8ecd535169
Also, since WITH is now a reserved word, simplify the token merging code to only deal with WITH_TIME. by Tom Lane and myself
130 lines
3.4 KiB
C
130 lines
3.4 KiB
C
/*-------------------------------------------------------------------------
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*
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* parser.c
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* Main entry point/driver for PostgreSQL grammar
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*
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* Note that the grammar is not allowed to perform any table access
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* (since we need to be able to do basic parsing even while inside an
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* aborted transaction). Therefore, the data structures returned by
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* the grammar are "raw" parsetrees that still need to be analyzed by
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* analyze.c and related files.
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*
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*
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* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/interfaces/ecpg/preproc/parser.c,v 1.4 2008/10/28 14:09:45 petere Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres_fe.h"
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#include "extern.h"
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#include "preproc.h"
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static bool have_lookahead; /* is lookahead info valid? */
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static int lookahead_token; /* one-token lookahead */
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static YYSTYPE lookahead_yylval; /* yylval for lookahead token */
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static YYLTYPE lookahead_yylloc; /* yylloc for lookahead token */
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/*
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* Intermediate filter between parser and base lexer (base_yylex in scan.l).
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*
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* The filter is needed because in some cases the standard SQL grammar
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* requires more than one token lookahead. We reduce these cases to one-token
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* lookahead by combining tokens here, in order to keep the grammar LALR(1).
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*
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* Using a filter is simpler than trying to recognize multiword tokens
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* directly in scan.l, because we'd have to allow for comments between the
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* words. Furthermore it's not clear how to do it without re-introducing
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* scanner backtrack, which would cost more performance than this filter
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* layer does.
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*/
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int
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filtered_base_yylex(void)
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{
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int cur_token;
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int next_token;
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YYSTYPE cur_yylval;
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YYLTYPE cur_yylloc;
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/* Get next token --- we might already have it */
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if (have_lookahead)
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{
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cur_token = lookahead_token;
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base_yylval = lookahead_yylval;
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base_yylloc = lookahead_yylloc;
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have_lookahead = false;
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}
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else
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cur_token = base_yylex();
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/* Do we need to look ahead for a possible multiword token? */
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switch (cur_token)
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{
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case NULLS_P:
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/*
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* NULLS FIRST and NULLS LAST must be reduced to one token
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*/
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cur_yylval = base_yylval;
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cur_yylloc = base_yylloc;
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next_token = base_yylex();
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switch (next_token)
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{
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case FIRST_P:
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cur_token = NULLS_FIRST;
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break;
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case LAST_P:
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cur_token = NULLS_LAST;
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break;
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default:
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/* save the lookahead token for next time */
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lookahead_token = next_token;
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lookahead_yylval = base_yylval;
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lookahead_yylloc = base_yylloc;
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have_lookahead = true;
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/* and back up the output info to cur_token */
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base_yylval = cur_yylval;
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base_yylloc = cur_yylloc;
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break;
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}
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break;
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case WITH:
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/*
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* WITH TIME must be reduced to one token
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*/
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cur_yylval = base_yylval;
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cur_yylloc = base_yylloc;
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next_token = base_yylex();
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switch (next_token)
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{
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case TIME:
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cur_token = WITH_TIME;
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break;
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default:
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/* save the lookahead token for next time */
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lookahead_token = next_token;
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lookahead_yylval = base_yylval;
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lookahead_yylloc = base_yylloc;
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have_lookahead = true;
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/* and back up the output info to cur_token */
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base_yylval = cur_yylval;
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base_yylloc = cur_yylloc;
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break;
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}
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break;
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default:
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break;
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}
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return cur_token;
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}
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