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

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

View File

@@ -628,6 +628,8 @@ extern Datum textregexsubstr(PG_FUNCTION_ARGS);
extern Datum textregexreplace_noopt(PG_FUNCTION_ARGS);
extern Datum textregexreplace(PG_FUNCTION_ARGS);
extern Datum similar_escape(PG_FUNCTION_ARGS);
extern Datum regexp_match(PG_FUNCTION_ARGS);
extern Datum regexp_match_no_flags(PG_FUNCTION_ARGS);
extern Datum regexp_matches(PG_FUNCTION_ARGS);
extern Datum regexp_matches_no_flags(PG_FUNCTION_ARGS);
extern Datum regexp_split_to_table(PG_FUNCTION_ARGS);