[Maria-developers] Rev 2739: MWL#17: Table elimination in file:///home/psergey/dev/maria-5.1-table-elim-r11/
At file:///home/psergey/dev/maria-5.1-table-elim-r11/ ------------------------------------------------------------ revno: 2739 revision-id: psergey@askmonty.org-20090820155102-5zvm1m6idmie9mmv parent: psergey@askmonty.org-20090819120659-0ndd6mqxeetgee2n committer: Sergey Petrunya <psergey@askmonty.org> branch nick: maria-5.1-table-elim-r11 timestamp: Thu 2009-08-20 17:51:02 +0200 message: MWL#17: Table elimination - Multiple-equality handling === modified file 'sql/item_cmpfunc.h' --- a/sql/item_cmpfunc.h 2008-12-12 11:13:11 +0000 +++ b/sql/item_cmpfunc.h 2009-08-20 15:51:02 +0000 @@ -1578,6 +1578,7 @@ uint members(); bool contains(Field *field); Item_field* get_first() { return fields.head(); } + uint n_fields() { return fields.elements; } void merge(Item_equal *item); void update_const(); enum Functype functype() const { return MULT_EQUAL_FUNC; } === modified file 'sql/opt_table_elimination.cc' --- a/sql/opt_table_elimination.cc 2009-08-19 12:06:59 +0000 +++ b/sql/opt_table_elimination.cc 2009-08-20 15:51:02 +0000 @@ -175,7 +175,10 @@ field_index */ Field_value *next_table_field; - uint bitmap_offset; /* Offset of our part of the bitmap */ + /* + Offset of our part of the bitmap psergey-todo: better comment! + */ + uint bitmap_offset; /* Field became known. Check out @@ -214,10 +217,6 @@ class Module_dep : public Sql_alloc { public: - enum { - MODULE_OUTER_JOIN - } type; /* Type of the object */ - virtual bool now_bound(Func_dep_analyzer *fda, Value_dep **bound_modules)=0; virtual ~Module_dep(){} /* @@ -232,8 +231,10 @@ /* - A "tbl.column= expr" equality dependency. tbl.column depends on fields - used in expr. + This represents either + - "tbl.column= expr" equality dependency, i.e. tbl.column depends on fields + used in the expression, or + - tbl1.col1=tbl2.col2=... multi-equality. */ class Equality_module : public Module_dep { @@ -241,6 +242,8 @@ Field_value *field; Item *expression; + List<Field_value> *mult_equal_fields; + /* Used during condition analysis only, similar to KEYUSE::level */ uint level; bool now_bound(Func_dep_analyzer *fda, Value_dep **bound_values); @@ -331,7 +334,7 @@ Item* cond); static -void build_eq_mods_for_cond(Func_dep_analyzer *fda, Equality_module **fdeps, +void build_eq_mods_for_cond(Func_dep_analyzer *fda, Equality_module **eq_mod, uint *and_level, Item *cond); static void add_eq_mod(Func_dep_analyzer *fda, Equality_module **eq_mod, @@ -346,6 +349,9 @@ static Field_value *get_field_value(Func_dep_analyzer *fda, Field *field); static void mark_as_eliminated(JOIN *join, TABLE_LIST *tbl); +static void add_eq_mod2(Func_dep_analyzer *fda, Equality_module **eq_mod, + uint and_level, Field_value *field_val, Item *right, + List<Field_value>* mult_equal_fields); #ifndef DBUG_OFF @@ -360,7 +366,7 @@ SYNOPSIS build_eq_mods_for_cond() fda Table elimination context - fdeps INOUT Put produced equality conditions here + eq_mod INOUT Put produced equality conditions here and_level INOUT AND-level (like in add_key_fields) cond Condition to process @@ -369,34 +375,34 @@ */ static -void build_eq_mods_for_cond(Func_dep_analyzer *fda, Equality_module **fdeps, +void build_eq_mods_for_cond(Func_dep_analyzer *fda, Equality_module **eq_mod, uint *and_level, Item *cond) { if (cond->type() == Item_func::COND_ITEM) { List_iterator_fast<Item> li(*((Item_cond*) cond)->argument_list()); - Equality_module *org_key_fields= *fdeps; + Equality_module *org_key_fields= *eq_mod; /* AND/OR */ if (((Item_cond*) cond)->functype() == Item_func::COND_AND_FUNC) { Item *item; while ((item=li++)) - build_eq_mods_for_cond(fda, fdeps, and_level, item); - for (; org_key_fields != *fdeps ; org_key_fields++) + build_eq_mods_for_cond(fda, eq_mod, and_level, item); + for (; org_key_fields != *eq_mod ; org_key_fields++) org_key_fields->level= *and_level; } else { Item *item; (*and_level)++; - build_eq_mods_for_cond(fda, fdeps, and_level, li++); + build_eq_mods_for_cond(fda, eq_mod, and_level, li++); while ((item=li++)) { - Equality_module *start_key_fields= *fdeps; + Equality_module *start_key_fields= *eq_mod; (*and_level)++; - build_eq_mods_for_cond(fda, fdeps, and_level, item); - *fdeps= merge_func_deps(org_key_fields, start_key_fields, *fdeps, + build_eq_mods_for_cond(fda, eq_mod, and_level, item); + *eq_mod= merge_func_deps(org_key_fields, start_key_fields, *eq_mod, ++(*and_level)); } } @@ -414,8 +420,8 @@ { if (cond_func->argument_count() == 2) { - add_eq_mod(fda, fdeps, *and_level, cond_func, args[0], args[1]); - add_eq_mod(fda, fdeps, *and_level, cond_func, args[1], args[0]); + add_eq_mod(fda, eq_mod, *and_level, cond_func, args[0], args[1]); + add_eq_mod(fda, eq_mod, *and_level, cond_func, args[1], args[0]); } break; } @@ -426,62 +432,72 @@ (fld= args[0]->real_item())->type() == Item::FIELD_ITEM && args[1]->eq(args[2], ((Item_field*)fld)->field->binary())) { - add_eq_mod(fda, fdeps, *and_level, cond_func, args[0], args[1]); - add_eq_mod(fda, fdeps, *and_level, cond_func, args[1], args[0]); + add_eq_mod(fda, eq_mod, *and_level, cond_func, args[0], args[1]); + add_eq_mod(fda, eq_mod, *and_level, cond_func, args[1], args[0]); } break; } case Item_func::EQ_FUNC: case Item_func::EQUAL_FUNC: { - add_eq_mod(fda, fdeps, *and_level, cond_func, args[0], args[1]); - add_eq_mod(fda, fdeps, *and_level, cond_func, args[1], args[0]); + add_eq_mod(fda, eq_mod, *and_level, cond_func, args[0], args[1]); + add_eq_mod(fda, eq_mod, *and_level, cond_func, args[1], args[0]); break; } case Item_func::ISNULL_FUNC: { Item *tmp=new Item_null; if (tmp) - add_eq_mod(fda, fdeps, *and_level, cond_func, args[0], args[1]); + add_eq_mod(fda, eq_mod, *and_level, cond_func, args[0], args[1]); break; } case Item_func::MULT_EQUAL_FUNC: { - Item_equal *item_equal= (Item_equal *) cond; - Item *const_item= item_equal->get_const(); + Item_equal *item_equal= (Item_equal*)cond; + // const item is 'item', field -> NULL. mult_equal_fields <-- an ordered + // list of + List<Field_value> *fvl; + if (!(fvl= new List<Field_value>)) + break; + Item_equal_iterator it(*item_equal); Item_field *item; - if (const_item) - { - /* - For each field field1 from item_equal consider the equality - field1=const_item as a condition allowing an index access of the table - with field1 by the keys value of field1. - */ - while ((item= it++)) - add_eq_mod(fda, fdeps, *and_level, cond_func, item, const_item); - } - else - { - /* - Consider all pairs of different fields included into item_equal. - For each of them (field1, field1) consider the equality - field1=field2 as a condition allowing an index access of the table - with field1 by the keys value of field2. - */ - Item_equal_iterator