use schema_cache

[noelr]

We had slow performance on inserts in rails 5 because column_definitions is called for each insert.

The call to column_definitions comes from query_requires_identity_insert? which calls identity_columns

Not sure what other consequences this patch has, please review. Also I'm unsure how to test.

[metaskills]

• What type of inserts?
• Were they simple model saves or SQL generated another way?
• Examples?

I ask because query_requires_identity_insert? is called in two places. First when using the base #execute vs #execute_insert which Rails should be calling internally now for model saves. Rails should also be passing pk as true to that method as well where the default is false because identity inserts do not normally happen. So I need to know a bit more and any info you can share helps.

Lastly, WRT testing. That is SUPER SUPER easy now with Docker based SQL Server on Linux. I'll update the docs with how to do that and post back.

[noelr]

First, Thank you for your fast reply and your great work on this gem!

The inserts are normal model create! and each create calls column_definitions (tested using a puts inside column_definitions)

I can run the tests but they fail, I'll look into that. But I'm unsure how to write a test that tests the new implementation of identity_columns

[noelr]

Example:

require 'benchmark'
Benchmark.measure do
  50.times do
    Book.create(name: "my book")
  end
end

=> @real=3.746845999998186
vs => @real=0.08944599999813363

[metaskills]

Yup, I remember spending some time on this shortly after Rails v5 release. Tho I don't remember the numbers like this. I might have been looking elsewhere. Will work on this very soon.

Test/Benchmark Diff

--- a/lib/active_record/connection_adapters/sqlserver/schema_statements.rb
+++ b/lib/active_record/connection_adapters/sqlserver/schema_statements.rb
@@ -513,7 +514,11 @@ module ActiveRecord
         end
 
         def identity_columns(table_name)
-          columns(table_name).select(&:is_identity?)
+          if $SCHEMCACHE
+            schema_cache.columns(table_name).select(&:is_identity?)
+          else
+            columns(table_name).select(&:is_identity?)
+          end
         end
--- a/test/cases/scratchpad_test_sqlserver.rb
+++ b/test/cases/scratchpad_test_sqlserver.rb
@@ -1,9 +1,13 @@
 require 'cases/helper_sqlserver'
+require 'models/book'
 
 class ScratchpadTestSQLServer < ActiveRecord::TestCase
 
   it 'helps debug things' do
-    #
+    require 'benchmark'
+    puts Benchmark.realtime { 1000.times { |n| Book.create(name: n) } }
+    $SCHEMCACHE = true
+    puts Benchmark.realtime { 1000.times { |n| Book.create(name: n) } }
   end
 
 end

Test/Benchmark Diff (output)

17.683182049018797
3.5568135359790176

[metaskills]

Closing for #574

[noelr]

Very nice - thank you! :)

[metaskills]

@noelr This work in in master. I hope to release that branch to v5.0.5 within the week. Cheers!

[noelr]

❤️