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author | Ryuta Kamizono <kamipo@gmail.com> | 2019-03-13 09:29:00 +0900 |
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committer | Ryuta Kamizono <kamipo@gmail.com> | 2019-03-16 18:44:55 +0900 |
commit | 97347d8c409f14b682dd9ec52ded3c869d0ba479 (patch) | |
tree | 7baf7114da2ed0e305663085778267b6a3f06cb7 /activerecord/lib/arel/visitors/ibm_db.rb | |
parent | 85984e50311b7138504abe1be9bbe99f96dde8ef (diff) | |
download | rails-97347d8c409f14b682dd9ec52ded3c869d0ba479.tar.gz rails-97347d8c409f14b682dd9ec52ded3c869d0ba479.tar.bz2 rails-97347d8c409f14b682dd9ec52ded3c869d0ba479.zip |
Support Optimizer Hints
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.
Diffstat (limited to 'activerecord/lib/arel/visitors/ibm_db.rb')
-rw-r--r-- | activerecord/lib/arel/visitors/ibm_db.rb | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/activerecord/lib/arel/visitors/ibm_db.rb b/activerecord/lib/arel/visitors/ibm_db.rb index 73166054da..0ffc0725f7 100644 --- a/activerecord/lib/arel/visitors/ibm_db.rb +++ b/activerecord/lib/arel/visitors/ibm_db.rb @@ -4,6 +4,14 @@ module Arel # :nodoc: all module Visitors class IBM_DB < Arel::Visitors::ToSql private + def visit_Arel_Nodes_SelectCore(o, collector) + collector = super + maybe_visit o.optimizer_hints, collector + end + + def visit_Arel_Nodes_OptimizerHints(o, collector) + collector << "/* <OPTGUIDELINES>#{sanitize_as_sql_comment(o).join}</OPTGUIDELINES> */" + end def visit_Arel_Nodes_Limit(o, collector) collector << "FETCH FIRST " @@ -16,6 +24,10 @@ module Arel # :nodoc: all collector = visit [o.left, o.right, 0, 1], collector collector << ")" end + + def collect_optimizer_hints(o, collector) + collector + end end end end |