BUG#26881 - Large MERGE tables report incorrect specification when no

            differences in tables
Certain merge tables were wrongly reported as having incorrect definition:
- Some fields that are 1 byte long (e.g. TINYINT, CHAR(1)), might
  be internally casted (in certain cases) to a different type on a
  storage engine layer. (affects 4.1 and up)
- If tables in a merge (and a MERGE table itself) had short VARCHAR column (less
  than 4 bytes) and at least one (but not all) tables were ALTER'ed (even to an
  identical table: ALTER TABLE xxx ENGINE=yyy), table definitions went ouf of
  sync. (affects 4.1 only)

This is fixed by relaxing a check for underlying conformance and setting
field type to FIELD_TYPE_STRING in case varchar is shorter than 4
when a table is created.

1 files changed, 4 insertions, 0 deletions

diff --git a/myisam/mi_create.c b/myisam/mi_create.c
index da9e0887b00..5e363a4e670 100644
--- a/myisam/mi_create.c
+++ b/myisam/mi_create.c
@@ -158,6 +158,10 @@ int mi_create(const char *name,uint keys,MI_KEYDEF *keydefs,
       rec--;
       if (rec->type == (int) FIELD_SKIP_ZERO && rec->length == 1)
       {
+        /*
+          NOTE1: here we change a field type FIELD_SKIP_ZERO ->
+          FIELD_NORMAL
+        */
 	rec->type=(int) FIELD_NORMAL;
 	packed--;
 	min_pack_length++;