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Diffstat (limited to 'sql/sql_cursor.cc')
| -rw-r--r-- | sql/sql_cursor.cc | 660 |
1 files changed, 660 insertions, 0 deletions
diff --git a/sql/sql_cursor.cc b/sql/sql_cursor.cc new file mode 100644 index 00000000000..e8da691ea18 --- /dev/null +++ b/sql/sql_cursor.cc @@ -0,0 +1,660 @@ +/* Copyright (C) 2005 MySQL AB & MySQL Finland AB & TCX DataKonsult AB + + 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; either version 2 of the License, or + (at your option) any later version. + + 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ +#ifdef USE_PRAGMA_IMPLEMENTATION +#pragma implementation /* gcc class implementation */ +#endif + +#include "mysql_priv.h" +#include "sql_cursor.h" +#include "sql_select.h" + +/**************************************************************************** + Declarations. +****************************************************************************/ + +/* + Sensitive_cursor -- a sensitive non-materialized server side + cursor An instance of this class cursor has its own runtime + state -- list of used items and memory root for runtime memory, + open and locked tables, change list for the changes of the + parsed tree. This state is freed when the cursor is closed. +*/ + +class Sensitive_cursor: public Server_side_cursor +{ + MEM_ROOT main_mem_root; + Query_arena *stmt_arena; + JOIN *join; + TABLE *open_tables; + MYSQL_LOCK *lock; + TABLE *derived_tables; + /* List of items created during execution */ + query_id_t query_id; + struct Engine_info + { + const handlerton *ht; + void *read_view; + }; + Engine_info ht_info[MAX_HA]; + Item_change_list change_list; + my_bool close_at_commit; + THR_LOCK_OWNER lock_id; +private: + /* bzero cursor state in THD */ + void reset_thd(THD *thd); +public: + Sensitive_cursor(THD *thd, select_result *result_arg); + + THR_LOCK_OWNER *get_lock_id() { return &lock_id; } + /* Save THD state into cursor */ + void post_open(THD *thd); + + virtual bool is_open() const { return join != 0; } + virtual int open(JOIN *join); + virtual void fetch(ulong num_rows); + virtual void close(); + virtual ~Sensitive_cursor(); +}; + + +/* + Materialized_cursor -- an insensitive materialized server-side + cursor. The result set of this cursor is saved in a temporary + table at open. The cursor itself is simply an interface for the + handler of the temporary table. +*/ + +class Materialized_cursor: public Server_side_cursor +{ + MEM_ROOT main_mem_root; + /* A fake unit to supply to select_send when fetching */ + SELECT_LEX_UNIT fake_unit; + TABLE *table; + List<Item> item_list; + ulong fetch_limit; + ulong fetch_count; +public: + Materialized_cursor(select_result *result, TABLE *table); + + virtual bool is_open() const { return table != 0; } + virtual int open(JOIN *join __attribute__((unused))); + virtual void fetch(ulong num_rows); + virtual void close(); + virtual ~Materialized_cursor(); +}; + + +/* + Select_materialize -- a mediator between a cursor query and the + protocol. In case we were not able to open a non-materialzed + cursor, it creates an internal temporary HEAP table, and insert + all rows into it. When the table reaches max_heap_table_size, + it's converted to a MyISAM table. Later this table is used to + create a Materialized_cursor. +*/ + +class Select_materialize: public select_union +{ + select_result *result; /* the result object of the caller (PS or SP) */ +public: + Select_materialize(select_result *result_arg) :result(result_arg) {} + virtual bool send_fields(List<Item> &list, uint flags); +}; + + +/**************************************************************************/ + +/* + Attempt to open a materialized or non-materialized cursor. + + SYNOPSIS + mysql_open_cursor() + thd thread handle + flags [in] create a materialized cursor or not + result [in] result class of the caller used as a destination + for the rows fetched from the cursor + pcursor [out] a pointer to store a pointer to cursor in + + RETURN VALUE + 0 the query has been successfully executed; in this + case pcursor may or may not contain + a pointer to an open cursor. + non-zero an error, 'pcursor' has been left intact. +*/ + +int mysql_open_cursor(THD *thd, uint flags, select_result *result, + Server_side_cursor **pcursor) +{ + Sensitive_cursor *sensitive_cursor; + select_result *save_result; + Select_materialize *result_materialize; + LEX *lex= thd->lex; + int rc; + + /* + The lifetime of the sensitive cursor is the same or less as the + lifetime of the runtime memory of the statement it's opened for. + */ + if (! (result_materialize= new (thd->mem_root) Select_materialize(result))) + return 1; + + if (! (sensitive_cursor= new (thd->mem_root) Sensitive_cursor(thd, result))) + { + delete result; + return 1; + } + + save_result= lex->result; + + lex->result= result_materialize; + if (! (flags & (uint) ALWAYS_MATERIALIZED_CURSOR)) + { + thd->lock_id= sensitive_cursor->get_lock_id(); + thd->cursor= sensitive_cursor; + } + + rc= mysql_execute_command(thd); + + lex->result= save_result; + thd->lock_id= &thd->main_lock_id; + thd->cursor= 0; + + /* + Possible options here: + - a sensitive cursor is open. In this case rc is 0 and + result_materialize->table is NULL, or + - a materialized cursor is open. In this case rc is 0 and + result_materialize->table is not NULL + - an error occured during materializaton. + result_materialize->table is not NULL, but rc != 0 + - successful completion of mysql_execute_command without + a cursor: rc is 0, result_materialize->table is NULL, + sensitive_cursor is not open. + This is possible if some command writes directly to the + network, bypassing select_result mechanism. An example of + such command is SHOW VARIABLES or SHOW STATUS. + */ + if (rc) + goto err_open; + + if (sensitive_cursor->is_open()) + { + DBUG_ASSERT(!result_materialize->table); + /* + It's safer if we grab THD state after mysql_execute_command + is finished and not in Sensitive_cursor::open(), because + currently the call to Sensitive_cursor::open is buried deep + in JOIN::exec of the top level join. + */ + sensitive_cursor->post_open(thd); + *pcursor= sensitive_cursor; + goto end; + } + else if (result_materialize->table) + { + Materialized_cursor *materialized_cursor; + TABLE *table= result_materialize->table; + MEM_ROOT *mem_root= &table->mem_root; + + if (!(materialized_cursor= new (mem_root) + Materialized_cursor(result, table))) + { + rc= 1; + goto err_open; + } + + if ((rc= materialized_cursor->open(0))) + { + delete materialized_cursor; + goto err_open; + } + + *pcursor= materialized_cursor; + thd->stmt_arena->cleanup_stmt(); + goto end; + } + +err_open: + DBUG_ASSERT(! (sensitive_cursor && sensitive_cursor->is_open())); + delete sensitive_cursor; + if (result_materialize->table) + free_tmp_table(thd, result_materialize->table); +end: + delete result_materialize; + return rc; +} + +/**************************************************************************** + Server_side_cursor +****************************************************************************/ + +Server_side_cursor::~Server_side_cursor() +{ +} + + +void Server_side_cursor::operator delete(void *ptr, size_t size) +{ + Server_side_cursor *cursor= (Server_side_cursor*) ptr; + MEM_ROOT own_root= *cursor->mem_root; + + DBUG_ENTER("Server_side_cursor::operator