Repair bug in regexp split performance improvements.

Commit c8ea87e4b introduced a temporary conversion buffer for
substrings extracted during regexp splits. Unfortunately the code that
sized it was failing to ignore the effects of ignored degenerate
regexp matches, so for regexp_split_* calls it could under-size the
buffer in such cases.

Fix, and add some regression test cases (though those will only catch
the bug if run in a multibyte encoding).

Backpatch to 9.3 as the faulty code was.

Thanks to the PostGIS project, Regina Obe and Paul Ramsey for the
report (via IRC) and assistance in analysis. Patch by me.

diff --git a/src/backend/utils/adt/regexp.c b/src/backend/utils/adt/regexp.c
index 3b7adfb0479df6a4575ac090850b9a84313783d7..92525c2c4de4c2fb463539e554efb91758fcaabf 100644 (file)
--- a/src/backend/utils/adt/regexp.c
+++ b/src/backend/utils/adt/regexp.c
@@ -982,6 +982,7 @@ setup_regexp_matches(text *orig_str, text *pattern, pg_re_flags *re_flags,
    int         array_len;
    int         array_idx;
    int         prev_match_end;
+   int         prev_valid_match_end;
    int         start_search;
    int         maxlen = 0;     /* largest fetch length in characters */
 
@@ -1024,6 +1025,7 @@ setup_regexp_matches(text *orig_str, text *pattern, pg_re_flags *re_flags,
 
    /* search for the pattern, perhaps repeatedly */
    prev_match_end = 0;
+   prev_valid_match_end = 0;
    start_search = 0;
    while (RE_wchar_execute(cpattern, wide_str, wide_len, start_search,
                            pmatch_len, pmatch))
@@ -1076,13 +1078,15 @@ setup_regexp_matches(text *orig_str, text *pattern, pg_re_flags *re_flags,
            matchctx->nmatches++;
 
            /*
-            * check length of unmatched portion between end of previous match
-            * and start of current one
+            * check length of unmatched portion between end of previous valid
+            * (nondegenerate, or degenerate but not ignored) match and start
+            * of current one
             */
            if (fetching_unmatched &&
                pmatch[0].rm_so >= 0 &&
-               (pmatch[0].rm_so - prev_match_end) > maxlen)
-               maxlen = (pmatch[0].rm_so - prev_match_end);
+               (pmatch[0].rm_so - prev_valid_match_end) > maxlen)
+               maxlen = (pmatch[0].rm_so - prev_valid_match_end);
+           prev_valid_match_end = pmatch[0].rm_eo;
        }
        prev_match_end = pmatch[0].rm_eo;
 
@@ -1108,8 +1112,8 @@ setup_regexp_matches(text *orig_str, text *pattern, pg_re_flags *re_flags,
     * input string
     */
    if (fetching_unmatched &&
-       (wide_len - prev_match_end) > maxlen)
-       maxlen = (wide_len - prev_match_end);
+       (wide_len - prev_valid_match_end) > maxlen)
+       maxlen = (wide_len - prev_valid_match_end);
 
    /*
     * Keep a note of the end position of the string for the benefit of

diff --git a/src/test/regress/expected/strings.out b/src/test/regress/expected/strings.out
index 35cadb24aa1f61d91185d0bc9a0eda2ac59d8d4b..3b1a7d80b8269ae0c6f13e39fcbe6dc3cda2db78 100644 (file)
--- a/src/test/regress/expected/strings.out
+++ b/src/test/regress/expected/strings.out
@@ -674,6 +674,24 @@ SELECT regexp_split_to_array('123456','.');
  {"","","","","","",""}
 (1 row)
 
+SELECT regexp_split_to_array('123456','');
+ regexp_split_to_array 
+-----------------------
+ {1,2,3,4,5,6}
+(1 row)
+
+SELECT regexp_split_to_array('123456','(?:)');
+ regexp_split_to_array 
+-----------------------
+ {1,2,3,4,5,6}
+(1 row)
+
+SELECT regexp_split_to_array('1','');
+ regexp_split_to_array 
+-----------------------
+ {1}
+(1 row)
+
 -- errors
 SELECT foo, length(foo) FROM regexp_split_to_table('thE QUick bROWn FOx jUMPs ovEr The lazy dOG', 'e', 'zippy') AS foo;
 ERROR:  invalid regexp option: "z"

diff --git a/src/test/regress/sql/strings.sql b/src/test/regress/sql/strings.sql
index f9cfaeb44ac2f55d8f5c859a0951aaba9e1dd381..5e39458bd2234d5e4b13016115bca137f01831db 100644 (file)
--- a/src/test/regress/sql/strings.sql
+++ b/src/test/regress/sql/strings.sql
@@ -188,6 +188,9 @@ SELECT regexp_split_to_array('the quick brown fox jumps over the lazy dog', 'nom
 SELECT regexp_split_to_array('123456','1');
 SELECT regexp_split_to_array('123456','6');
 SELECT regexp_split_to_array('123456','.');
+SELECT regexp_split_to_array('123456','');
+SELECT regexp_split_to_array('123456','(?:)');
+SELECT regexp_split_to_array('1','');
 -- errors
 SELECT foo, length(foo) FROM regexp_split_to_table('thE QUick bROWn FOx jUMPs ovEr The lazy dOG', 'e', 'zippy') AS foo;
 SELECT regexp_split_to_array('thE QUick bROWn FOx jUMPs ovEr The lazy dOG', 'e', 'iz');