fi(*item_equal); - while ((item= fi++)) + Item *bound_item= item_equal->get_const(); + while ((item= it++)) + { + if ((item->used_tables() & fda->usable_tables)) { - Field *field= item->field; - Item_field *item2; - while ((item2= it++)) + Field_value *field_val; + if ((field_val= get_field_value(fda, item->field))) { - if (!field->eq(item2->field)) - add_eq_mod(fda, fdeps, *and_level, cond_func, item, item2); + List_iterator<Field_value> it2(*fvl); + Field_value *other_f; + uint field_val_ratio= field_val->field->table->tablenr*MAX_FIELDS + + field_val->field->field_index; + bool added= FALSE; + while ((other_f= it2++)) + { + uint other_f_ratio= other_f->field->table->tablenr*MAX_FIELDS + + other_f->field->field_index; + if (other_f_ratio > field_val_ratio) + { + *(it2.ref())= field_val; + it2.after(other_f); + added= TRUE; + break; + } + } + if (!added) + fvl->push_back(field_val); } - it.rewind(); + } + else + { + if (!bound_item) + bound_item= item; } } + add_eq_mod2(fda, eq_mod, *and_level, NULL, bound_item, fvl); break; } default: @@ -491,6 +507,39 @@ /* + The only requirement of this function is to order fields in some + deterministic way. +*/ + +int cmp_equal_fields(Item_field *field1, Item_field *field2, void *arg) +{ + int cmp= 0; + bool outer_ref= 0; + if (field2->used_tables() & OUTER_REF_TABLE_BIT) + { + outer_ref= 1; + cmp= -1; + } + if (field2->used_tables() & OUTER_REF_TABLE_BIT) + { + outer_ref= 1; + cmp++; + } + if (outer_ref) + return cmp; + cmp= (int)field2->field->table->tablenr - + (int)field1->field->table->tablenr; + if (cmp) + return cmp < 0 ? -1 : 1; + cmp= (int)field2->field->field_index - + (int)field1->field->field_index; + + return cmp < 0 ? -1 : (cmp ? 1 : 0); + +} + + +/* Perform an OR operation on two (adjacent) Equality_module arrays. SYNOPSIS @@ -540,9 +589,9 @@ Equality_module *end, uint and_level) { if (start == new_fields) - return start; // Impossible or + return start; // Impossible or if (new_fields == end) - return start; // No new fields, skip all + return start; // No new fields, skip all Equality_module *first_free=new_fields; @@ -551,40 +600,119 @@ for (Equality_module *old=start ; old != first_free ; old++) { /* - TODO: does it make sense to attempt to merging multiple-equalities? - A: YES. - (a=b=c) OR (a=b=d) produce "a=b". - QQ: - What to use for merging? Trivial N*M algorithm or pre-sort and then - merge ordered sequences? + Merge multiple-equalities: + A: YES. + (a=b=c) OR (a=b=d) produce "a=b". + + TODO: + sort by (table_ptr, column_index) + then run along the two and produce an intersection + + Q: What about constants? + a=b=3 OR a=b=5 -> a=b= (either 3 or 5) + + a=b OR a=b=5 -> a=b= (any constant) + A: keep the constant iff it is present in both sides and is the same. + + class Multi_equality + { + Item *const_item; + List<...) list; + }; + */ if (old->field == new_fields->field) { - if (!new_fields->expression->const_item()) - { - /* - If the value matches, we can use the key reference. - If not, we keep it until we have examined all new values - */ - if (old->expression->eq(new_fields->expression, old->field->field->binary())) - { - old->level= and_level; - } - } - else if (old->expression->eq_by_collation(new_fields->expression, - old->field->field->binary(), - old->field->field->charset())) - { - old->level= and_level; - } - else - { + if (!old->field) + { + /* + OR-ing two multiple equalities. We must compute an intersection of + used fields, and check the constants according to these rules: + + a=b=c=d OR a=c=e=f -> a=c (compute intersection) + a=const1 OR a=b -> (nothing) + a=const1 OR a=const1 -> a=const1 + a=const1 OR a=const2 -> (nothing) + + If we're performing an OR operation over multiple equalities, e.g. + + (a=b=c AND p=q) OR (a=b AND v=z) + + then we'll need to try combining each equality with each. ANDed + equalities are guaranteed to be disjoint, so we'll only get one + hit. + */ + if (old->expression && new_fields->expression && + old->expression->eq_by_collation(new_fields->expression, + old->mult_equal_fields->head()->field->binary(), + old->mult_equal_fields->head()->field->charset())) + { + /* Ok, keep */ + } + else + { + // no single constant/bound item. + old->expression= NULL; + } + + List <Field_value> *fv; + if (!(fv= new List<Field_value>)) + break; + + List_iterator<Field_value> it1(*old->mult_equal_fields); + List_iterator<Field_value> it2(*new_fields->mult_equal_fields); + Field_value *lfield= it1++; + Field_value *rfield= it2++; + // Merge + while (lfield && rfield) + { + if (lfield == rfield) + fv->push_back(lfield); + else + { + uint left_ratio= lfield->field->table->tablenr*MAX_FIELDS + + lfield->field->field_index; + uint right_ratio= rfield->field->table->tablenr*MAX_FIELDS + + rfield->field->field_index; + if (left_ratio < right_ratio) + lfield=it1++; + else + rfield=it2++; + } + } + + if (fv->elements + test(old->expression) > 1) + { + old->mult_equal_fields= fv; + old->level= and_level; + } + } + else if (!new_fields->expression->const_item()) + { + /* + If the value matches, we can use the key reference. + If not, we keep it until we have examined all new values + */ + if (old->expression->eq(new_fields->expression, + old->field->field->binary())) + { + old->level= and_level; + } + } + else if (old->expression->eq_by_collation(new_fields->expression, + old->field->field->binary(), + old->field->field->charset())) + { + old->level= and_level; + } + else + { /* The expressions are different. */ - if (old == --first_free) // If last item - break; - *old= *first_free; // Remove old value - old--; // Retry this value - } + if (old == --first_free) // If last item + break; + *old= *first_free; // Remove old value + old--; // Retry this value + } } } } @@ -596,10 +724,10 @@ for (Equality_module *old=start ; old != first_free ;) { if (old->level != and_level) - { // Not used in all levels + { // Not used in all levels if (old == --first_free) - break; - *old= *first_free; // Remove old value + break; + *old= *first_free; // Remove old value continue; } old++; @@ -659,33 +787,42 @@ return; } } - - if (*eq_mod == fda->equality_mods + fda->n_equality_mods_alloced) - { - /* - We've filled the entire equality_mods array. Replace it with a bigger - one. We do it somewhat inefficiently but it doesn't matter. - */ - Equality_module *new_arr; - if (!(new_arr= new Equality_module[fda->n_equality_mods_alloced *2])) - return; - fda->n_equality_mods_alloced *= 2; - for (int i= 0; i < *eq_mod - fda->equality_mods; i++) - new_arr[i]= fda->equality_mods[i]; - - fda->equality_mods= new_arr; - *eq_mod= new_arr + (*eq_mod - fda->equality_mods); - } - - if (!