Partitioning storage now supports MRR but doesn't support Index Condition
Pushdown (aka ICP). This causes counter-intuitive query plans for queries
that use BKA and conditions that depend on index fields:
- If the condition refers to other tables, BKA's variant of ICP is used
to handle it.
- If the condition depends on this table only, the optimizer will try to
use regular ICP for it, which will fail because the storage engine
doesn't support ICP.
Make the optimizer be smarter in the second case: if we were not able to
use regular ICP, use BKA's variant of ICP..
Fix partitioning and DS-MRR to work together
- In ha_partition::index_end(): take into account that ha_innobase (and
other engines using DS-MRR) will have inited=RND when initialized for
DS-MRR scan.
- In ha_partition::multi_range_read_next(): if the MRR scan is using
HA_MRR_NO_ASSOCIATION mode, it is not guaranteed that the partition's
handler will store anything into *range_info.
- In DsMrr_impl::choose_mrr_impl(): ha_partition will inquire partitions
about how much memory their MRR implementation needs by passing
*buffer_size=0. DS-MRR code didn't know about this (actually it used
uint for buffer size calculation and would have an under-flow).
Returning *buffer_size=0 made ha_partition assume that partitions do
not need MRR memory and pass the same buffer to each of them.
Now, this is fixed. If DS-MRR gets *buffer_size=0, it will return
the amount of buffer space needed, but not more than about
@@mrr_buffer_size.
* Fix ha_{innobase,maria,myisam}::clone. If ha_partition uses MRR on its
partitions, and partition use DS-MRR, the code will call handler->clone
with TABLE (*NOT partition*) name as an argument.
DS-MRR has no way of knowing the partition name, so the solution was
to have the ::clone() function for the affected storage engine to ignore
the name argument and get it elsewhere.
