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/*-------------------------------------------------------------------------
*
* 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) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/parser/parser.c,v 1.48 2001/01/24 19:43:03 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"
#if defined(FLEX_SCANNER)
extern void DeleteBuffer(void);
#endif /* FLEX_SCANNER */
char *parseString; /* the char* which holds the string to be
* parsed */
List *parsetree; /* result of parsing is left here */
static int lookahead_token; /* one-token lookahead */
static bool have_lookahead; /* lookahead_token set? */
/*
* parser
* Given a query in string form, and optionally info about
* parameter types, do lexical and syntactic analysis.
*
* Returns a list of raw (un-analyzed) parse trees.
*/
List *
parser(char *str, Oid *typev, int nargs)
{
int yyresult;
parseString = str;
parsetree = NIL; /* in case parser forgets to set it */
have_lookahead = false;
scanner_init();
parser_init(typev, nargs);
parse_expr_init();
yyresult = yyparse();
#if defined(FLEX_SCANNER)
DeleteBuffer();
#endif /* FLEX_SCANNER */
clearerr(stdin);
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 ...
*/
int
yylex(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;
}
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