((*eq_mod)->field= get_field_value(fda, field))) + Field_value *field_val; + if ((field_val= get_field_value(fda, field))) + add_eq_mod2(fda, eq_mod, and_level, field_val, right, NULL); + } +} + + +/* Just add eq_mod w/o any checks */ +static void add_eq_mod2(Func_dep_analyzer *fda, Equality_module **eq_mod, + uint and_level, Field_value *field_val, Item *right, + List<Field_value>* mult_equal_fields) +{ + if (*eq_mod == fda->equality_mods + fda->n_equality_mods_alloced) + { + /* + We've filled the entire equality_mods array. Replace it with a bigger + one. We do it somewhat inefficiently but it doesn't matter. + */ + Equality_module *new_arr; + if (!(new_arr= new Equality_module[fda->n_equality_mods_alloced *2])) return; - (*eq_mod)->expression= right; - (*eq_mod)->level= and_level; - (*eq_mod)++; + fda->n_equality_mods_alloced *= 2; + for (int i= 0; i < *eq_mod - fda->equality_mods; i++) + new_arr[i]= fda->equality_mods[i]; + + fda->equality_mods= new_arr; + *eq_mod= new_arr + (*eq_mod - fda->equality_mods); } + + (*eq_mod)->field= field_val; + (*eq_mod)->expression= right; + (*eq_mod)->level= and_level; + (*eq_mod)->mult_equal_fields= mult_equal_fields; + (*eq_mod)++; } - /* Get a Table_value object for the given table, creating it if necessary. */ @@ -782,11 +919,15 @@ */ fda->equality_mods[expr_offset].unknown_args++; } + else + saw_other_tbl= TRUE; } Func_dep_analyzer *fda; /* Offset of the expression we're processing in the dependency bitmap */ - uint expr_offset; + uint expr_offset; + + bool saw_other_tbl; }; @@ -858,9 +999,21 @@ eq_mod++) { deps_recorder.expr_offset= eq_mod - fda->equality_mods; + deps_recorder.saw_other_tbl= FALSE; eq_mod->unknown_args= 0; + + /* Regular tbl.col=expr(tblX1.col1, tblY1.col2, ...) */ eq_mod->expression->walk(&Item::check_column_usage_processor, FALSE, (uchar*)&deps_recorder); + + if (!eq_mod->field) + { + if (eq_mod->unknown_args) + eq_mod->unknown_args= 1; + if (deps_recorder.saw_other_tbl) + eq_mod->unknown_args= 0; + } + if (!eq_mod->unknown_args) { eq_mod->next= bound_dep; @@ -1235,12 +1388,30 @@ Value_dep **bound_values) { /* For field=expr and we got to know the expr, so we know the field */ - if (!field->bound) - { - /* Mark as bound and add to the list */ - field->bound= TRUE; - field->next= *bound_values; - *bound_values= field; + if (mult_equal_fields) + { + List_iterator<Field_value> it(*mult_equal_fields); + Field_value *fv; + while ((fv= it++)) + { + if (!fv->bound) + { + /* Mark as bound and add to the list */ + fv->bound= TRUE; + fv->next= *bound_values; + *bound_values= fv; + } + } + } + else + { + if (!field->bound) + { + /* Mark as bound and add to the list */ + field->bound= TRUE; + field->next= *bound_values; + *bound_values= field; + } } return FALSE; } @@ -1313,11 +1484,19 @@ String str(buf, sizeof(buf), &my_charset_bin); str.length(0); eq_mod->expression->print(&str, QT_ORDINARY); - fprintf(DBUG_FILE, " equality%d: %s -> %s.%s\n", - eq_mod - fda->equality_mods, - str.c_ptr(), - eq_mod->field->table->table->alias, - eq_mod->field->field->field_name); + if (eq_mod->field) + { + fprintf(DBUG_FILE, " equality%d: %s -> %s.%s\n", + eq_mod - fda->equality_mods, + str.c_ptr(), + eq_mod->field->table->table->alias, + eq_mod->field->field->field_name); + } + else + { + fprintf(DBUG_FILE, " equality%d: multi-equality", + eq_mod - fda->equality_mods); + } } fprintf(DBUG_FILE,"\n");
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Sergey Petrunya