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Diffstat (limited to 'sql/table_cache.cc')
| -rw-r--r-- | sql/table_cache.cc | 1293 |
1 files changed, 1293 insertions, 0 deletions
diff --git a/sql/table_cache.cc b/sql/table_cache.cc new file mode 100644 index 00000000..62ccfba7 --- /dev/null +++ b/sql/table_cache.cc @@ -0,0 +1,1293 @@ +/* Copyright (c) 2000, 2012, Oracle and/or its affiliates. + Copyright (c) 2010, 2011 Monty Program Ab + Copyright (C) 2013 Sergey Vojtovich and MariaDB Foundation + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; version 2 of the License. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software + Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */ + +/** + @file + Table definition cache and table cache implementation. + + Table definition cache actions: + - add new TABLE_SHARE object to cache (tdc_acquire_share()) + - acquire TABLE_SHARE object from cache (tdc_acquire_share()) + - release TABLE_SHARE object to cache (tdc_release_share()) + - purge unused TABLE_SHARE objects from cache (tdc_purge()) + - remove TABLE_SHARE object from cache (tdc_remove_table()) + - get number of TABLE_SHARE objects in cache (tdc_records()) + + Table cache actions: + - add new TABLE object to cache (tc_add_table()) + - acquire TABLE object from cache (tc_acquire_table()) + - release TABLE object to cache (tc_release_table()) + - purge unused TABLE objects from cache (tc_purge()) + - purge unused TABLE objects of a table from cache (tdc_remove_table()) + - get number of TABLE objects in cache (tc_records()) + + Dependencies: + - close_cached_tables(): flush tables on shutdown + - alloc_table_share() + - free_table_share() + + Table cache invariants: + - TABLE_SHARE::free_tables shall not contain objects with TABLE::in_use != 0 + - TABLE_SHARE::free_tables shall not receive new objects if + TABLE_SHARE::tdc.flushed is true +*/ + +#include "mariadb.h" +#include "lf.h" +#include "table.h" +#include "sql_base.h" + + +/** Configuration. */ +ulong tdc_size; /**< Table definition cache threshold for LRU eviction. */ +ulong tc_size; /**< Table cache threshold for LRU eviction. */ +uint32 tc_instances; +static std::atomic<uint32_t> tc_active_instances(1); +static std::atomic<bool> tc_contention_warning_reported; + +/** Data collections. */ +static LF_HASH tdc_hash; /**< Collection of TABLE_SHARE objects. */ +/** Collection of unused TABLE_SHARE objects. */ +static +I_P_List <TDC_element, + I_P_List_adapter<TDC_element, &TDC_element::next, &TDC_element::prev>, + I_P_List_null_counter, + I_P_List_fast_push_back<TDC_element> > unused_shares; + +static bool tdc_inited; + + +/** + Protects unused shares list. + + TDC_element::prev + TDC_element::next + unused_shares +*/ + +static mysql_mutex_t LOCK_unused_shares; + +#ifdef HAVE_PSI_INTERFACE +static PSI_mutex_key key_LOCK_unused_shares, key_TABLE_SHARE_LOCK_table_share, + key_LOCK_table_cache; +static PSI_mutex_info all_tc_mutexes[]= +{ + { &key_LOCK_unused_shares, "LOCK_unused_shares", PSI_FLAG_GLOBAL }, + { &key_TABLE_SHARE_LOCK_table_share, "TABLE_SHARE::tdc.LOCK_table_share", 0 }, + { &key_LOCK_table_cache, "LOCK_table_cache", 0 } +}; + +static PSI_cond_key key_TABLE_SHARE_COND_release; +static PSI_cond_info all_tc_conds[]= +{ + { &key_TABLE_SHARE_COND_release, "TABLE_SHARE::tdc.COND_release", 0 } +}; +#endif + + +static int fix_thd_pins(THD *thd) +{ + return thd->tdc_hash_pins ? 0 : + (thd->tdc_hash_pins= lf_hash_get_pins(&tdc_hash)) == 0; +} + + +/* + Auxiliary routines for manipulating with per-share all/unused lists + and tc_count counter. + Responsible for preserving invariants between those lists, counter + and TABLE::in_use member. + In fact those routines implement sort of implicit table cache as + part of table definition cache. +*/ + +struct Table_cache_instance +{ + /** + Protects free_tables (TABLE::global_free_next and TABLE::global_free_prev), + records, Share_free_tables::List (TABLE::prev and TABLE::next), + TABLE::in_use. + */ + mysql_mutex_t LOCK_table_cache; + I_P_List <TABLE, I_P_List_adapter<TABLE, &TABLE::global_free_next, + &TABLE::global_free_prev>, + I_P_List_null_counter, I_P_List_fast_push_back<TABLE> > + free_tables; + ulong records; + uint mutex_waits; + uint mutex_nowaits; + /** Avoid false sharing between instances */ + char pad[CPU_LEVEL1_DCACHE_LINESIZE]; + + Table_cache_instance(): records(0), mutex_waits(0), mutex_nowaits(0) + { + mysql_mutex_init(key_LOCK_table_cache, &LOCK_table_cache, + MY_MUTEX_INIT_FAST); + } + + ~Table_cache_instance() + { + mysql_mutex_destroy(&LOCK_table_cache); + DBUG_ASSERT(free_tables.is_empty()); + DBUG_ASSERT(records == 0); + } + + /** + Lock table cache mutex and check contention. + + Instance is considered contested if more than 20% of mutex acquisiotions + can't be served immediately. Up to 100 000 probes may be performed to avoid + instance activation on short sporadic peaks. 