From: Tom Lane Date: Sat, 1 Mar 2014 20:21:11 +0000 (-0500) Subject: Allow regex operations to be terminated early by query cancel requests. X-Git-Tag: REL9_0_17~15 X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=43af0e8c6c1a455d038730f3ec33a5f23a560fe2;p=postgresql Allow regex operations to be terminated early by query cancel requests. The regex code didn't have any provision for query cancel; which is unsurprising given its non-Postgres origin, but still problematic since some operations can take a long time. Introduce a callback function to check for a pending query cancel or session termination request, and call it in a couple of strategic spots where we can make the regex code exit with an error indicator. If we ever actually split out the regex code as a standalone library, some additional work will be needed to let the cancel callback function be specified externally to the library. But that's straightforward (certainly so by comparison to putting the locale-dependent character classification logic on a similar arms-length basis), and there seems no need to do it right now. A bigger issue is that there may be more places than these two where we need to check for cancels. We can always add more checks later, now that the infrastructure is in place. Since there are known examples of not-terribly-long regexes that can lock up a backend for a long time, back-patch to all supported branches. I have hopes of fixing the known performance problems later, but adding query cancel ability seems like a good idea even if they were all fixed. --- diff --git a/src/backend/regex/regc_nfa.c b/src/backend/regex/regc_nfa.c index c99a1f13d6..e0e32344ca 100644 --- a/src/backend/regex/regc_nfa.c +++ b/src/backend/regex/regc_nfa.c @@ -174,11 +174,23 @@ newstate(struct nfa * nfa) { struct state *s; + /* + * This is a handy place to check for operation cancel during regex + * compilation, since no code path will go very long without making a new + * state. + */ + if (CANCEL_REQUESTED(nfa->v->re)) + { + NERR(REG_CANCEL); + return NULL; + } + if (TooManyStates(nfa)) { NERR(REG_ETOOBIG); return NULL; } + if (nfa->free != NULL) { s = nfa->free; diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c index e5e5ee86bf..e121fd9a85 100644 --- a/src/backend/regex/regcomp.c +++ b/src/backend/regex/regcomp.c @@ -34,6 +34,8 @@ #include "regex/regguts.h" +#include "miscadmin.h" /* needed by rcancelrequested() */ + /* * forward declarations, up here so forward datatypes etc. are defined early */ @@ -67,6 +69,7 @@ static long nfanode(struct vars *, struct subre *, FILE *); static int newlacon(struct vars *, struct state *, struct state *, int); static void freelacons(struct subre *, int); static void rfree(regex_t *); +static int rcancelrequested(void); #ifdef REG_DEBUG static void dump(regex_t *, FILE *); @@ -274,6 +277,7 @@ struct vars /* static function list */ static struct fns functions = { rfree, /* regfree insides */ + rcancelrequested /* check for cancel request */ }; @@ -1869,6 +1873,22 @@ rfree(regex_t *re) } } +/* + * rcancelrequested - check for external request to cancel regex operation + * + * Return nonzero to fail the operation with error code REG_CANCEL, + * zero to keep going + * + * The current implementation is Postgres-specific. If we ever get around + * to splitting the regex code out as a standalone library, there will need + * to be some API to let applications define a callback function for this. + */ +static int +rcancelrequested(void) +{ + return InterruptPending && (QueryCancelPending || ProcDiePending); +} + #ifdef REG_DEBUG /* diff --git a/src/backend/regex/regexec.c b/src/backend/regex/regexec.c index 16cdd89757..59a7da49b9 100644 --- a/src/backend/regex/regexec.c +++ b/src/backend/regex/regexec.c @@ -710,6 +710,10 @@ cdissect(struct vars * v, assert(t != NULL); MDEBUG(("cdissect %ld-%ld %c\n", LOFF(begin), LOFF(end), t->op)); + /* handy place to check for operation cancel */ + if (CANCEL_REQUESTED(v->re)) + return REG_CANCEL; + switch (t->op) { case '=': /* terminal node */ diff --git a/src/backend/utils/adt/regexp.c b/src/backend/utils/adt/regexp.c index ef17ebb169..8b48d34fdb 100644 --- a/src/backend/utils/adt/regexp.c +++ b/src/backend/utils/adt/regexp.c @@ -31,6 +31,7 @@ #include "catalog/pg_type.h" #include "funcapi.h" +#include "miscadmin.h" #include "regex/regex.h" #include "utils/builtins.h" #include "utils/guc.h" @@ -183,6 +184,15 @@ RE_compile_and_cache(text *text_re, int cflags) if (regcomp_result != REG_OKAY) { /* re didn't compile (no need for pg_regfree, if so) */ + + /* + * Here and in other places in this file, do CHECK_FOR_INTERRUPTS + * before reporting a regex error. This is so that if the regex + * library aborts and returns REG_CANCEL, we don't print an error + * message that implies the regex was invalid. + */ + CHECK_FOR_INTERRUPTS(); + pg_regerror(regcomp_result, &re_temp.cre_re, errMsg, sizeof(errMsg)); ereport(ERROR, (errcode(ERRCODE_INVALID_REGULAR_EXPRESSION), @@ -262,6 +272,7 @@ RE_wchar_execute(regex_t *re, pg_wchar *data, int data_len, if (regexec_result != REG_OKAY && regexec_result != REG_NOMATCH) { /* re failed??? */ + CHECK_FOR_INTERRUPTS(); pg_regerror(regexec_result, re, errMsg, sizeof(errMsg)); ereport(ERROR, (errcode(ERRCODE_INVALID_REGULAR_EXPRESSION), @@ -1194,6 +1205,7 @@ regexp_fixed_prefix(text *text_re, bool case_insensitive, default: /* re failed??? */ + CHECK_FOR_INTERRUPTS(); pg_regerror(re_result, re, errMsg, sizeof(errMsg)); ereport(ERROR, (errcode(ERRCODE_INVALID_REGULAR_EXPRESSION), diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c index f64d461698..f14a9bd3fb 100644 --- a/src/backend/utils/adt/varlena.c +++ b/src/backend/utils/adt/varlena.c @@ -2785,6 +2785,7 @@ replace_text_regexp(text *src_text, void *regexp, { char errMsg[100]; + CHECK_FOR_INTERRUPTS(); pg_regerror(regexec_result, re, errMsg, sizeof(errMsg)); ereport(ERROR, (errcode(ERRCODE_INVALID_REGULAR_EXPRESSION), diff --git a/src/include/regex/regerrs.h b/src/include/regex/regerrs.h index 15da324b66..956b56b50e 100644 --- a/src/include/regex/regerrs.h +++ b/src/include/regex/regerrs.h @@ -81,3 +81,7 @@ { REG_ECOLORS, "REG_ECOLORS", "too many colors" }, + +{ + REG_CANCEL, "REG_CANCEL", "operation cancelled" +}, diff --git a/src/include/regex/regex.h b/src/include/regex/regex.h index adaf1a168d..0680d4bcfd 100644 --- a/src/include/regex/regex.h +++ b/src/include/regex/regex.h @@ -153,6 +153,7 @@ typedef struct #define REG_BADOPT 18 /* invalid embedded option */ #define REG_ETOOBIG 19 /* nfa has too many states */ #define REG_ECOLORS 20 /* too many colors */ +#define REG_CANCEL 21 /* operation cancelled */ /* two specials for debugging and testing */ #define REG_ATOI 101 /* convert error-code name to number */ #define REG_ITOA 102 /* convert error-code number to name */ diff --git a/src/include/regex/regguts.h b/src/include/regex/regguts.h index 9cd0ef9fdf..1a0a8bd7cd 100644 --- a/src/include/regex/regguts.h +++ b/src/include/regex/regguts.h @@ -403,8 +403,11 @@ struct subre struct fns { void FUNCPTR(free, (regex_t *)); + int FUNCPTR(cancel_requested, (void)); }; +#define CANCEL_REQUESTED(re) \ + ((*((struct fns *) (re)->re_fns)->cancel_requested) ()) /*