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MDEV-7317: Make an index ignorable to the optimizer

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This feature adds the functionality of ignorability for indexes.
Indexes are not ignored be default.

To control index ignorability explicitly for a new index,
use IGNORE or NOT IGNORE as part of the index definition for
CREATE TABLE, CREATE INDEX, or ALTER TABLE.

Primary keys (explicit or implicit) cannot be made ignorable.

The table INFORMATION_SCHEMA.STATISTICS get a new column named IGNORED that
would store whether an index needs to be ignored or not.
This commit is contained in:
Varun Gupta
2021-02-25 19:59:51 +05:30
parent 71d30d01aa
commit f691d9865b
108 changed files with 2541 additions and 1422 deletions
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107
sql/sql_table.cc
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@ -4445,7 +4445,7 @@ without_overlaps_err:
}
create_info->period_info.unique_keys++;
}
key_info->is_ignored= key->key_create_info.is_ignored;
key_info++;
}
@ -7043,6 +7043,33 @@ Compare_keys compare_keys_but_name(const KEY *table_key, const KEY *new_key,
return result;
}
/**
Look-up KEY object by index name using case-insensitive comparison.
@param key_name Index name.
@param key_start Start of array of KEYs for table.
@param key_end End of array of KEYs for table.
@note Case-insensitive comparison is necessary to correctly
handle renaming of keys.
@retval non-NULL - pointer to KEY object for index found.
@retval NULL - no index with such name found (or it is marked
as renamed).
*/
static KEY *find_key_ci(const char *key_name, KEY *key_start, KEY *key_end)
{
for (KEY *key = key_start; key < key_end; key++)
{
if (!my_strcasecmp(system_charset_info, key_name, key->name.str))
return key;
}
return NULL;
}
/**
Compare original and new versions of a table and fill Alter_inplace_info
describing differences between those versions.
@ -7102,7 +7129,10 @@ static bool fill_alter_inplace_info(THD *thd, TABLE *table, bool varchar,
! (ha_alter_info->index_add_buffer=
(uint*) thd->alloc(sizeof(uint) *
alter_info->key_list.elements)) ||
ha_alter_info->rename_keys.reserve(ha_alter_info->index_add_count))
ha_alter_info->rename_keys.reserve(ha_alter_info->index_add_count) ||
! (ha_alter_info->index_altered_ignorability_buffer=
(KEY_PAIR*)thd->alloc(sizeof(KEY_PAIR) *
alter_info->alter_index_ignorability_list.elements)))
DBUG_RETURN(true);
/*
@ -7507,6 +7537,29 @@ static bool fill_alter_inplace_info(THD *thd, TABLE *table, bool varchar,
}
}
List_iterator<Alter_index_ignorability>
ignorability_index_it(alter_info->alter_index_ignorability_list);
Alter_index_ignorability *alter_index_ignorability;
while((alter_index_ignorability= ignorability_index_it++))
{
const char *name= alter_index_ignorability->name();
KEY *old_key, *new_key;
old_key= find_key_ci(name, table->key_info, table_key_end);
new_key= find_key_ci(name, ha_alter_info->key_info_buffer, new_key_end);
DBUG_ASSERT(old_key != NULL);
if (new_key == NULL)
{
my_error(ER_KEY_DOES_NOT_EXISTS, MYF(0), name, table->s->table_name.str);
DBUG_RETURN(true);
}
new_key->is_ignored= alter_index_ignorability->is_ignored();
ha_alter_info->handler_flags|= ALTER_RENAME_INDEX;
ha_alter_info->add_altered_index_ignorability(old_key, new_key);
}
/*
Sort index_add_buffer according to how key_info_buffer is sorted.
I.e. with primary keys first - see sort_keys().
@ -8341,6 +8394,17 @@ mysql_prepare_alter_table(THD *thd, TABLE *table,
/* New key definitions are added here */
List<Key> new_key_list;
List<Alter_rename_key> rename_key_list(alter_info->alter_rename_key_list);
/*
Create a deep copy of the list of visibility for indexes, as it will be
altered here.
*/
List<Alter_index_ignorability>
alter_index_ignorability_list(alter_info->alter_index_ignorability_list,
thd->mem_root);
list_copy_and_replace_each_value(alter_index_ignorability_list, thd->mem_root);
List_iterator<Alter_drop> drop_it(alter_info->drop_list);
List_iterator<Create_field> def_it(alter_info->create_list);
List_iterator<Alter_column> alter_it(alter_info->alter_list);
@ -8808,6 +8872,18 @@ mysql_prepare_alter_table(THD *thd, TABLE *table,
continue;
}
List_iterator<Alter_index_ignorability>
ignorability_index_it(alter_index_ignorability_list);
Alter_index_ignorability *index_ignorability;
while((index_ignorability= ignorability_index_it++))
{
const char* name= index_ignorability->name();
if (!my_strcasecmp(system_charset_info, key_name, name))
ignorability_index_it.remove();
}
/* If this index is to stay in the table check if it has to be renamed. */
List_iterator<Alter_rename_key> rename_key_it(rename_key_list);
Alter_rename_key *rename_key;
@ -8956,6 +9032,7 @@ mysql_prepare_alter_table(THD *thd, TABLE *table,
key_create_info.parser_name= *plugin_name(key_info->parser);
if (key_info->flags & HA_USES_COMMENT)
key_create_info.comment= key_info->comment;
key_create_info.is_ignored= key_info->is_ignored;
/*
We're refreshing an already existing index. Since the index is not
@ -8987,6 +9064,24 @@ mysql_prepare_alter_table(THD *thd, TABLE *table,
else
key_type= Key::MULTIPLE;
List_iterator<Alter_index_ignorability>
ignorability_index_it(alter_info->alter_index_ignorability_list);
Alter_index_ignorability *index_ignorability;
while((index_ignorability= ignorability_index_it++))
{
const char *name= index_ignorability->name();
if (!my_strcasecmp(system_charset_info, key_name, name))
{
if (table->s->primary_key <= MAX_KEY &&
table->key_info + table->s->primary_key == key_info)
{
my_error(ER_PK_INDEX_CANT_BE_IGNORED, MYF(0));
goto err;
}
key_create_info.is_ignored= index_ignorability->is_ignored();
}
}
tmp_name.str= key_name;
tmp_name.length= strlen(key_name);
/* We dont need LONG_UNIQUE_HASH_FIELD flag because it will be autogenerated */
@ -9181,6 +9276,14 @@ mysql_prepare_alter_table(THD *thd, TABLE *table,
goto err;
}
if (alter_index_ignorability_list.elements)
{
my_error(ER_KEY_DOES_NOT_EXISTS, MYF(0),
alter_index_ignorability_list.head()->name(),
table->s->table_name.str);
goto err;
}
if (!create_info->comment.str)
{
create_info->comment.str= table->s->comment.str;