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Add assorted new regexp_xxx SQL functions.

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This patch adds new functions regexp_count(), regexp_instr(),
regexp_like(), and regexp_substr(), and extends regexp_replace()
with some new optional arguments.  All these functions follow
the definitions used in Oracle, although there are small differences
in the regexp language due to using our own regexp engine -- most
notably, that the default newline-matching behavior is different.
Similar functions appear in DB2 and elsewhere, too.  Aside from
easing portability, these functions are easier to use for certain
tasks than our existing regexp_match[es] functions.

Gilles Darold, heavily revised by me

Discussion: https://postgr.es/m/fc160ee0-c843-b024-29bb-97b5da61971f@darold.net
This commit is contained in:
Tom Lane
2021-08-03 13:08:49 -04:00
parent 9e51cc87fd
commit 6424337073
8 changed files with 1340 additions and 47 deletions
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33
src/backend/utils/adt/varlena.c
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@@ -4496,23 +4496,28 @@ appendStringInfoRegexpSubstr(StringInfo str, text *replace_text,
/*
* replace_text_regexp
*
* replace text that matches to regexp in src_text to replace_text.
* replace substring(s) in src_text that match regexp with replace_text.
*
* search_start: the character (not byte) offset in src_text at which to
* begin searching.
* n: if 0, replace all matches; if > 0, replace only the N'th match.
*
* Note: to avoid having to include regex.h in builtins.h, we declare
* the regexp argument as void *, but really it's regex_t *.
*/
text *
replace_text_regexp(text *src_text, void *regexp,
text *replace_text, bool glob)
text *replace_text,
int search_start, int n)
{
text *ret_text;
regex_t *re = (regex_t *) regexp;
int src_text_len = VARSIZE_ANY_EXHDR(src_text);
int nmatches = 0;
StringInfoData buf;
regmatch_t pmatch[REGEXP_REPLACE_BACKREF_CNT];
pg_wchar *data;
size_t data_len;
int search_start;
int data_pos;
char *start_ptr;
bool have_escape;
@@ -4530,7 +4535,6 @@ replace_text_regexp(text *src_text, void *regexp,
start_ptr = (char *) VARDATA_ANY(src_text);
data_pos = 0;
search_start = 0;
while (search_start <= data_len)
{
int regexec_result;
@@ -4560,6 +4564,23 @@ replace_text_regexp(text *src_text, void *regexp,
errmsg("regular expression failed: %s", errMsg)));
}
/*
* Count matches, and decide whether to replace this match.
*/
nmatches++;
if (n > 0 && nmatches != n)
{
/*
* No, so advance search_start, but not start_ptr/data_pos. (Thus,
* we treat the matched text as if it weren't matched, and copy it
* to the output later.)
*/
search_start = pmatch[0].rm_eo;
if (pmatch[0].rm_so == pmatch[0].rm_eo)
search_start++;
continue;
}
/*
* Copy the text to the left of the match position. Note we are given
* character not byte indexes.
@@ -4596,9 +4617,9 @@ replace_text_regexp(text *src_text, void *regexp,
data_pos = pmatch[0].rm_eo;
/*
* When global option is off, replace the first instance only.
* If we only want to replace one occurrence, we're done.
*/
if (!glob)
if (n > 0)
break;
/*