delete"); + TRASH(ptr, size); + /* + If this cursor has never been opened mem_root is empty. Otherwise + mem_root points to the memory the cursor object was allocated in. + In this case it's important to call free_root last, and free a copy + instead of *mem_root to avoid writing into freed memory. + */ + free_root(&own_root, MYF(0)); + DBUG_VOID_RETURN; +} + +/**************************************************************************** + Sensitive_cursor +****************************************************************************/ + +Sensitive_cursor::Sensitive_cursor(THD *thd, select_result *result_arg) + :Server_side_cursor(&main_mem_root, result_arg), + stmt_arena(0), + join(0), + close_at_commit(FALSE) +{ + /* We will overwrite it at open anyway. */ + init_sql_alloc(&main_mem_root, ALLOC_ROOT_MIN_BLOCK_SIZE, 0); + thr_lock_owner_init(&lock_id, &thd->lock_info); + bzero((void*) ht_info, sizeof(ht_info)); +} + + +void +Sensitive_cursor::post_open(THD *thd) +{ + Engine_info *info; + /* + We need to save and reset thd->mem_root, otherwise it'll be + freed later in mysql_parse. + + We can't just change thd->mem_root here as we want to keep the + things that are already allocated in thd->mem_root for + Sensitive_cursor::fetch() + */ + *mem_root= *thd->mem_root; + stmt_arena= thd->stmt_arena; + state= stmt_arena->state; + /* Allocate a new memory root for thd */ + init_sql_alloc(thd->mem_root, + thd->variables.query_alloc_block_size, + thd->variables.query_prealloc_size); + + /* + Save tables and zero THD pointers to prevent table close in + close_thread_tables. + */ + derived_tables= thd->derived_tables; + open_tables= thd->open_tables; + lock= thd->lock; + query_id= thd->query_id; + free_list= thd->free_list; + change_list= thd->change_list; + reset_thd(thd); + /* Now we have an active cursor and can cause a deadlock */ + thd->lock_info.n_cursors++; + + close_at_commit= FALSE; /* reset in case we're reusing the cursor */ + info= &ht_info[0]; + for (handlerton **pht= thd->transaction.stmt.ht; *pht; pht++) + { + const handlerton *ht= *pht; + close_at_commit|= test(ht->flags & HTON_CLOSE_CURSORS_AT_COMMIT); + if (ht->create_cursor_read_view) + { + info->ht= ht; + info->read_view= (ht->create_cursor_read_view)(); + ++info; + } + } + /* + XXX: thd->locked_tables is not changed. + What problems can we have with it if cursor is open? + TODO: must be fixed because of the prelocked mode. + */ +} + + +void +Sensitive_cursor::reset_thd(THD *thd) +{ + thd->derived_tables= 0; + thd->open_tables= 0; + thd->lock= 0; + thd->free_list= 0; + thd->change_list.empty(); +} + + +int +Sensitive_cursor::open(JOIN *join_arg) +{ + join= join_arg; + THD *thd= join->thd; + /* First non-constant table */ + JOIN_TAB *join_tab= join->join_tab + join->const_tables; + DBUG_ENTER("Sensitive_cursor::open"); + + join->change_result(result); + /* + Send fields description to the client; server_status is sent + in 'EOF' packet, which follows send_fields(). + We don't simply use SEND_EOF flag of send_fields because we also + want to flush the network buffer, which is done only in a standalone + send_eof(). + */ + result->send_fields(*join->fields, Protocol::SEND_NUM_ROWS); + thd->server_status|= SERVER_STATUS_CURSOR_EXISTS; + result->send_eof(); + thd->server_status&= ~SERVER_STATUS_CURSOR_EXISTS; + + /* Prepare JOIN for reading rows. */ + join->tmp_table= 0; + join->join_tab[join->tables-1].next_select= setup_end_select_func(join); + join->send_records= 0; + join->fetch_limit= join->unit->offset_limit_cnt; + + /* Disable JOIN CACHE as it is not working with cursors yet */ + for (JOIN_TAB *tab= join_tab; + tab != join->join_tab + join->tables - 1; + tab++) + { + if (tab->next_select == sub_select_cache) + tab->next_select= sub_select; + } + + DBUG_ASSERT(join_tab->table->reginfo.not_exists_optimize == 0); + DBUG_ASSERT(join_tab->not_used_in_distinct == 0); + /* + null_row is set only if row not found and it's outer join: should never + happen for the first table in join_tab list + */ + DBUG_ASSERT(join_tab->table->null_row == 0); + DBUG_RETURN(0); +} + + +/* + SYNOPSIS + Sensitive_cursor::fetch() + num_rows fetch up to this number of rows (maybe less) + + DESCRIPTION + Fetch next num_rows rows from the cursor and send them to the client + + Precondition: + Sensitive_cursor is open + + RETURN VALUES: + none, this function will send OK to the clinet or set an error + message in THD +*/ + +void +Sensitive_cursor::fetch(ulong num_rows) +{ + THD *thd= join->thd; + JOIN_TAB *join_tab= join->join_tab + join->const_tables; + enum_nested_loop_state error= NESTED_LOOP_OK; + Query_arena backup_arena; + Engine_info *info; + DBUG_ENTER("Sensitive_cursor::fetch"); + DBUG_PRINT("enter",("rows: %lu", num_rows)); + + DBUG_ASSERT(thd->derived_tables == 0 && thd->open_tables == 0 && + thd->lock == 0); + + thd->derived_tables= derived_tables; + thd->open_tables= open_tables; + thd->lock= lock; + thd->query_id= query_id; + thd->change_list= change_list; + /* save references to memory allocated during fetch */ + thd->set_n_backup_active_arena(this, &backup_arena); + + for (info= ht_info; info->read_view ; info++) + (info->ht->set_cursor_read_view)(info->read_view); + + join->fetch_limit+= num_rows; + + error= sub_select(join, join_tab, 0); + if (error == NESTED_LOOP_OK || error == NESTED_LOOP_NO_MORE_ROWS) + error= sub_select(join,join_tab,1); + if (error == NESTED_LOOP_QUERY_LIMIT) + error= NESTED_LOOP_OK; /* select_limit used */ + if (error == NESTED_LOOP_CURSOR_LIMIT) + join->resume_nested_loop= TRUE; + +#ifdef USING_TRANSACTIONS + ha_release_temporary_latches(thd); +#endif + /* Grab free_list here to correctly free it in close */ + thd->restore_active_arena(this, &backup_arena); + + change_list= thd->change_list; + reset_thd(thd); + + for (info= ht_info; info->read_view; info++) + (info->ht->set_cursor_read_view)(0); + + if (error == NESTED_LOOP_CURSOR_LIMIT) + { + /* Fetch limit worked, possibly more rows are there */ + thd->server_status|= SERVER_STATUS_CURSOR_EXISTS; + result->send_eof(); + thd->server_status&= ~SERVER_STATUS_CURSOR_EXISTS; + } + else + { + close(); + if (error == NESTED_LOOP_OK) + { + thd->server_status|= SERVER_STATUS_LAST_ROW_SENT; + result->send_eof(); + thd->server_status&= ~SERVER_STATUS_LAST_ROW_SENT; + } + else if (error != NESTED_LOOP_KILLED) + my_message(ER_OUT_OF_RESOURCES, ER(ER_OUT_OF_RESOURCES), MYF(0)); + } + DBUG_VOID_RETURN; +} + + +void +Sensitive_cursor::close() +{ + THD *thd= join->thd; + DBUG_ENTER("Sensitive_cursor::close"); + + for (Engine_info *info= ht_info; info->read_view; info++) + { + (info->ht->close_cursor_read_view)(info->read_view); + info->read_view= 0; + info->ht= 0; + } + + thd->change_list= change_list; + { + /* + XXX: Another hack: we need to set THD state as if in a fetch to be + able to call stmt close. + */ + DBUG_ASSERT(lock || open_tables || derived_tables); + + TABLE *tmp_derived_tables= thd->derived_tables; + MYSQL_LOCK *tmp_lock= thd->lock; + + thd->open_tables= open_tables; + thd->derived_tables= derived_tables; + thd->lock= lock; + + /* Is expected to at least close tables and empty thd->change_list */ + stmt_arena->cleanup_stmt(); + + thd->open_tables= tmp_derived_tables; + thd->derived_tables= tmp_derived_tables; + thd->lock= tmp_lock; + } + thd->lock_info.n_cursors--; /* Decrease