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Implement regexp_match(), a simplified alternative to regexp_matches().

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regexp_match() is like regexp_matches(), but it disallows the 'g' flag
and in consequence does not need to return a set.  Instead, it returns
a simple text array value, or NULL if there's no match.  Previously people
usually got that behavior with a sub-select, but this way is considerably
more efficient.

Documentation adjusted so that regexp_match() is presented first and then
regexp_matches() is introduced as a more complicated version.  This is
a bit historically revisionist but seems pedagogically better.

Still TODO: extend contrib/citext to support this function.

Emre Hasegeli, reviewed by David Johnston

Discussion: <CAE2gYzy42sna2ME_e3y1KLQ-4UBrB-eVF0SWn8QG39sQSeVhEw@mail.gmail.com>
This commit is contained in:
Tom Lane
2016-08-17 18:32:56 -04:00
parent 2d7e591007
commit cf9b0fea5f
9 changed files with 253 additions and 94 deletions
Download Patch File Download Diff File Expand all files Collapse all files

137
src/backend/utils/adt/regexp.c
View File

@@ -47,7 +47,7 @@ typedef struct pg_re_flags
bool glob; /* do it globally (for each occurrence) */
} pg_re_flags;
/* cross-call state for regexp_matches(), also regexp_split() */
/* cross-call state for regexp_match and regexp_split functions */
typedef struct regexp_matches_ctx
{
text *orig_str; /* data string in original TEXT form */
@@ -57,7 +57,7 @@ typedef struct regexp_matches_ctx
/* so the number of entries in match_locs is nmatches * npatterns * 2 */
int *match_locs; /* 0-based character indexes */
int next_match; /* 0-based index of next match to process */
/* workspace for build_regexp_matches_result() */
/* workspace for build_regexp_match_result() */
Datum *elems; /* has npatterns elements */
bool *nulls; /* has npatterns elements */
} regexp_matches_ctx;
@@ -107,13 +107,12 @@ static cached_re_str re_array[MAX_CACHED_RES]; /* cached re's */
/* Local functions */
static regexp_matches_ctx *setup_regexp_matches(text *orig_str, text *pattern,
text *flags,
pg_re_flags *flags,
Oid collation,
bool force_glob,
bool use_subpatterns,
bool ignore_degenerate);
static void cleanup_regexp_matches(regexp_matches_ctx *matchctx);
static ArrayType *build_regexp_matches_result(regexp_matches_ctx *matchctx);
static ArrayType *build_regexp_match_result(regexp_matches_ctx *matchctx);
static Datum build_regexp_split_result(regexp_matches_ctx *splitctx);
@@ -350,7 +349,7 @@ RE_compile_and_execute(text *text_re, char *dat, int dat_len,
/*
* parse_re_flags - parse the options argument of regexp_matches and friends
* parse_re_flags - parse the options argument of regexp_match and friends
*
* flags --- output argument, filled with desired options
* opts --- TEXT object, or NULL for defaults
@@ -840,9 +839,53 @@ similar_escape(PG_FUNCTION_ARGS)
PG_RETURN_TEXT_P(result);
}
/*
* regexp_match()
* Return the first substring(s) matching a pattern within a string.
*/
Datum
regexp_match(PG_FUNCTION_ARGS)
{
text *orig_str = PG_GETARG_TEXT_PP(0);
text *pattern = PG_GETARG_TEXT_PP(1);
text *flags = PG_GETARG_TEXT_PP_IF_EXISTS(2);
pg_re_flags re_flags;
regexp_matches_ctx *matchctx;
/* Determine options */
parse_re_flags(&re_flags, flags);
/* User mustn't specify 'g' */
if (re_flags.glob)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("regexp_match does not support the global option"),
errhint("Use the regexp_matches function instead.")));
matchctx = setup_regexp_matches(orig_str, pattern, &re_flags,
PG_GET_COLLATION(), true, false);
if (matchctx->nmatches == 0)
PG_RETURN_NULL();
Assert(matchctx->nmatches == 1);
/* Create workspace that build_regexp_match_result needs */
matchctx->elems = (Datum *) palloc(sizeof(Datum) * matchctx->npatterns);
matchctx->nulls = (bool *) palloc(sizeof(bool) * matchctx->npatterns);
PG_RETURN_DATUM(PointerGetDatum(build_regexp_match_result(matchctx)));
}
/* This is separate to keep the opr_sanity regression test from complaining */
Datum
regexp_match_no_flags(PG_FUNCTION_ARGS)
{
return regexp_match(fcinfo);
}
/*
* regexp_matches()
* Return a table of matches of a pattern within a string.
* Return a table of all matches of a pattern within a string.
*/
Datum
regexp_matches(PG_FUNCTION_ARGS)
@@ -854,18 +897,22 @@ regexp_matches(PG_FUNCTION_ARGS)
{
text *pattern = PG_GETARG_TEXT_PP(1);
text *flags = PG_GETARG_TEXT_PP_IF_EXISTS(2);
pg_re_flags re_flags;
MemoryContext oldcontext;
funcctx = SRF_FIRSTCALL_INIT();
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
/* Determine options */
parse_re_flags(&re_flags, flags);
/* be sure to copy the input string into the multi-call ctx */
matchctx = setup_regexp_matches(PG_GETARG_TEXT_P_COPY(0), pattern,
flags,
&re_flags,
PG_GET_COLLATION(),
false, true, false);
true, false);
/* Pre-create workspace that build_regexp_matches_result needs */
/* Pre-create workspace that build_regexp_match_result needs */
