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EXPLAIN DELETE for MariaDB
- Backported the code to 10.0-base - Removed incorrect assert
This commit is contained in:
Sergey Petrunya
parent
a555ceb2fb
commit
18fec5128b
13 changed files with 551 additions and 84 deletions
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@ -40,6 +40,129 @@
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#include "records.h" // init_read_record,
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#include "sql_derived.h" // mysql_handle_list_of_derived
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// end_read_record
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/*
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@brief
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Print query plan of a single-table DELETE command
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@detail
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This function is used by EXPLAIN DELETE and by SHOW EXPLAIN when it is
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invoked on a running DELETE statement.
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*/
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int Delete_plan::print_explain(select_result_sink *output, uint8 explain_flags,
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bool *printed_anything)
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{
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if (deleting_all_rows || impossible_where)
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{
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const char *msg= deleting_all_rows? "Deleting all rows": "Impossible where";
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if (print_explain_message_line(output, explain_flags, 1/*select number*/,
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"SIMPLE", msg))
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{
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return 1;
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}
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*printed_anything= true;
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return 0;
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}
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select_lex->set_explain_type(FALSE);
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/*
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Print an EXPLAIN line. We dont have join, so we can't directly use
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JOIN::print_explain.
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We do have a SELECT_LEX (TODO but how is it useful? it has select_type..
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and that's it?)
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*/
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enum join_type jtype;
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if (select && select->quick)
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{
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int quick_type= select->quick->get_type();
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if ((quick_type == QUICK_SELECT_I::QS_TYPE_INDEX_MERGE) ||
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(quick_type == QUICK_SELECT_I::QS_TYPE_INDEX_INTERSECT) ||
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(quick_type == QUICK_SELECT_I::QS_TYPE_ROR_INTERSECT) ||
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(quick_type == QUICK_SELECT_I::QS_TYPE_ROR_UNION))
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jtype= JT_INDEX_MERGE;
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else
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jtype= JT_RANGE;
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}
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else
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{
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if (index == MAX_KEY)
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jtype= JT_ALL;
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else
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jtype= JT_NEXT;
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}
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StringBuffer<128> possible_keys_line;
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make_possible_keys_line(table, possible_keys, &possible_keys_line);
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const char *key_name;
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const char *key_len;
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StringBuffer<128> key_str;
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StringBuffer<128> key_len_str;
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StringBuffer<128> extra_str;
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/* Calculate key_len */
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if (select && select->quick)
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{
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select->quick->add_keys_and_lengths(&key_str, &key_len_str);
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key_name= key_str.c_ptr();
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key_len= key_len_str.c_ptr();
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}
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else
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{
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key_name= (index == MAX_KEY)? NULL : table->key_info[index].name;
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key_len= NULL;
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}
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if (select && select->cond)
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extra_str.append(STRING_WITH_LEN("Using where"));
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if (select && select->quick &&
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select->quick->get_type() == QUICK_SELECT_I::QS_TYPE_RANGE)
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{
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explain_append_mrr_info((QUICK_RANGE_SELECT*)select->quick, &extra_str);
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}
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if (using_filesort)
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{
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if (extra_str.length() !=0)
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extra_str.append(STRING_WITH_LEN("; "));
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extra_str.append(STRING_WITH_LEN("Using filesort"));
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}
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/*
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Single-table DELETE commands do not do "Using temporary".
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"Using index condition" is also not possible (which is an unjustified limitation)
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*/
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print_explain_row(output, explain_flags,
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1, /* id */
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select_lex->type,
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table->pos_in_table_list->alias,
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// partitions,
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jtype,
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possible_keys_line.length()? possible_keys_line.c_ptr(): NULL,
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key_name,
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key_len,
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NULL, /* 'ref' is always NULL in single-table EXPLAIN DELETE */
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select ? select->records : table_rows,
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extra_str.c_ptr());
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*printed_anything= true;
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for (SELECT_LEX_UNIT *unit= select_lex->first_inner_unit();
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unit;
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unit= unit->next_unit())
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{
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if (unit->print_explain(output, explain_flags, printed_anything))
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return 1;
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}
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return 0;
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}
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/**
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Implement DELETE SQL word.
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@ -61,12 +184,16 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
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bool const_cond_result;
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ha_rows deleted= 0;
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bool reverse= FALSE;
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bool err= true;
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ORDER *order= (ORDER *) ((order_list && order_list->elements) ?
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order_list->first : NULL);
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uint usable_index= MAX_KEY;
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SELECT_LEX *select_lex= &thd->lex->select_lex;
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killed_state killed_status= NOT_KILLED;
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THD::enum_binlog_query_type query_type= THD::ROW_QUERY_TYPE;
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Delete_plan query_plan;
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query_plan.index= MAX_KEY;
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query_plan.using_filesort= FALSE;
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DBUG_ENTER("mysql_delete");
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if (open_and_lock_tables(thd, table_list, TRUE, 0))
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@ -90,6 +217,8 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
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}
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thd_proc_info(thd, "init");
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table->map=1;
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query_plan.select_lex= &thd->lex->select_lex;
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query_plan.table= table;
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if (mysql_prepare_delete(thd, table_list, &conds))
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DBUG_RETURN(TRUE);
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@ -163,6 +292,11 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
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table->file->info(HA_STATUS_VARIABLE | HA_STATUS_NO_LOCK);
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ha_rows const maybe_deleted= table->file->stats.records;
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DBUG_PRINT("debug", ("Trying to use delete_all_rows()"));
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query_plan.set_delete_all_rows(maybe_deleted);
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if (thd->lex->describe)
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goto exit_without_my_ok;
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if (!(error=table->file->ha_delete_all_rows()))
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{
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/*
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@ -187,7 +321,12 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
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Item::cond_result result;
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conds= remove_eq_conds(thd, conds, &result);
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if (result == Item::COND_FALSE) // Impossible where
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{
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limit= 0;
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query_plan.set_impossible_where();
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if (thd->lex->describe)
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goto exit_without_my_ok;
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}
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}
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#ifdef WITH_PARTITION_STORAGE_ENGINE
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@ -195,6 +334,7 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
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{
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free_underlaid_joins(thd, select_lex);
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// No matching record
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//psergey-explain-todo: No-partitions used EXPLAIN here..
