MDEV-33344 REGEXP empty string inconsistent

mysql-test/main/func_regexp.result

@@ -110,7 +110,7 @@ R2
 R3
 deallocate prepare stmt1;
 drop table t1;
-End of 4.1 tests
+# End of 4.1 tests
 SELECT 1 REGEXP NULL;
 1 REGEXP NULL
 NULL
@@ -126,7 +126,7 @@ NULL
 SELECT "ABC" REGEXP BINARY NULL;
 "ABC" REGEXP BINARY NULL
 NULL
-End of 5.0 tests
+# End of 5.0 tests
 CREATE TABLE t1(a INT, b CHAR(4));
 INSERT INTO t1 VALUES (1, '6.1'), (1, '7.0'), (1, '8.0');
 PREPARE stmt1 FROM "SELECT a FROM t1 WHERE a=1 AND '7.0' REGEXP b LIMIT 1";
@@ -144,7 +144,7 @@ a
 1
 DEALLOCATE PREPARE stmt1;
 DROP TABLE t1;
-End of 5.1 tests
+# End of 5.1 tests
 SELECT ' '  REGEXP '[[:blank:]]';
 ' '  REGEXP '[[:blank:]]'
 1
@@ -163,3 +163,19 @@ SELECT '\t' REGEXP '[[:space:]]';
 SELECT REGEXP_INSTR('111222333',2);
 REGEXP_INSTR('111222333',2)
 4
+# End of 10.3 tests
+#
+# MDEV-33344 REGEXP empty string inconsistent
+#
+create table t1 (x char(5));
+insert t1 values (''), ('x');
+select 'foo' regexp x from t1 order by x asc;
+'foo' regexp x
+1
+0
+select 'foo' regexp x from t1 order by x desc;
+'foo' regexp x
+0
+1
+drop table t1;
+# End of 10.5 tests

mysql-test/main/func_regexp.test

@@ -55,7 +55,7 @@ execute stmt1 using @a;
 deallocate prepare stmt1;
 drop table t1;
 
---echo End of 4.1 tests
+--echo # End of 4.1 tests
 
 
 #
@@ -74,7 +74,7 @@ SELECT NULL REGEXP BINARY NULL;
 SELECT 'A' REGEXP BINARY NULL;
 SELECT "ABC" REGEXP BINARY NULL;
 
---echo End of 5.0 tests
+--echo # End of 5.0 tests
 
 
 #
@@ -91,7 +91,7 @@ DEALLOCATE PREPARE stmt1;
 DROP TABLE t1;
 
 
---echo End of 5.1 tests
+--echo # End of 5.1 tests
 
 #
 # MDEV-5820 MySQL Bug #54805 definitions in regex/my_regex.h conflict with /usr/include/regex.h
@@ -110,3 +110,15 @@ SELECT '\t' REGEXP '[[:space:]]';
 --echo #
 SELECT REGEXP_INSTR('111222333',2);
 
+--echo # End of 10.3 tests
+
+--echo #
+--echo # MDEV-33344 REGEXP empty string inconsistent
+--echo #
+create table t1 (x char(5));
+insert t1 values (''), ('x');
+select 'foo' regexp x from t1 order by x asc;
+select 'foo' regexp x from t1 order by x desc;
+drop table t1;
+
+--echo # End of 10.5 tests

sql/item_cmpfunc.cc

@@ -6062,8 +6062,8 @@ bool Regexp_processor_pcre::compile(String *pattern, bool send_error)
     if (!stringcmp(pattern, &m_prev_pattern))
       return false;
     cleanup();
-    m_prev_pattern.copy(*pattern);
   }
+  m_prev_pattern.copy(*pattern);
 
   if (!(pattern= convert_if_needed(pattern, &pattern_converter)))
     return true;