Merge pull request #10571 from dasch/dasch/restore-explain-fix

Don't try to EXPLAIN select_db calls

3 files changed, 12 insertions, 1 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 117e527133..d27b11bddd 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,9 @@
 ## unreleased ##
 
+*   Make sure the `EXPLAIN` command is never triggered by a `select_db` call.
+
+    *Daniel Schierbeck*
+
 *   Revert changes on `pluck` that was ignoring the select clause when the relation already
     has one. This caused a regression since it changed the behavior in a stable release.
 
diff --git a/activerecord/lib/active_record/explain_subscriber.rb b/activerecord/lib/active_record/explain_subscriber.rb
index 859c8edfc5..1d861a57db 100644
--- a/activerecord/lib/active_record/explain_subscriber.rb
+++ b/activerecord/lib/active_record/explain_subscriber.rb
@@ -15,7 +15,7 @@ module ActiveRecord
     # On the other hand, we want to monitor the performance of our real database
     # queries, not the performance of the access to the query cache.
     IGNORED_PAYLOADS = %w(SCHEMA EXPLAIN CACHE)
-    EXPLAINED_SQLS = /\A\s*(select|update|delete|insert)/i
+    EXPLAINED_SQLS = /\A\s*(select|update|delete|insert)\b/i
     def ignore_payload?(payload)
       payload[:exception] || IGNORED_PAYLOADS.include?(payload[:name]) || payload[:sql] !~ EXPLAINED_SQLS
     end
diff --git a/activerecord/test/cases/explain_subscriber_test.rb b/activerecord/test/cases/explain_subscriber_test.rb
index 7b852a625d..0546e793fe 100644
--- a/activerecord/test/cases/explain_subscriber_test.rb
+++ b/activerecord/test/cases/explain_subscriber_test.rb
@@ -38,6 +38,13 @@ if ActiveRecord::Base.connection.supports_explain?
       end
     end
 
+    def test_collects_nothing_if_the_statement_is_only_partially_matched
+      with_queries([]) do |queries|
+        SUBSCRIBER.call(:name => 'SQL', :sql => 'select_db yo_mama')
+        assert queries.empty?
+      end
+    end
+
     def test_collects_nothing_if_unexplained_sqls
       with_queries([]) do |queries|
         SUBSCRIBER.call(:name => 'SQL', :sql => 'SHOW max_identifier_length')