Bug #29157: UPDATE, changed rows incorrect

Sometimes the number of really updated rows (with changed
column values) cannot be determined at the server level
alone (e.g. if the storage engine does not return enough
column values to verify that). So the only dependable way
in such cases is to let the storage engine return that
information if possible.
Fixed the bug at server level by providing a way for the 
storage engine to return information about wether it 
actually updated the row or the old and the new column 
values are the same. It can do that by returning 
HA_ERR_RECORD_IS_THE_SAME in ha_update_row().
Note that each storage engine may choose not to try to
return this status code, so this behaviour remains 
storage engine specific.

1 files changed, 3 insertions, 1 deletions

diff --git a/include/my_base.h b/include/my_base.h
index 617cdb8c3f0..b2a8b4b6b67 100644
--- a/include/my_base.h
+++ b/include/my_base.h
@@ -396,7 +396,9 @@ enum ha_base_keytype {
 #define HA_ERR_AUTOINC_READ_FAILED 166   /* Failed to get next autoinc value */
 #define HA_ERR_AUTOINC_ERANGE    167     /* Failed to set row autoinc value */
 #define HA_ERR_GENERIC           168     /* Generic error */
-#define HA_ERR_LAST              168 /*Copy last error nr.*/
+#define HA_ERR_RECORD_IS_THE_SAME 169    /* row not actually updated : 
+                                            new values same as the old values */
+#define HA_ERR_LAST              169 /*Copy last error nr.*/
 /* Add error numbers before HA_ERR_LAST and change it accordingly. */
 #define HA_ERR_ERRORS            (HA_ERR_LAST - HA_ERR_FIRST + 1)