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author | Hiroyuki Morita <chiastolite.1980@gmail.com> | 2017-12-13 10:25:59 +0900 |
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committer | Hiroyuki Morita <chiastolite.1980@gmail.com> | 2017-12-13 11:14:46 +0900 |
commit | 3499d320d2e616a044b74db86fe4126de783174a (patch) | |
tree | d464bc1394d6296e00fbd086ee212953f21a8176 /activerecord/lib/active_record/touch_later.rb | |
parent | 9d43a84f73c1b3853a91d052a462ee60eccaf957 (diff) | |
download | rails-3499d320d2e616a044b74db86fe4126de783174a.tar.gz rails-3499d320d2e616a044b74db86fe4126de783174a.tar.bz2 rails-3499d320d2e616a044b74db86fe4126de783174a.zip |
Optimizing information_schema query for `foreign_keys`
Use CONSTRAINT_SCHEMA key for information_schema.referential_constraints.
See https://dev.mysql.com/doc/refman/5.7/en/information-schema-optimization.html.
```
> EXPLAIN SELECT fk.referenced_table_name AS 'to_table', fk.referenced_column_name AS 'primary_key', fk.column_name AS 'column', fk.constraint_name AS 'name', rc.update_rule AS 'on_update', rc.delete_rule AS 'on_delete' FROM information_schema.referential_constraints rc JOIN information_schema.key_column_usage fk USING (constraint_schema, constraint_name) WHERE fk.referenced_column_name IS NOT NULL AND fk.table_schema = 'activerecord_unittest' AND fk.table_name = 'fk_test_has_pk' AND rc.constraint_schema = 'activerecord_unittest' AND rc.table_name = 'fk_test_has_pk'\G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: rc
partitions: NULL
type: ALL
possible_keys: NULL
key: CONSTRAINT_SCHEMA,TABLE_NAME
key_len: NULL
ref: NULL
rows: NULL
filtered: NULL
Extra: Using where; Open_full_table; Scanned 0 databases
*************************** 2. row ***************************
id: 1
select_type: SIMPLE
table: fk
partitions: NULL
type: ALL
possible_keys: NULL
key: TABLE_SCHEMA,TABLE_NAME
key_len: NULL
ref: NULL
rows: NULL
filtered: NULL
Extra: Using where; Open_full_table; Scanned 0 databases; Using join buffer (Block Nested Loop)
2 rows in set, 1 warning (0.00 sec)
```
Diffstat (limited to 'activerecord/lib/active_record/touch_later.rb')
0 files changed, 0 insertions, 0 deletions