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my_ok(thd, 0);
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DBUG_RETURN(0);
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}
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@ -211,6 +351,10 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
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DBUG_RETURN(TRUE);
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if ((select && select->check_quick(thd, safe_update, limit)) || !limit)
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{
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query_plan.set_impossible_where();
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if (thd->lex->describe)
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goto exit_without_my_ok;
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delete select;
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free_underlaid_joins(thd, select_lex);
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/*
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@ -243,26 +387,46 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
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if (order)
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{
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uint length= 0;
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SORT_FIELD *sortorder;
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ha_rows examined_rows;
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ha_rows found_rows;
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table->update_const_key_parts(conds);
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order= simple_remove_const(order, conds);
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bool need_sort;
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if (select && select->quick && select->quick->unique_key_range())
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{ // Single row select (always "ordered")
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need_sort= FALSE;
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usable_index= MAX_KEY;
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query_plan.using_filesort= FALSE;
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query_plan.index= MAX_KEY;
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}
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else
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usable_index= get_index_for_order(order, table, select, limit,
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&need_sort, &reverse);
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if (need_sort)
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query_plan.index= get_index_for_order(order, table, select, limit,
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&query_plan.using_filesort,
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&reverse);
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}
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query_plan.select= select;
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query_plan.possible_keys= table->quick_keys;
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query_plan.table_rows= table->file->stats.records;
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thd->lex->delete_plan= &query_plan;
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/*
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Ok, we have generated a query plan for the DELETE.
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- if we're running EXPLAIN DELETE, goto produce explain output
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- otherwise, execute the query plan
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*/
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if (thd->lex->describe)
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goto exit_without_my_ok;
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thd->apc_target.enable();
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DBUG_EXECUTE_IF("show_explain_probe_delete_exec_start",
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dbug_serve_apcs(thd, 1););
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if (query_plan.using_filesort)
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{
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ha_rows examined_rows;
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ha_rows found_rows;
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uint length= 0;
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SORT_FIELD *sortorder;
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{
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DBUG_ASSERT(usable_index == MAX_KEY);
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DBUG_ASSERT(query_plan.index == MAX_KEY);
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table->sort.io_cache= (IO_CACHE *) my_malloc(sizeof(IO_CACHE),
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MYF(MY_FAE | MY_ZEROFILL |
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MY_THREAD_SPECIFIC));
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@ -276,6 +440,7 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
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{
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delete select;
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free_underlaid_joins(thd, &thd->lex->select_lex);
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thd->apc_target.disable();
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DBUG_RETURN(TRUE);
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}
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thd->examined_row_count+= examined_rows;
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@ -294,19 +459,21 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
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{
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delete select;
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free_underlaid_joins(thd, select_lex);
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thd->apc_target.disable();
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DBUG_RETURN(TRUE);
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}
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if (usable_index == MAX_KEY || (select && select->quick))
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if (query_plan.index == MAX_KEY || (select && select->quick))
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{
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if (init_read_record(&info, thd, table, select, 1, 1, FALSE))
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{
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delete select;
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free_underlaid_joins(thd, select_lex);
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thd->apc_target.disable();
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DBUG_RETURN(TRUE);
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}
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}
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else
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init_read_record_idx(&info, thd, table, 1, usable_index, reverse);
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init_read_record_idx(&info, thd, table, 1, query_plan.index, reverse);
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init_ftfuncs(thd, select_lex, 1);
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thd_proc_info(thd, "updating");
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@ -398,6 +565,7 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
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if (options & OPTION_QUICK)
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(void) table->file->extra(HA_EXTRA_NORMAL);
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thd->apc_target.disable();
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cleanup:
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/*
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Invalidate the table in the query cache if something changed. This must
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@ -458,6 +626,29 @@ cleanup:
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DBUG_PRINT("info",("%ld records deleted",(long) deleted));
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}
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DBUG_RETURN(error >= 0 || thd->is_error());
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/* Special exits */
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exit_without_my_ok:
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thd->lex->delete_plan= &query_plan;
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select_send *result;
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bool printed_anything;
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if (!(result= new select_send()))
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return 1; /* purecov: inspected */
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List<Item> dummy; /* note: looked in 5.6 and they too use a dummy list like this */
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result->prepare(dummy, &thd->lex->unit);
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thd->send_explain_fields(result);
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int err2= thd->lex->print_explain(result, 0 /* explain flags*/, &printed_anything);
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if (err2)
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result->abort_result_set();
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else
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result->send_eof();
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delete select;
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free_underlaid_joins(thd, select_lex);
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//table->set_keyread(false);
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DBUG_RETURN((err || thd->is_error() || thd->killed) ? 1 : 0);
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}
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