bool		if_not_exists;	/* just do nothing if it already exists? */
} CreateStmt;

char *
deparse_query_def(Query *query)
{
	StringInfoData buf;

	initStringInfo(&buf);
	get_query_def(query, &buf, NIL, NULL,
			PRETTYFLAG_INDENT, WRAP_COLUMN_DEFAULT, 0);

	return buf.data;
}

Datum
current_user(PG_FUNCTION_ARGS)
{
	PG_RETURN_DATUM(DirectFunctionCall1(namein, CStringGetDatum(GetUserNameFromId(GetUserId()))));
}

postgres=# select CURRENT_USER;
 current_user 
--------------
 postgres
(1 row)