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-rw-r--r--src/backend/regex/regcomp.c22
-rw-r--r--src/test/modules/test_regex/expected/test_regex.out22
-rw-r--r--src/test/modules/test_regex/sql/test_regex.sql6
-rw-r--r--src/test/regress/expected/regex.out19
-rw-r--r--src/test/regress/sql/regex.sql5
5 files changed, 69 insertions, 5 deletions
diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c
index 60a220c57ab..bfe12eb08b3 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -1086,11 +1086,23 @@ parseqatom(struct vars *v,
/* annoying special case: {0} or {0,0} cancels everything */
if (m == 0 && n == 0)
{
- if (atom != NULL)
- freesubre(v, atom);
- if (atomtype == '(')
- v->subs[subno] = NULL;
- delsub(v->nfa, lp, rp);
+ /*
+ * If we had capturing subexpression(s) within the atom, we don't want
+ * to destroy them, because it's legal (if useless) to back-ref them
+ * later. Hence, just unlink the atom from lp/rp and then ignore it.
+ */
+ if (atom != NULL && (atom->flags & CAP))
+ {
+ delsub(v->nfa, lp, atom->begin);
+ delsub(v->nfa, atom->end, rp);
+ }
+ else
+ {
+ /* Otherwise, we can clean up any subre infrastructure we made */
+ if (atom != NULL)
+ freesubre(v, atom);
+ delsub(v->nfa, lp, rp);
+ }
EMPTYARC(lp, rp);
return top;
}
diff --git a/src/test/modules/test_regex/expected/test_regex.out b/src/test/modules/test_regex/expected/test_regex.out
index 83fb9a8b9ca..06f8881cfaf 100644
--- a/src/test/modules/test_regex/expected/test_regex.out
+++ b/src/test/modules/test_regex/expected/test_regex.out
@@ -3490,6 +3490,28 @@ select * from test_regex('((.))(\2){0}', 'xy', 'RPQ');
{x,x,x,NULL}
(2 rows)
+-- expectNomatch 21.39 PQR {(.){0}(\1)} xxx
+select * from test_regex('(.){0}(\1)', 'xxx', 'PQR');
+ test_regex
+--------------------------------------------
+ {2,REG_UBACKREF,REG_UBOUNDS,REG_UNONPOSIX}
+(1 row)
+
+-- expectNomatch 21.40 PQR {((.)){0}(\2)} xxx
+select * from test_regex('((.)){0}(\2)', 'xxx', 'PQR');
+ test_regex
+--------------------------------------------
+ {3,REG_UBACKREF,REG_UBOUNDS,REG_UNONPOSIX}
+(1 row)
+
+-- expectMatch 21.41 NPQR {((.)){0}(\2){0}} xyz {} {} {} {}
+select * from test_regex('((.)){0}(\2){0}', 'xyz', 'NPQR');
+ test_regex
+------------------------------------------------------------
+ {3,REG_UBACKREF,REG_UBOUNDS,REG_UNONPOSIX,REG_UEMPTYMATCH}
+ {"",NULL,NULL,NULL}
+(2 rows)
+
-- doing 22 "multicharacter collating elements"
-- # again ugh
-- MCCEs are not implemented in Postgres, so we skip all these tests
diff --git a/src/test/modules/test_regex/sql/test_regex.sql b/src/test/modules/test_regex/sql/test_regex.sql
index 991f804cb67..bdc090103b1 100644
--- a/src/test/modules/test_regex/sql/test_regex.sql
+++ b/src/test/modules/test_regex/sql/test_regex.sql
@@ -1015,6 +1015,12 @@ select * from test_regex('(a*)*', 'bc', 'N');
select * from test_regex(' TO (([a-z0-9._]+|"([^"]+|"")+")+)', 'asd TO foo', 'M');
-- expectMatch 21.36 RPQ ((.))(\2){0} xy x x x {}
select * from test_regex('((.))(\2){0}', 'xy', 'RPQ');
+-- expectNomatch 21.39 PQR {(.){0}(\1)} xxx
+select * from test_regex('(.){0}(\1)', 'xxx', 'PQR');
+-- expectNomatch 21.40 PQR {((.)){0}(\2)} xxx
+select * from test_regex('((.)){0}(\2)', 'xxx', 'PQR');
+-- expectMatch 21.41 NPQR {((.)){0}(\2){0}} xyz {} {} {} {}
+select * from test_regex('((.)){0}(\2){0}', 'xyz', 'NPQR');
-- doing 22 "multicharacter collating elements"
-- # again ugh
diff --git a/src/test/regress/expected/regex.out b/src/test/regress/expected/regex.out
index cbe2cfc3ea1..ae0de7307db 100644
--- a/src/test/regress/expected/regex.out
+++ b/src/test/regress/expected/regex.out
@@ -567,6 +567,25 @@ select 'a' ~ '()+\1';
t
(1 row)
+-- Test incorrect removal of capture groups within {0}
+select 'xxx' ~ '(.){0}(\1)' as f;
+ f
+---
+ f
+(1 row)
+
+select 'xxx' ~ '((.)){0}(\2)' as f;
+ f
+---
+ f
+(1 row)
+
+select 'xyz' ~ '((.)){0}(\2){0}' as t;
+ t
+---
+ t
+(1 row)
+
-- Test ancient oversight in when to apply zaptreesubs
select 'abcdef' ~ '^(.)\1|\1.' as f;
f
diff --git a/src/test/regress/sql/regex.sql b/src/test/regress/sql/regex.sql
index c6974a43d11..56217104ce6 100644
--- a/src/test/regress/sql/regex.sql
+++ b/src/test/regress/sql/regex.sql
@@ -135,6 +135,11 @@ select 'a' ~ '.. ()|\1';
select 'a' ~ '()*\1';
select 'a' ~ '()+\1';
+-- Test incorrect removal of capture groups within {0}
+select 'xxx' ~ '(.){0}(\1)' as f;
+select 'xxx' ~ '((.)){0}(\2)' as f;
+select 'xyz' ~ '((.)){0}(\2){0}' as t;
+
-- Test ancient oversight in when to apply zaptreesubs
select 'abcdef' ~ '^(.)\1|\1.' as f;
select 'abadef' ~ '^((.)\2|..)\2' as f;