matchctx->elems = (Datum *) palloc(sizeof(Datum) * matchctx->npatterns);
matchctx->nulls = (bool *) palloc(sizeof(bool) * matchctx->npatterns);
@@ -880,7 +927,7 @@ regexp_matches(PG_FUNCTION_ARGS)
{
ArrayType *result_ary;
result_ary = build_regexp_matches_result(matchctx);
result_ary = build_regexp_match_result(matchctx);
matchctx->next_match++;
SRF_RETURN_NEXT(funcctx, PointerGetDatum(result_ary));
}
@@ -899,28 +946,27 @@ regexp_matches_no_flags(PG_FUNCTION_ARGS)
}
/*
* setup_regexp_matches --- do the initial matching for regexp_matches()
* or regexp_split()
* setup_regexp_matches --- do the initial matching for regexp_match
* and regexp_split functions
*
* To avoid having to re-find the compiled pattern on each call, we do
* all the matching in one swoop. The returned regexp_matches_ctx contains
* the locations of all the substrings matching the pattern.
*
* The three bool parameters have only two patterns (one for each caller)
* but it seems clearer to distinguish the functionality this way than to
* key it all off one "is_split" flag.
* The two bool parameters have only two patterns (one for matching, one for
* splitting) but it seems clearer to distinguish the functionality this way
* than to key it all off one "is_split" flag.
*/
static regexp_matches_ctx *
setup_regexp_matches(text *orig_str, text *pattern, text *flags,
setup_regexp_matches(text *orig_str, text *pattern, pg_re_flags *re_flags,
Oid collation,
bool force_glob, bool use_subpatterns,
bool use_subpatterns,
bool ignore_degenerate)
{
regexp_matches_ctx *matchctx = palloc0(sizeof(regexp_matches_ctx));
int orig_len;
pg_wchar *wide_str;
int wide_len;
pg_re_flags re_flags;
regex_t *cpattern;
regmatch_t *pmatch;
int pmatch_len;
@@ -937,21 +983,8 @@ setup_regexp_matches(text *orig_str, text *pattern, text *flags,
wide_str = (pg_wchar *) palloc(sizeof(pg_wchar) * (orig_len + 1));
wide_len = pg_mb2wchar_with_len(VARDATA_ANY(orig_str), wide_str, orig_len);
/* determine options */
parse_re_flags(&re_flags, flags);
if (force_glob)
{
/* user mustn't specify 'g' for regexp_split */
if (re_flags.glob)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("regexp_split does not support the global option")));
/* but we find all the matches anyway */
re_flags.glob = true;
}
/* set up the compiled pattern */
cpattern = RE_compile_and_cache(pattern, re_flags.cflags, collation);
cpattern = RE_compile_and_cache(pattern, re_flags->cflags, collation);
/* do we want to remember subpatterns? */
if (use_subpatterns && cpattern->re_nsub > 0)
@@ -970,7 +1003,7 @@ setup_regexp_matches(text *orig_str, text *pattern, text *flags,
pmatch = palloc(sizeof(regmatch_t) * pmatch_len);
/* the real output space (grown dynamically if needed) */
array_len = re_flags.glob ? 256 : 32;
array_len = re_flags->glob ? 256 : 32;
matchctx->match_locs = (int *) palloc(sizeof(int) * array_len);
array_idx = 0;
@@ -1018,7 +1051,7 @@ setup_regexp_matches(text *orig_str, text *pattern, text *flags,
prev_match_end = pmatch[0].rm_eo;
/* if not glob, stop after one match */
if (!re_flags.glob)
if (!re_flags->glob)
break;
/*
@@ -1057,10 +1090,10 @@ cleanup_regexp_matches(regexp_matches_ctx *matchctx)
}
/*
* build_regexp_matches_result - build output array for current match
* build_regexp_match_result - build output array for current match
*/
static ArrayType *
build_regexp_matches_result(regexp_matches_ctx *matchctx)
build_regexp_match_result(regexp_matches_ctx *matchctx)
{
Datum *elems = matchctx->elems;
bool *nulls = matchctx->nulls;
@@ -1114,16 +1147,27 @@ regexp_split_to_table(PG_FUNCTION_ARGS)
{
text *pattern = PG_GETARG_TEXT_PP(1);
text *flags = PG_GETARG_TEXT_PP_IF_EXISTS(2);
pg_re_flags re_flags;
MemoryContext oldcontext;
funcctx = SRF_FIRSTCALL_INIT();
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
/* Determine options */
parse_re_flags(&re_flags, flags);
/* User mustn't specify 'g' */
if (re_flags.glob)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("regexp_split_to_table does not support the global option")));
/* But we find all the matches anyway */
re_flags.glob = true;
/* be sure to copy the input string into the multi-call ctx */
splitctx = setup_regexp_matches(PG_GETARG_TEXT_P_COPY(0), pattern,
flags,
&re_flags,
PG_GET_COLLATION(),
true, false, true);
false, true);
MemoryContextSwitchTo(oldcontext);
funcctx->user_fctx = (void *) splitctx;
@@ -1162,13 +1206,24 @@ Datum
regexp_split_to_array(PG_FUNCTION_ARGS)
{
ArrayBuildState *astate = NULL;
pg_re_flags re_flags;
regexp_matches_ctx *splitctx;
/* Determine options */
parse_re_flags(&re_flags, PG_GETARG_TEXT_PP_IF_EXISTS(2));
/* User mustn't specify 'g' */
if (re_flags.glob)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("regexp_split_to_array does not support the global option")));
/* But we find all the matches anyway */
re_flags.glob = true;
splitctx = setup_regexp_matches(PG_GETARG_TEXT_PP(0),
PG_GETARG_TEXT_PP(1),
PG_GETARG_TEXT_PP_IF_EXISTS(2),
&re_flags,
PG_GET_COLLATION(),
true, false, true);
false, true);
while (splitctx->next_match <= splitctx->nmatches)
{