Problem description:
Table 't' created with two colums having compound index on both the
columns under innodb/myisam engine at remote machine. In the local
machine same table is created undet the federated engine.
A select having where clause with along 'AND' operation gives wrong
results on local machine.
Analysis:
The given query at federated engine is wrongly transformed by
federated::create_where_from_key() function and the same was sent to
the remote machine. Hence the local machine is showing wrong results.
Given query "select c1 from t where c1 <= 2 and c2 = 1;"
Query transformed, after ha_federated::create_where_from_key() function is:
SELECT `c1`, `c2` FROM `t` WHERE (`c1` IS NOT NULL ) AND
( (`c1` >= 2) AND (`c2` <= 1) ) and the same sent to real_query().
In the above the '<=' and '=' conditions were transformed to '>=' and
'<=' respectively.
ha_federated::create_where_from_key() function behaving as below:
The key_range is having both the start_key and end_key. The start_key
is used to get "(`c1` IS NOT NULL )" part of the where clause, this
transformation is correct. The end_key is used to get "( (`c1` >= 2)
AND (`c2` <= 1) )", which is wrong, here the given conditions('<=' and '=')
are changed as wrong conditions('>=' and '<=').
The end_key is having {key = 0x39fa6d0 "", length = 10, keypart_map = 3,
flag = HA_READ_AFTER_KEY}
The store_length is having value '5'. Based on store_length and length
values the condition values is applied in HA_READ_AFTER_KEY switch case.
The switch case 'HA_READ_AFTER_KEY' is applicable to only the last part of
the end_key and for previous parts it is going to 'HA_READ_KEY_OR_NEXT' case,
here the '>=' is getting added as a condition instead of '<='.
Fix:
Updated the 'if' condition in 'HA_READ_AFTER_KEY' case to affect for all
parts of the end_key. i.e 'i > 0' will used for end_key, Hence added it in
the if condition.
As presently PARTITIONS + FEDERATED just doesn't work i added error message
to inform user about that.
Should be enabled again after releted WL's completion.
