/*------------------------------------------------------------------------- * * parser.c *		Main entry point/driver for PostgreSQL grammar * * Note that the grammar is not allowed to perform any table access * (since we need to be able to do basic parsing even while inside an * aborted transaction).  Therefore, the data structures returned by * the grammar are "raw" parsetrees that still need to be analyzed by * parse_analyze. * * * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION *	  $Header: /cvsroot/pgsql/src/backend/parser/parser.c,v 1.59 2003/08/04 02:40:02 momjian Exp $ * *------------------------------------------------------------------------- */#include "postgres.h"#include "nodes/parsenodes.h"#include "parser/gramparse.h"#include "parser/parse.h"#include "parser/parser.h"#include "parser/parse_expr.h"List	   *parsetree;			/* result of parsing is left here */static int	lookahead_token;	/* one-token lookahead */static bool have_lookahead;		/* lookahead_token set? *//* * raw_parser *		Given a query in string form, do lexical and grammatical analysis. * * Returns a list of raw (un-analyzed) parse trees. */List *raw_parser(const char *str){	int			yyresult;	parsetree = NIL;			/* in case grammar forgets to set it */	have_lookahead = false;	scanner_init(str);	parser_init();	parse_expr_init();	yyresult = yyparse();	scanner_finish();	if (yyresult)				/* error */		return NIL;	return parsetree;}/* * Intermediate filter between parser and base lexer (base_yylex in scan.l). * * The filter is needed because in some cases SQL92 requires more than one * token lookahead.  We reduce these cases to one-token lookahead by combining * tokens here, in order to keep the grammar LR(1). * * Using a filter is simpler than trying to recognize multiword tokens * directly in scan.l, because we'd have to allow for comments between the * words ... */intyylex(void){	int			cur_token;	/* Get next token --- we might already have it */	if (have_lookahead)	{		cur_token = lookahead_token;		have_lookahead = false;	}	else		cur_token = base_yylex();	/* Do we need to look ahead for a possible multiword token? */	switch (cur_token)	{		case UNION:			/* UNION JOIN must be reduced to a single UNIONJOIN token */			lookahead_token = base_yylex();			if (lookahead_token == JOIN)				cur_token = UNIONJOIN;			else				have_lookahead = true;			break;		default:			break;	}	return cur_token;}