100 000 is estimated maximum + number of queries one instance can serve in one second. + + These numbers work well on a 2 socket / 20 core / 40 threads Intel Broadwell + system, that is expected number of instances is activated within reasonable + warmup time. It may have to be adjusted for other systems. + + Only TABLE object acquistion is instrumented. We intentionally avoid this + overhead on TABLE object release. All other table cache mutex acquistions + are considered out of hot path and are not instrumented either. + */ + void lock_and_check_contention(uint32_t n_instances, uint32_t instance) + { + if (mysql_mutex_trylock(&LOCK_table_cache)) + { + mysql_mutex_lock(&LOCK_table_cache); + if (++mutex_waits == 20000) + { + if (n_instances < tc_instances) + { + if (tc_active_instances. + compare_exchange_weak(n_instances, n_instances + 1, + std::memory_order_relaxed, + std::memory_order_relaxed)) + { + sql_print_information("Detected table cache mutex contention at instance %d: " + "%d%% waits. Additional table cache instance " + "activated. Number of instances after " + "activation: %d.", + instance + 1, + mutex_waits * 100 / (mutex_nowaits + mutex_waits), + n_instances + 1); + } + } + else if (!tc_contention_warning_reported.exchange(true, + std::memory_order_relaxed)) + { + sql_print_warning("Detected table cache mutex contention at instance %d: " + "%d%% waits. Additional table cache instance " + "cannot be activated: consider raising " + "table_open_cache_instances. Number of active " + "instances: %d.", + instance + 1, + mutex_waits * 100 / (mutex_nowaits + mutex_waits), + n_instances); + } + mutex_waits= 0; + mutex_nowaits= 0; + } + } + else if (++mutex_nowaits == 80000) + { + mutex_waits= 0; + mutex_nowaits= 0; + } + } +}; + + +static Table_cache_instance *tc; + + +static void intern_close_table(TABLE *table) +{ + delete table->triggers; + DBUG_ASSERT(table->file); + closefrm(table); + tdc_release_share(table->s); + my_free(table); +} + + +/** + Get number of TABLE objects (used and unused) in table cache. +*/ + +uint tc_records(void) +{ + ulong total= 0; + for (uint32 i= 0; i < tc_instances; i++) + { + mysql_mutex_lock(&tc[i].LOCK_table_cache); + total+= tc[i].records; + mysql_mutex_unlock(&tc[i].LOCK_table_cache); + } + return total; +} + + +/** + Remove TABLE object from table cache. +*/ + +static void tc_remove_table(TABLE *table) +{ + TDC_element *element= table->s->tdc; + + mysql_mutex_lock(&element->LOCK_table_share); + /* Wait for MDL deadlock detector to complete traversing tdc.all_tables. */ + while (element->all_tables_refs) + mysql_cond_wait(&element->COND_release, &element->LOCK_table_share); + element->all_tables.remove(table); + mysql_mutex_unlock(&element->LOCK_table_share); + + intern_close_table(table); +} + + +static void tc_remove_all_unused_tables(TDC_element *element, + Share_free_tables::List *purge_tables) +{ + for (uint32 i= 0; i < tc_instances; i++) + { + mysql_mutex_lock(&tc[i].LOCK_table_cache); + while (auto table= element->free_tables[i].list.pop_front()) + { + tc[i].records--; + tc[i].free_tables.remove(table); + DBUG_ASSERT(element->all_tables_refs == 0); + element->all_tables.remove(table); + purge_tables->push_front(table); + } + mysql_mutex_unlock(&tc[i].LOCK_table_cache); + } +} + + +/** + Free all unused TABLE objects. + + While locked: + - remove unused objects from TABLE_SHARE::tdc.free_tables and + TABLE_SHARE::tdc.all_tables + - decrement tc_count + + While unlocked: + - free resources related to unused objects + + @note This is called by 'handle_manager' when one wants to + periodicly flush all not used tables. +*/ + +static my_bool tc_purge_callback(TDC_element *element, + Share_free_tables::List *purge_tables) +{ + mysql_mutex_lock(&element->LOCK_table_share); + tc_remove_all_unused_tables(element, purge_tables); + mysql_mutex_unlock(&element->LOCK_table_share); + return FALSE; +} + + +void tc_purge() +{ + Share_free_tables::List purge_tables; + + tdc_iterate(0, (my_hash_walk_action) tc_purge_callback, &purge_tables); + while (auto table= purge_tables.pop_front()) + intern_close_table(table); +} + + +/** + Add new TABLE object to table cache. + + @pre TABLE object is used by caller. + + Added object cannot be evicted or acquired. + + While locked: + - add object to TABLE_SHARE::tdc.all_tables + - increment tc_count + - evict LRU object from table cache if we reached threshold + + While unlocked: + - free evicted object +*/ + +void tc_add_table(THD *thd, TABLE *table) +{ + uint32_t i= + thd->thread_id % tc_active_instances.load(std::memory_order_relaxed); + TABLE *LRU_table= 0; + TDC_element *element= table->s->tdc; + + DBUG_ASSERT(table->in_use == thd); + table->instance= i; + mysql_mutex_lock(&element->LOCK_table_share); + /* Wait for MDL deadlock detector to complete traversing tdc.all_tables. */ + while (element->all_tables_refs) + mysql_cond_wait(&element->COND_release, &element->LOCK_table_share); + element->all_tables.push_front(table); + mysql_mutex_unlock(&element->LOCK_table_share); + + mysql_mutex_lock(&tc[i].LOCK_table_cache); + if (tc[i].records == tc_size) + { + if ((LRU_table= tc[i].free_tables.pop_front())) + { + LRU_table->s->tdc->free_tables[i].list.remove(LRU_table); + /* Needed if MDL deadlock detector chimes in before tc_remove_table() */ + LRU_table->in_use= thd; + mysql_mutex_unlock(&tc[i].LOCK_table_cache); + /* Keep out of locked LOCK_table_cache */ + tc_remove_table(LRU_table); + } + else + { + tc[i].records++; + mysql_mutex_unlock(&tc[i].LOCK_table_cache); + } + /* Keep out of locked LOCK_table_cache */ + status_var_increment(thd->status_var.table_open_cache_overflows); + } + else + { + tc[i].records++; + mysql_mutex_unlock(&tc[i].LOCK_table_cache); + } +} + + +/** + Acquire TABLE object from table cache. + + @pre share must be protected against removal. + + Acquired object cannot be evicted or acquired again. + + @return TABLE object, or NULL if no unused objects. +*/ + +TABLE *tc_acquire_table(THD *thd, TDC_element *element) +{ + uint32_t n_instances= tc_active_instances.load(std::memory_order_relaxed); + uint32_t i= thd->thread_id % n_instances; + TABLE *table; + + tc[i].lock_and_check_contention(n_instances, i); + table= element->free_tables[i].list.pop_front(); + if (table) + { + DBUG_ASSERT(!table->in_use); + table->in_use= thd; + /* The ex-unused table must be fully functional. */ + DBUG_ASSERT(table->db_stat && table->file); + /* The children must be detached from the table. */ + DBUG_ASSERT(!table->file->extra(HA_EXTRA_IS_ATTACHED_CHILDREN)); + tc[i].free_tables.remove(table); + } + mysql_mutex_unlock(&tc[i].LOCK_table_cache); + return table; +} + + +/** + Release TABLE object to table cache. + + @pre object is used by caller. + + Released object may be evicted or acquired again. + + While locked: + - if object is marked for purge, decrement tc_count + - add object to TABLE_SHARE::tdc.free_tables + - evict LRU object from table cache if we reached threshold + + While unlocked: + - mark object not in use by any thread + - free evicted/purged object + + @note Another thread may mark share for purge any moment (even + after version check). It means to-be-purged object may go to + unused lists. This other thread is expected to call tc_purge(), + which is synchronized with us on TABLE_SHARE::tdc.LOCK_table_share. + + @return + @retval true object purged + @retval false object released +*/ + +void tc_release_table(TABLE *table) +{ + uint32 i= table->instance; + DBUG_ENTER("tc_release_table"); + DBUG_ASSERT(table->in_use); + DBUG_ASSERT(table->file); + DBUG_ASSERT(!table->pos_in_locked_tables); + + mysql_mutex_lock(&tc[i].LOCK_table_cache); + if (table->needs_reopen() || table->s->tdc->flushed || + tc[i].records > tc_size) + { + tc[i].records--; + mysql_mutex_unlock(&tc[i].LOCK_table_cache); + tc_remove_table(table); + } + else + { + table->in_use= 0; + table->s->tdc->free_tables[i].list.push_front(table); + tc[i].free_tables.push_back(table); + mysql_mutex_unlock(&tc[i].LOCK_table_cache); + } + DBUG_VOID_RETURN; +} + + +static