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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
* analyze.c and related files.
*
*
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/parser/parser.c,v 1.66 2006/05/27 17:38:46 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "parser/gramparse.h"
#include "parser/parse.h"
#include "parser/parser.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();
yyresult = base_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 the standard SQL grammar
* requires more than one token lookahead. We reduce these cases to one-token
* lookahead by combining tokens here, in order to keep the grammar LALR(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. Furthermore it's not clear how to do it without re-introducing
* scanner backtrack, which would cost more performance than this filter
* layer does.
*/
int
filtered_base_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 WITH:
/*
* WITH CASCADED, LOCAL, or CHECK must be reduced to one token
*
* XXX an alternative way is to recognize just WITH_TIME and
* put the ugliness into the datetime datatype productions
* instead of WITH CHECK OPTION. However that requires promoting
* WITH to a fully reserved word. If we ever have to do that
* anyway (perhaps for SQL99 recursive queries), come back and
* simplify this code.
*/
lookahead_token = base_yylex();
switch (lookahead_token)
{
case CASCADED:
cur_token = WITH_CASCADED;
break;
case LOCAL:
cur_token = WITH_LOCAL;
break;
case CHECK:
cur_token = WITH_CHECK;
break;
default:
have_lookahead = true;
break;
}
break;
default:
break;
}
return cur_token;
}
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