| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
We as Arm Treasure Data are using Optimizer Hints with a monkey patch
(https://gist.github.com/kamipo/4c8539f0ce4acf85075cf5a6b0d9712e),
especially in order to use `MAX_EXECUTION_TIME` (refer #31129).
Example:
```ruby
class Job < ApplicationRecord
default_scope { optimizer_hints("MAX_EXECUTION_TIME(50000) NO_INDEX_MERGE(jobs)") }
end
```
Optimizer Hints is supported not only for MySQL but also for most
databases (PostgreSQL on RDS, Oracle, SQL Server, etc), it is really
helpful to turn heavy queries for large scale applications.
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
Initially, `TOP` was introduced to support `limit` for MSSQL database.
Unlike PostgreSQL/MySQL/SQLite, MSSQL does not have native `LIMIT`/`OFFSET` support.
The commit adding `TOP` is 1a246f71616cf246a75ef6cbdb56032e43d4e643.
However, it figured out that `TOP` implementation was weak and it's not sufficient
to also support `OFFSET`, then `TOP` was substituted with
`ROW_NUMBER()` subquery in be48ed3071fd6524d0145c4ad3faeb4aafe3eda3.
This is a well known trick in MSSQL -
https://stackoverflow.com/questions/2135418/equivalent-of-limit-and-offset-for-sql-server.
So now we don't need this `visit_Arel_Nodes_Top` at all.
It does nothing useful but also adds an extra space after `SELECT` when `LIMIT` is being
used for **any** database.
|