void tdc_assert_clean_share(TDC_element *element) +{ + DBUG_ASSERT(element->share == 0); + DBUG_ASSERT(element->ref_count == 0); + DBUG_ASSERT(element->m_flush_tickets.is_empty()); + DBUG_ASSERT(element->all_tables.is_empty()); +#ifndef DBUG_OFF + for (uint32 i= 0; i < tc_instances; i++) + DBUG_ASSERT(element->free_tables[i].list.is_empty()); +#endif + DBUG_ASSERT(element->all_tables_refs == 0); + DBUG_ASSERT(element->next == 0); + DBUG_ASSERT(element->prev == 0); +} + + +/** + Delete share from hash and free share object. +*/ + +static void tdc_delete_share_from_hash(TDC_element *element) +{ + THD *thd= current_thd; + LF_PINS *pins; + TABLE_SHARE *share; + DBUG_ENTER("tdc_delete_share_from_hash"); + + mysql_mutex_assert_owner(&element->LOCK_table_share); + share= element->share; + DBUG_ASSERT(share); + element->share= 0; + PSI_CALL_release_table_share(share->m_psi); + share->m_psi= 0; + + if (!element->m_flush_tickets.is_empty()) + { + Wait_for_flush_list::Iterator it(element->m_flush_tickets); + Wait_for_flush *ticket; + while ((ticket= it++)) + (void) ticket->get_ctx()->m_wait.set_status(MDL_wait::GRANTED); + + do + { + mysql_cond_wait(&element->COND_release, &element->LOCK_table_share); + } while (!element->m_flush_tickets.is_empty()); + } + + mysql_mutex_unlock(&element->LOCK_table_share); + + if (thd) + { + fix_thd_pins(thd); + pins= thd->tdc_hash_pins; + } + else + pins= lf_hash_get_pins(&tdc_hash); + + DBUG_ASSERT(pins); // What can we do about it? + tdc_assert_clean_share(element); + lf_hash_delete(&tdc_hash, pins, element->m_key, element->m_key_length); + if (!thd) + lf_hash_put_pins(pins); + free_table_share(share); + DBUG_VOID_RETURN; +} + + +/** + Prepeare table share for use with table definition cache. +*/ + +static void lf_alloc_constructor(uchar *arg) +{ + TDC_element *element= (TDC_element*) (arg + LF_HASH_OVERHEAD); + DBUG_ENTER("lf_alloc_constructor"); + mysql_mutex_init(key_TABLE_SHARE_LOCK_table_share, + &element->LOCK_table_share, MY_MUTEX_INIT_FAST); + mysql_cond_init(key_TABLE_SHARE_COND_release, &element->COND_release, 0); + element->m_flush_tickets.empty(); + element->all_tables.empty(); + for (uint32 i= 0; i < tc_instances; i++) + element->free_tables[i].list.empty(); + element->all_tables_refs= 0; + element->share= 0; + element->ref_count= 0; + element->next= 0; + element->prev= 0; + DBUG_VOID_RETURN; +} + + +/** + Release table definition cache specific resources of table share. +*/ + +static void lf_alloc_destructor(uchar *arg) +{ + TDC_element *element= (TDC_element*) (arg + LF_HASH_OVERHEAD); + DBUG_ENTER("lf_alloc_destructor"); + tdc_assert_clean_share(element); + mysql_cond_destroy(&element->COND_release); + mysql_mutex_destroy(&element->LOCK_table_share); + DBUG_VOID_RETURN; +} + + +static void tdc_hash_initializer(LF_HASH *, + TDC_element *element, LEX_STRING *key) +{ + memcpy(element->m_key, key->str, key->length); + element->m_key_length= (uint)key->length; + tdc_assert_clean_share(element); +} + + +static uchar *tdc_hash_key(const TDC_element *element, size_t *length, + my_bool) +{ + *length= element->m_key_length; + return (uchar*) element->m_key; +} + + +/** + Initialize table definition cache. +*/ + +bool tdc_init(void) +{ + DBUG_ENTER("tdc_init"); +#ifdef HAVE_PSI_INTERFACE + mysql_mutex_register("sql", all_tc_mutexes, array_elements(all_tc_mutexes)); + mysql_cond_register("sql", all_tc_conds, array_elements(all_tc_conds)); +#endif + /* Extra instance is allocated to avoid false sharing */ + if (!(tc= new Table_cache_instance[tc_instances + 1])) + DBUG_RETURN(true); + tdc_inited= true; + mysql_mutex_init(key_LOCK_unused_shares, &LOCK_unused_shares, + MY_MUTEX_INIT_FAST); + lf_hash_init(&tdc_hash, sizeof(TDC_element) + + sizeof(Share_free_tables) * (tc_instances - 1), + LF_HASH_UNIQUE, 0, 0, + (my_hash_get_key) tdc_hash_key, + &my_charset_bin); + tdc_hash.alloc.constructor= lf_alloc_constructor; + tdc_hash.alloc.destructor= lf_alloc_destructor; + tdc_hash.initializer= (lf_hash_initializer) tdc_hash_initializer; + DBUG_RETURN(false); +} + + +/** + Notify table definition cache that process of shutting down server + has started so it has to keep number of TABLE and TABLE_SHARE objects + minimal in order to reduce number of references to pluggable engines. +*/ + +void tdc_start_shutdown(void) +{ + DBUG_ENTER("tdc_start_shutdown"); + if (tdc_inited) + { + /* + Ensure that TABLE and TABLE_SHARE objects which are created for + tables that are open during process of plugins' shutdown are + immediately released. This keeps number of references to engine + plugins minimal and allows shutdown to proceed smoothly. + */ + tdc_size= 0; + tc_size= 0; + /* Free all cached but unused TABLEs and TABLE_SHAREs. */ + purge_tables(); + } + DBUG_VOID_RETURN; +} + + +/** + Deinitialize table definition cache. +*/ + +void tdc_deinit(void) +{ + DBUG_ENTER("tdc_deinit"); + if (tdc_inited) + { + tdc_inited= false; + lf_hash_destroy(&tdc_hash); + mysql_mutex_destroy(&LOCK_unused_shares); + delete [] tc; + } + DBUG_VOID_RETURN; +} + + +/** + Get number of cached table definitions. + + @return Number of cached table definitions +*/ + +ulong tdc_records(void) +{ + return lf_hash_size(&tdc_hash); +} + + +void tdc_purge(bool all) +{ + DBUG_ENTER("tdc_purge"); + while (all || tdc_records() > tdc_size) + { + TDC_element *element; + + mysql_mutex_lock(&LOCK_unused_shares); + if (!(element= unused_shares.pop_front())) + { + mysql_mutex_unlock(&LOCK_unused_shares); + break; + } + + /* Concurrent thread may start using share again, reset prev and next. */ + element->prev= 0; + element->next= 0; + mysql_mutex_lock(&element->LOCK_table_share); + if (element->ref_count) + { + mysql_mutex_unlock(&element->LOCK_table_share); + mysql_mutex_unlock(&LOCK_unused_shares); + continue; + } + mysql_mutex_unlock(&LOCK_unused_shares); + + tdc_delete_share_from_hash(element); + } + DBUG_VOID_RETURN; +} + + +/** + Lock table share. + + Find table share with given db.table_name in table definition cache. Return + locked table share if found. + + Locked table share means: + - table share is protected against removal from table definition cache + - no other thread can acquire/release table share + + Caller is expected to unlock table share with tdc_unlock_share(). + + @retval 0 Share not found + @retval MY_ERRPTR OOM + @retval ptr Pointer to locked table share +*/ + +TDC_element *tdc_lock_share(THD *thd, const char *db, const char *table_name) +{ + TDC_element *element; + char key[MAX_DBKEY_LENGTH]; + + DBUG_ENTER("tdc_lock_share"); + if (unlikely(fix_thd_pins(thd))) + DBUG_RETURN((TDC_element*) MY_ERRPTR); + + element= (TDC_element *) lf_hash_search(&tdc_hash, thd->tdc_hash_pins, + (uchar*) key, + tdc_create_key(key, db, table_name)); + if (element) + { + mysql_mutex_lock(&element->LOCK_table_share); + if (unlikely(!element->share || element->share->error)) + { + mysql_mutex_unlock(&element->LOCK_table_share); + element= 0; + } + lf_hash_search_unpin(thd->tdc_hash_pins); + } + + DBUG_RETURN(element); +} + + +/** + Unlock share locked by tdc_lock_share(). +*/ + +void tdc_unlock_share(TDC_element *element) +{ + DBUG_ENTER("tdc_unlock_share"); + mysql_mutex_unlock(&element->LOCK_table_share); + DBUG_VOID_RETURN; +} + + +int tdc_share_is_cached(THD *thd, const char *db, const char *table_name) +{ + char key[MAX_DBKEY_LENGTH]; + + if (unlikely(fix_thd_pins(thd))) + return -1; + + if (lf_hash_search(&tdc_hash, thd->tdc_hash_pins, (uchar*) key, + tdc_create_key(key, db, table_name))) + { + lf_hash_search_unpin(thd->tdc_hash_pins); + return 1; + } + return 0; +} + + +/* + Get TABLE_SHARE for a table. + + tdc_acquire_share() + thd Thread handle + tl Table that should be opened + flags operation: what to open table or view + out_table TABLE for the requested table + + IMPLEMENTATION + Get a table definition from the table definition cache. + If it doesn't exist, create a new from the table definition file. + + RETURN + 0 Error + # Share for table +*/ + +TABLE_SHARE *tdc_acquire_share(THD *thd, TABLE_LIST *tl, uint flags, + TABLE **out_table) +{ + TABLE_SHARE *share; + TDC_element *element; + const char *key; + uint key_length= get_table_def_key(tl, &key); + my_hash_value_type hash_value= tl->mdl_request.key.tc_hash_value(); + bool was_unused; + DBUG_ENTER("tdc_acquire_share"); + + if (fix_thd_pins(thd)) + DBUG_RETURN(0); + +retry: + while (!