Let TABLE_SHARE::tdc.free_tables, TABLE_SHARE::tdc.all_tables,
TABLE_SHARE::tdc.flushed and corresponding invariants be protected by
per-share TABLE_SHARE::tdc.LOCK_table_share instead of global LOCK_open.
Reduced number of my_hash_sort_bin() calls from 4 to 1 per query.
Reduced number of memory accesses done by my_hash_sort_bin().
Details:
- let MDL subsystem use pre-calculated hash value for hash
inserts and deletes
- let table cache use pre-calculated MDL hash value
- MDL namespace is excluded from hash value calculation, so that
hash value can be used by table cache as is
- hash value for MDL is calculated as resulting hash value + MDL
namespace
- extended hash implementation to accept user defined hash function
Move TABLE::in_use out of LOCK_open.
This is done with assumtion that foreign threads accessing TABLE::in_use
will only need consistent value _after_ marking table for flush and purging
unused table instances. In this case TABLE::in_use will always point to a
valid thread object.
Previously FLUSH TABLES thread may wait for tables flushed subsequently by
concurrent threads which breaks the above assumption, e.g.:
open tables: t1 (version= 1)
thr1 (FLUSH TABLES): refresh_version++
thr1 (FLUSH TABLES): purge table cache
open tables: none
thr2 (SELECT * FROM t1): open tables: t1
open tables: t1 (version= 2)
thr2 (FLUSH TABLES): refresh_version++
thr2 (FLUSH TABLES): purge table cache
thr1 (FLUSH TABLES): wait for old tables (including t1 with version 2)
It is fixed so that FLUSH TABLES waits only for tables that were open
heretofore.
Following variables do not require LOCK_open protection anymore:
- table_def_cache (renamed to tdc_hash) is protected by rw-lock
LOCK_tdc_hash;
- table_def_shutdown_in_progress doesn't need LOCK_open protection;
- last_table_id use atomics;
- TABLE_SHARE::ref_count (renamed to TABLE_SHARE::tdc.ref_count)
is protected by TABLE_SHARE::tdc.LOCK_table_share;
- TABLE_SHARE::next, ::prev (renamed to tdc.next and tdc.prev),
oldest_unused_share, end_of_unused_share are protected by
LOCK_unused_shares;
- TABLE_SHARE::m_flush_tickets (renamed to tdc.m_flush_tickets)
is protected by TABLE_SHARE::tdc.LOCK_table_share;
- refresh_version (renamed to tdc_version) use atomics.
