diff options
Diffstat (limited to 'src/backend/parser/parser.c')
| -rw-r--r-- | src/backend/parser/parser.c | 74 |
1 files changed, 73 insertions, 1 deletions
diff --git a/src/backend/parser/parser.c b/src/backend/parser/parser.c index 6c331ad338d..de40e64fa8a 100644 --- a/src/backend/parser/parser.c +++ b/src/backend/parser/parser.c @@ -14,7 +14,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/parser/parser.c,v 1.65 2006/03/07 01:00:17 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/parser/parser.c,v 1.66 2006/05/27 17:38:46 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -22,11 +22,15 @@ #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 @@ -40,6 +44,7 @@ raw_parser(const char *str) int yyresult; parsetree = NIL; /* in case grammar forgets to set it */ + have_lookahead = false; scanner_init(str); parser_init(); @@ -53,3 +58,70 @@ raw_parser(const char *str) 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; +} |