(element= (TDC_element*) lf_hash_search_using_hash_value(&tdc_hash, + thd->tdc_hash_pins, hash_value, (uchar*) key, key_length))) + { + LEX_STRING tmp= { const_cast<char*>(key), key_length }; + int res= lf_hash_insert(&tdc_hash, thd->tdc_hash_pins, (uchar*) &tmp); + + if (res == -1) + DBUG_RETURN(0); + else if (res == 1) + continue; + + element= (TDC_element*) lf_hash_search_using_hash_value(&tdc_hash, + thd->tdc_hash_pins, hash_value, (uchar*) key, key_length); + lf_hash_search_unpin(thd->tdc_hash_pins); + DBUG_ASSERT(element); + + if (!(share= alloc_table_share(tl->db.str, tl->table_name.str, key, key_length))) + { + lf_hash_delete(&tdc_hash, thd->tdc_hash_pins, key, key_length); + DBUG_RETURN(0); + } + + /* note that tdc_acquire_share() *always* uses discovery */ + open_table_def(thd, share, flags | GTS_USE_DISCOVERY); + + if (checked_unlikely(share->error)) + { + free_table_share(share); + lf_hash_delete(&tdc_hash, thd->tdc_hash_pins, key, key_length); + DBUG_RETURN(0); + } + + mysql_mutex_lock(&element->LOCK_table_share); + element->share= share; + share->tdc= element; + element->ref_count++; + element->flushed= false; + mysql_mutex_unlock(&element->LOCK_table_share); + + tdc_purge(false); + if (out_table) + { + status_var_increment(thd->status_var.table_open_cache_misses); + *out_table= 0; + } + share->m_psi= PSI_CALL_get_table_share(false, share); + goto end; + } + + /* cannot force discovery of a cached share */ + DBUG_ASSERT(!(flags & GTS_FORCE_DISCOVERY)); + + if (out_table && (flags & GTS_TABLE)) + { + if ((*out_table= tc_acquire_table(thd, element))) + { + lf_hash_search_unpin(thd->tdc_hash_pins); + DBUG_ASSERT(!(flags & GTS_NOLOCK)); + DBUG_ASSERT(element->share); + DBUG_ASSERT(!element->share->error); + DBUG_ASSERT(!element->share->is_view); + status_var_increment(thd->status_var.table_open_cache_hits); + DBUG_RETURN(element->share); + } + status_var_increment(thd->status_var.table_open_cache_misses); + } + + mysql_mutex_lock(&element->LOCK_table_share); + if (!(share= element->share)) + { + mysql_mutex_unlock(&element->LOCK_table_share); + lf_hash_search_unpin(thd->tdc_hash_pins); + goto retry; + } + lf_hash_search_unpin(thd->tdc_hash_pins); + + /* + We found an existing table definition. Return it if we didn't get + an error when reading the table definition from file. + */ + if (unlikely(share->error)) + { + open_table_error(share, share->error, share->open_errno); + goto err; + } + + if (share->is_view && !(flags & GTS_VIEW)) + { + open_table_error(share, OPEN_FRM_NOT_A_TABLE, ENOENT); + goto err; + } + if (!share->is_view && !(flags & GTS_TABLE)) + { + open_table_error(share, OPEN_FRM_NOT_A_VIEW, ENOENT); + goto err; + } + + was_unused= !element->ref_count; + element->ref_count++; + mysql_mutex_unlock(&element->LOCK_table_share); + if (was_unused) + { + mysql_mutex_lock(&LOCK_unused_shares); + if (element->prev) + { + /* + Share was not used before and it was in the old_unused_share list + Unlink share from this list + */ + DBUG_PRINT("info", ("Unlinking from not used list")); + unused_shares.remove(element); + element->next= 0; + element->prev= 0; + } + mysql_mutex_unlock(&LOCK_unused_shares); + } + +end: + DBUG_PRINT("exit", ("share: %p ref_count: %u", + share, share->tdc->ref_count)); + if (flags & GTS_NOLOCK) + { + tdc_release_share(share); + /* + if GTS_NOLOCK is requested, the returned share pointer cannot be used, + the share it points to may go away any moment. + But perhaps the caller is only interested to know whether a share or + table existed? + Let's return an invalid pointer here to catch dereferencing attempts. + */ + share= UNUSABLE_TABLE_SHARE; + } + DBUG_RETURN(share); + +err: + mysql_mutex_unlock(&element->LOCK_table_share); + DBUG_RETURN(0); +} + + +/** + Release table share acquired by tdc_acquire_share(). +*/ + +void tdc_release_share(TABLE_SHARE *share) +{ + DBUG_ENTER("tdc_release_share"); + + mysql_mutex_lock(&share->tdc->LOCK_table_share); + DBUG_PRINT("enter", + ("share: %p table: %s.