the number of active cursors */ + join= 0; + stmt_arena= 0; + free_items(); + change_list.empty(); + DBUG_VOID_RETURN; +} + + +Sensitive_cursor::~Sensitive_cursor() +{ + if (is_open()) + close(); +} + +/*************************************************************************** + Materialized_cursor +****************************************************************************/ + +Materialized_cursor::Materialized_cursor(select_result *result_arg, + TABLE *table_arg) + :Server_side_cursor(&table_arg->mem_root, result_arg), + table(table_arg), + fetch_limit(0), + fetch_count(0) +{ + fake_unit.init_query(); + fake_unit.thd= table->in_use; +} + + +int Materialized_cursor::open(JOIN *join __attribute__((unused))) +{ + THD *thd= fake_unit.thd; + int rc; + Query_arena backup_arena; + + thd->set_n_backup_active_arena(this, &backup_arena); + /* Create a list of fields and start sequential scan */ + rc= (table->fill_item_list(&item_list) || + result->prepare(item_list, &fake_unit) || + table->file->ha_rnd_init(TRUE)); + thd->restore_active_arena(this, &backup_arena); + return rc; +} + + +/* + Fetch up to the given number of rows from a materialized cursor. + + DESCRIPTION + Precondition: the cursor is open. + + If the cursor points after the last row, the fetch will automatically + close the cursor and not send any data (except the 'EOF' packet + with SERVER_STATUS_LAST_ROW_SENT). This is an extra round trip + and probably should be improved to return + SERVER_STATUS_LAST_ROW_SENT along with the last row. + + RETURN VALUE + none, in case of success the row is sent to the client, otherwise + an error message is set in THD +*/ + +void Materialized_cursor::fetch(ulong num_rows) +{ + THD *thd= table->in_use; + + int res= 0; + for (fetch_limit+= num_rows; fetch_count < fetch_limit; fetch_count++) + { + if ((res= table->file->rnd_next(table->record[0]))) + break; + /* Send data only if the read was successful. */ + result->send_data(item_list); + } + + switch (res) { + case 0: + thd->server_status|= SERVER_STATUS_CURSOR_EXISTS; + result->send_eof(); + thd->server_status&= ~SERVER_STATUS_CURSOR_EXISTS; + break; + case HA_ERR_END_OF_FILE: + thd->server_status|= SERVER_STATUS_LAST_ROW_SENT; + result->send_eof(); + thd->server_status&= ~SERVER_STATUS_LAST_ROW_SENT; + close(); + break; + default: + table->file->print_error(res, MYF(0)); + close(); + break; + } +} + + +void Materialized_cursor::close() +{ + /* Free item_list items */ + free_items(); + (void) table->file->ha_rnd_end(); + /* + We need to grab table->mem_root to prevent free_tmp_table from freeing: + the cursor object was allocated in this memory. + */ + main_mem_root= table->mem_root; + mem_root= &main_mem_root; + clear_alloc_root(&table->mem_root); + free_tmp_table(table->in_use, table); + table= 0; +} + + +Materialized_cursor::~Materialized_cursor() +{ + if (is_open()) + close(); +} + + +/*************************************************************************** + Select_materialize +****************************************************************************/ + +bool Select_materialize::send_fields(List<Item> &list, uint flags) +{ + bool rc; + DBUG_ASSERT(table == 0); + if (create_result_table(unit->thd, unit->get_unit_column_types(), + FALSE, thd->options | TMP_TABLE_ALL_COLUMNS, "")) + return TRUE; + /* + We can't simply supply SEND_EOF flag to send_fields, because send_fields + doesn't flush the network buffer. + */ + rc= result->send_fields(list, Protocol::SEND_NUM_ROWS); + thd->server_status|= SERVER_STATUS_CURSOR_EXISTS; + result->send_eof(); + thd->server_status&= ~SERVER_STATUS_CURSOR_EXISTS; + return rc; +} + |