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MDEV-16849 Extending indexed VARCHAR column should be instantaneous

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Analysis:
========
Increasing the length of the indexed varchar column is not an instant operation for
innodb.

Fix:
===
- Introduce the new handler flag 'Alter_inplace_info::ALTER_COLUMN_INDEX_LENGTH' to
indicate the index length differs due to change of column length changes.

- InnoDB makes the ALTER_COLUMN_INDEX_LENGTH flag as instant operation.

This is a port of Mysql fix.

    commit 913071c0b16cc03e703308250d795bc381627e37
    Author: Nisha Gopalakrishnan <nisha.gopalakrishnan@oracle.com>
    Date:   Wed May 30 14:54:46 2018 +0530

        BUG#26848813: INDEXED COLUMN CAN'T BE CHANGED FROM VARCHAR(15)
                      TO VARCHAR(40) INSTANTANEOUSLY
This commit is contained in:
Thirunarayanan Balathandayuthapani
2019-01-30 15:32:51 +05:30
parent 97930df13c
commit b8aef87221
5 changed files with 834 additions and 12 deletions
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41
sql/sql_table.cc
View File

@ -6303,7 +6303,7 @@ static bool fill_alter_inplace_info(THD *thd,
bool varchar,
Alter_inplace_info *ha_alter_info)
{
Field **f_ptr, *field;
Field **f_ptr, *field, *old_field;
List_iterator_fast<Create_field> new_field_it;
Create_field *new_field;
KEY_PART_INFO *key_part, *new_part;
@ -6629,6 +6629,7 @@ static bool fill_alter_inplace_info(THD *thd,
Go through keys and check if the original ones are compatible
with new table.
*/
uint old_field_len= 0;
KEY *table_key;
KEY *table_key_end= table->key_info + table->s->keys;
KEY *new_key;
@ -6693,17 +6694,35 @@ static bool fill_alter_inplace_info(THD *thd,
key_part < end;
key_part++, new_part++)
{
/*
Key definition has changed if we are using a different field or
if the used key part length is different. It makes sense to
check lengths first as in case when fields differ it is likely
that lengths differ too and checking fields is more expensive
in general case.
*/
if (key_part->length != new_part->length)
goto index_changed;
new_field= get_field_by_index(alter_info, new_part->fieldnr);
old_field= table->field[key_part->fieldnr - 1];
/*
If there is a change in index length due to column expansion
like varchar(X) changed to varchar(X + N) and has a compatible
packed data representation, we mark it for fast/INPLACE change
in index definition. InnoDB supports INPLACE for this cases
Key definition has changed if we are using a different field or
if the user key part length is different.
*/
old_field_len= old_field->pack_length();
if (old_field->type() == MYSQL_TYPE_VARCHAR)
{
old_field_len= (old_field->pack_length()
- ((Field_varstring*) old_field)->length_bytes);
}
if (key_part->length == old_field_len &&
key_part->length < new_part->length &&
(key_part->field->is_equal((Create_field*) new_field)
== IS_EQUAL_PACK_LENGTH))
{
ha_alter_info->handler_flags |=
Alter_inplace_info::ALTER_COLUMN_INDEX_LENGTH;
}
else if (key_part->length != new_part->length)
goto index_changed;
/*
For prefix keys KEY_PART_INFO::field points to cloned Field