%s ref_count: %u", + share, share->db.str, share->table_name.str, + share->tdc->ref_count)); + DBUG_ASSERT(share->tdc->ref_count); + + if (share->tdc->ref_count > 1) + { + share->tdc->ref_count--; + if (!share->is_view) + mysql_cond_broadcast(&share->tdc->COND_release); + mysql_mutex_unlock(&share->tdc->LOCK_table_share); + DBUG_VOID_RETURN; + } + mysql_mutex_unlock(&share->tdc->LOCK_table_share); + + mysql_mutex_lock(&LOCK_unused_shares); + mysql_mutex_lock(&share->tdc->LOCK_table_share); + if (--share->tdc->ref_count) + { + if (!share->is_view) + mysql_cond_broadcast(&share->tdc->COND_release); + mysql_mutex_unlock(&share->tdc->LOCK_table_share); + mysql_mutex_unlock(&LOCK_unused_shares); + DBUG_VOID_RETURN; + } + if (share->tdc->flushed || tdc_records() > tdc_size) + { + mysql_mutex_unlock(&LOCK_unused_shares); + tdc_delete_share_from_hash(share->tdc); + DBUG_VOID_RETURN; + } + /* Link share last in used_table_share list */ + DBUG_PRINT("info", ("moving share to unused list")); + DBUG_ASSERT(share->tdc->next == 0); + unused_shares.push_back(share->tdc); + mysql_mutex_unlock(&share->tdc->LOCK_table_share); + mysql_mutex_unlock(&LOCK_unused_shares); + DBUG_VOID_RETURN; +} + + +void tdc_remove_referenced_share(THD *thd, TABLE_SHARE *share) +{ + DBUG_ASSERT(thd->mdl_context.is_lock_owner(MDL_key::TABLE, share->db.str, + share->table_name.str, + MDL_EXCLUSIVE)); + share->tdc->flush_unused(false); + mysql_mutex_lock(&share->tdc->LOCK_table_share); + share->tdc->wait_for_refs(1); + DBUG_ASSERT(share->tdc->all_tables.is_empty()); + share->tdc->ref_count--; + tdc_delete_share_from_hash(share->tdc); +} + + +/** + Removes all TABLE instances and corresponding TABLE_SHARE + + @param thd Thread context + @param db Name of database + @param table_name Name of table + + @note It assumes that table instances are already not used by any + (other) thread (this should be achieved by using meta-data locks). +*/ + +void tdc_remove_table(THD *thd, const char *db, const char *table_name) +{ + TDC_element *element; + DBUG_ENTER("tdc_remove_table"); + DBUG_PRINT("enter", ("name: %s", table_name)); + + DBUG_ASSERT(thd->mdl_context.is_lock_owner(MDL_key::TABLE, db, table_name, + MDL_EXCLUSIVE)); + + mysql_mutex_lock(&LOCK_unused_shares); + if (!(element= tdc_lock_share(thd, db, table_name))) + { + mysql_mutex_unlock(&LOCK_unused_shares); + DBUG_VOID_RETURN; + } + + DBUG_ASSERT(element != MY_ERRPTR); // What can we do about it? + + if (!element->ref_count) + { + if (element->prev) + { + unused_shares.remove(element); + element->prev= 0; + element->next= 0; + } + mysql_mutex_unlock(&LOCK_unused_shares); + + tdc_delete_share_from_hash(element); + DBUG_VOID_RETURN; + } + mysql_mutex_unlock(&LOCK_unused_shares); + + element->ref_count++; + mysql_mutex_unlock(&element->LOCK_table_share); + + /* We have to relock the mutex to avoid code duplication. Sigh. */ + tdc_remove_referenced_share(thd, element->share); + DBUG_VOID_RETURN; +} + + +/** + Check if table's share is being removed from the table definition + cache and, if yes, wait until the flush is complete. + + @param thd Thread context. + @param table_list Table which share should be checked. + @param timeout Timeout for waiting. + @param deadlock_weight Weight of this wait for deadlock detector. + + @retval 0 Success. Share is up to date or has been flushed. + @retval 1 Error (OOM, was killed, the wait resulted + in a deadlock or timeout). Reported. +*/ + +int tdc_wait_for_old_version(THD *thd, const char *db, const char *table_name, + ulong wait_timeout, uint deadlock_weight) +{ + TDC_element *element; + + if (!(element= tdc_lock_share(thd, db, table_name))) + return FALSE; + else if (element == MY_ERRPTR) + return TRUE; + else if (element->flushed) + { + struct timespec abstime; + set_timespec(abstime, wait_timeout); + return element->share->wait_for_old_version(thd, &abstime, deadlock_weight); + } + tdc_unlock_share(element); + return FALSE; +} + + +/** + Iterate table definition cache. + + Object is protected against removal from table definition cache. + + @note Returned TABLE_SHARE is not guaranteed to be fully initialized: + tdc_acquire_share() added new share, but didn't open it yet. If caller + needs fully initializer share, it must lock table share mutex. +*/ + +struct eliminate_duplicates_arg +{ + HASH hash; + MEM_ROOT root; + my_hash_walk_action action; + void *argument; +}; + + +static uchar *eliminate_duplicates_get_key(const uchar *element, size_t *length, + my_bool not_used __attribute__((unused))) +{ + LEX_STRING *key= (LEX_STRING *) element; + *length= key->length; + return (uchar *) key->str; +} + + +static my_bool eliminate_duplicates(TDC_element *element, + eliminate_duplicates_arg *arg) +{ + LEX_STRING *key= (LEX_STRING *) alloc_root(&arg->root, sizeof(LEX_STRING)); + + if (!key || !