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109 lines
2.5 KiB
C
109 lines
2.5 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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* parse_analyze.
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*
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*
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* Portions Copyright (c) 1996-2002, 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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* $Header: /cvsroot/pgsql/src/backend/parser/parser.c,v 1.58 2003/05/05 01:59:02 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "nodes/parsenodes.h"
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#include "parser/gramparse.h"
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#include "parser/parse.h"
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#include "parser/parser.h"
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#include "parser/parse_expr.h"
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List *parsetree; /* result of parsing is left here */
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static int lookahead_token; /* one-token lookahead */
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static bool have_lookahead; /* lookahead_token set? */
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/*
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* raw_parser
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* Given a query in string form, do lexical and grammatical analysis.
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*
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* Returns a list of raw (un-analyzed) parse trees.
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*/
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List *
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raw_parser(const char *str)
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{
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int yyresult;
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parsetree = NIL; /* in case grammar forgets to set it */
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have_lookahead = false;
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scanner_init(str);
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parser_init();
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parse_expr_init();
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yyresult = yyparse();
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scanner_finish();
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if (yyresult) /* error */
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return NIL;
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return parsetree;
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}
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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 SQL92 requires more than one
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* token lookahead. We reduce these cases to one-token lookahead by combining
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* tokens here, in order to keep the grammar LR(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 ...
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*/
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int
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yylex(void)
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{
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int cur_token;
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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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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 UNION:
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/* UNION JOIN must be reduced to a single UNIONJOIN token */
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lookahead_token = base_yylex();
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if (lookahead_token == JOIN)
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cur_token = UNIONJOIN;
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else
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have_lookahead = true;
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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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