diff options
Diffstat (limited to 'sql/opt_sum.cc')
| -rw-r--r-- | sql/opt_sum.cc | 113 |
1 files changed, 68 insertions, 45 deletions
diff --git a/sql/opt_sum.cc b/sql/opt_sum.cc index 87ef3af6e44..2bd757ee201 100644 --- a/sql/opt_sum.cc +++ b/sql/opt_sum.cc @@ -1,4 +1,4 @@ -/* Copyright (C) 2000-2003 MySQL AB +/* Copyright (c) 2000, 2010 Oracle and/or its affiliates. All rights reserved. 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 @@ -11,7 +11,7 @@ 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 */ + Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ /** @@ -96,7 +96,7 @@ static ulonglong get_exact_record_count(TABLE_LIST *tables) @param conds WHERE clause @note - This function is only called for queries with sum functions and no + This function is only called for queries with aggregate functions and no GROUP BY part. This means that the result set shall contain a single row only @@ -326,11 +326,7 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds) if (!error && reckey_in_range(0, &ref, item_field->field, conds, range_fl, prefix_len)) error= HA_ERR_KEY_NOT_FOUND; - if (table->key_read) - { - table->key_read= 0; - table->file->extra(HA_EXTRA_NO_KEYREAD); - } + table->disable_keyread(); table->file->ha_index_end(); if (error) { @@ -413,11 +409,7 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds) if (!error && reckey_in_range(1, &ref, item_field->field, conds, range_fl, prefix_len)) error= HA_ERR_KEY_NOT_FOUND; - if (table->key_read) - { - table->key_read=0; - table->file->extra(HA_EXTRA_NO_KEYREAD); - } + table->disable_keyread(); table->file->ha_index_end(); if (error) { @@ -567,31 +559,57 @@ bool simple_pred(Item_func *func_item, Item **args, bool *inv_order) /** Check whether a condition matches a key to get {MAX|MIN}(field):. - For the index specified by the keyinfo parameter, index that - contains field as its component (field_part), the function - checks whether the condition cond is a conjunction and all its - conjuncts referring to the columns of the same table as column - field are one of the following forms: - - f_i= const_i or const_i= f_i or f_i is null, - where f_i is part of the index - - field {<|<=|>=|>|=} const or const {<|<=|>=|>|=} field - - field between const1 and const2 - - @param[in] max_fl Set to 1 if we are optimising MAX() - @param[in,out] ref Reference to the structure we store the key - value - @param[in] keyinfo Reference to the key info - @param[in] field_part Pointer to the key part for the field - @param[in] cond WHERE condition - @param[in,out] key_part_used Map of matchings parts - @param[in,out] range_fl Says whether including key will be used - @param[out] prefix_len Length of common key part for the range - where MAX/MIN is searched for + For the index specified by the keyinfo parameter and an index that + contains the field as its component (field_part), the function + checks whether + + - the condition cond is a conjunction, + - all of its conjuncts refer to columns of the same table, and + - each conjunct is on one of the following forms: + - f_i = const_i or const_i = f_i or f_i IS NULL, + where f_i is part of the index + - field {<|<=|>=|>|=} const + - const {<|<=|>=|>|=} field + - field BETWEEN const_1 AND const_2 + + As a side-effect, the key value to be used for looking up the MIN/MAX value + is actually stored inside the Field object. An interesting feature is that + the function will find the most restrictive endpoint by over-eager + evaluation of the @c WHERE condition. It continually stores the current + endpoint inside the Field object. For a query such as + + @code + SELECT MIN(a) FROM t1 WHERE a > 3 AND a > 5; + @endcode + + the algorithm will recurse over the conjuction, storing first a 3 in the + field. In the next recursive invocation the expression a > 5 is evaluated + as 3 > 5 (Due to the dual nature of Field objects as value carriers and + field identifiers), which will obviously fail, leading to 5 being stored in + the Field object. + + @param[in] max_fl Set to true if we are optimizing MAX(), + false means we are optimizing %MIN() + @param[in, out] ref Reference to the structure where the function + stores the key value + @param[in] keyinfo Reference to the key info + @param[in] field_part Pointer to the key part for the field + @param[in] cond WHERE condition + @param[in,out] key_part_used Map of matchings parts. The function will output + the set of key parts actually being matched in + this set, yet it relies on the caller to + initialize the value to zero. This is due + to the fact that this value is passed + recursively. + @param[in,out] range_fl Says whether endpoints use strict greater/less + than. + @param[out] prefix_len Length of common key part for the range + where MAX/MIN is searched for @retval - 0 Index can't be used. + false Index can't be used. @retval - 1 We can use index to get MIN/MAX value + true We can use the index to get MIN/MAX value */ static bool matching_cond(bool max_fl, TABLE_REF *ref, KEY *keyinfo, @@ -628,17 +646,20 @@ static bool matching_cond(bool max_fl, TABLE_REF *ref, KEY *keyinfo, return 0; // Not operator, can't optimize bool eq_type= 0; // =, <=> or IS NULL + bool is_null_safe_eq= FALSE; // The operator is NULL safe, e.g. <=> bool noeq_type= 0; // < or > bool less_fl= 0; // < or <= - bool is_null= 0; - bool between= 0; + bool is_null= 0; // IS NULL + bool between= 0; // BETWEEN ... AND ... switch (((Item_func*) cond)->functype()) { case Item_func::ISNULL_FUNC: is_null= 1; /* fall through */ case Item_func::EQ_FUNC: + eq_type= TRUE; + break; case Item_func::EQUAL_FUNC: - eq_type= 1; + eq_type= is_null_safe_eq= TRUE; break; case Item_func::LT_FUNC: noeq_type= 1; /* fall through */ @@ -666,6 +687,10 @@ static bool matching_cond(bool max_fl, TABLE_REF *ref, KEY *keyinfo, if (!simple_pred((Item_func*) cond, args, &inv)) return 0; + if (!is_null_safe_eq && !is_null && + (args[1]->is_null() || (between && args[2]->is_null()))) + return FALSE; + if (inv && !eq_type) less_fl= 1-less_fl; // Convert '<' -> '>' (etc) @@ -716,15 +741,16 @@ static bool matching_cond(bool max_fl, TABLE_REF *ref, KEY *keyinfo, - field {>|>=} const, when searching for MIN */ - if (is_null) + if (is_null || (is_null_safe_eq && args[1]->is_null())) { part->field->set_null(); *key_ptr= (uchar) 1; } else { - store_val_in_field(part->field, args[between && max_fl ? 2 : 1], - CHECK_FIELD_IGNORE); + /* Update endpoints for MAX/MIN, see function comment. */ + Item *value= args[between && max_fl ? 2 : 1]; + store_val_in_field(part->field, value, CHECK_FIELD_IGNORE); if (part->null_bit) *key_ptr++= (uchar) test(part->field->is_null()); part->field->get_key_image(key_ptr, part->length, Field::itRAW); @@ -876,10 +902,7 @@ static bool find_key_for_maxmin(bool max_fl, TABLE_REF *ref, converted (for example to upper case) */ if (field->part_of_key.is_set(idx)) - { - table->key_read= 1; - table->file->extra(HA_EXTRA_KEYREAD); - } + table->enable_keyread(); return 1; } } |