(key->str= (char*) memdup_root(&arg->root, element->m_key, + element->m_key_length))) + return TRUE; + + key->length= element->m_key_length; + + if (my_hash_insert(&arg->hash, (uchar *) key)) + return FALSE; + + return arg->action(element, arg->argument); +} + + +int tdc_iterate(THD *thd, my_hash_walk_action action, void *argument, + bool no_dups) +{ + eliminate_duplicates_arg no_dups_argument; + LF_PINS *pins; + myf alloc_flags= 0; + uint hash_flags= HASH_UNIQUE; + int res; + + if (thd) + { + fix_thd_pins(thd); + pins= thd->tdc_hash_pins; + alloc_flags= MY_THREAD_SPECIFIC; + hash_flags|= HASH_THREAD_SPECIFIC; + } + else + pins= lf_hash_get_pins(&tdc_hash); + + if (!pins) + return ER_OUTOFMEMORY; + + if (no_dups) + { + init_alloc_root(PSI_INSTRUMENT_ME, &no_dups_argument.root, 4096, 4096, MYF(alloc_flags)); + my_hash_init(PSI_INSTRUMENT_ME, &no_dups_argument.hash, &my_charset_bin, + tdc_records(), 0, 0, eliminate_duplicates_get_key, 0, + hash_flags); + no_dups_argument.action= action; + no_dups_argument.argument= argument; + action= (my_hash_walk_action) eliminate_duplicates; + argument= &no_dups_argument; + } + + res= lf_hash_iterate(&tdc_hash, pins, action, argument); + + if (!thd) + lf_hash_put_pins(pins); + + if (no_dups) + { + my_hash_free(&no_dups_argument.hash); + free_root(&no_dups_argument.root, MYF(0)); + } + return res; +} + + +int show_tc_active_instances(THD *thd, SHOW_VAR *var, char *buff, + enum enum_var_type scope) +{ + var->type= SHOW_UINT; + var->value= buff; + *(reinterpret_cast<uint32_t*>(buff))= + tc_active_instances.load(std::memory_order_relaxed); + return 0; +} + + +/** + Waits until ref_count goes down to given number + + @param my_refs Number of references owned by the caller + + Caller must own at least one TABLE_SHARE reference. + + Even though current thread holds exclusive metadata lock on this share, + concurrent FLUSH TABLES threads may be in process of closing unused table + instances belonging to this share. E.g.: + thr1 (FLUSH TABLES): table= share->tdc.free_tables.pop_front(); + thr1 (FLUSH TABLES): share->tdc.all_tables.remove(table); + thr2 (ALTER TABLE): tdc_remove_table(); + thr1 (FLUSH TABLES): intern_close_table(table); + + Current remove type assumes that all table instances (except for those + that are owned by current thread) must be closed before + thd_remove_table() returns. Wait for such tables now. + + intern_close_table() decrements ref_count and signals COND_release. When + ref_count drops down to number of references owned by current thread + waiting is completed. + + Unfortunately TABLE_SHARE::wait_for_old_version() cannot be used here + because it waits for all table instances, whereas we have to wait only + for those that are not owned by current thread. +*/ + +void TDC_element::wait_for_refs(uint my_refs) +{ + while (ref_count > my_refs) + mysql_cond_wait(&COND_release, &LOCK_table_share); +} + + +/** + Flushes unused TABLE instances + + @param thd Thread context + @param mark_flushed Whether to destroy TABLE_SHARE when released + + Caller is allowed to own used TABLE instances. + There must be no TABLE objects used by other threads and caller must own + exclusive metadata lock on the table. +*/ + +void TDC_element::flush(THD *thd, bool mark_flushed) +{ + DBUG_ASSERT(thd->mdl_context.is_lock_owner(MDL_key::TABLE, share->db.str, + share->table_name.str, + MDL_EXCLUSIVE)); + + flush_unused(mark_flushed); + + mysql_mutex_lock(&LOCK_table_share); + All_share_tables_list::Iterator it(all_tables); + uint my_refs= 0; + while (auto table= it++) + { + if (table->in_use == thd) + my_refs++; + } + wait_for_refs(my_refs); +#ifndef DBUG_OFF + it.rewind(); + while (auto table= it++) + DBUG_ASSERT(table->in_use == thd); +#endif + mysql_mutex_unlock(&LOCK_table_share); +} + + +/** + Flushes unused TABLE instances +*/ + +void TDC_element::flush_unused(bool mark_flushed) +{ + Share_free_tables::List purge_tables; + + mysql_mutex_lock(&LOCK_table_share); + if (mark_flushed) + flushed= true; + tc_remove_all_unused_tables(this, &purge_tables); + mysql_mutex_unlock(&LOCK_table_share); + + while (auto table= purge_tables.pop_front()) + intern_close_table(table); +} |