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author | Jeremy Cole <jeremy@jcole.us> | 2012-07-13 09:42:48 -0700 |
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committer | Jeremy Cole <jeremy@jcole.us> | 2012-07-13 09:42:48 -0700 |
commit | e4ef90a9817fe0b6bb6cceaf9876c59e60eef7ac (patch) | |
tree | eeb5cf4391e993ab8dc9af67c16dbe0db78f1222 /activerecord/lib/active_record/connection_adapters | |
parent | e72d8768878efd13b817ad91a12f872f53efd809 (diff) | |
download | rails-e4ef90a9817fe0b6bb6cceaf9876c59e60eef7ac.tar.gz rails-e4ef90a9817fe0b6bb6cceaf9876c59e60eef7ac.tar.bz2 rails-e4ef90a9817fe0b6bb6cceaf9876c59e60eef7ac.zip |
Only use prepared statements when bind variables are present
Prepared statements (prepare/execute/close) were being used unnecessarily
when no bind variables were present, and disabling prepared statement using
prepared_statements:false was principally broken. While bind variables were
correctly substituted with prepared_statements:false, the prepared statement
interface was still used, costing an extra two round trips per query.
In addition to making this behavioral change, I also cleaned up the internals
of exec_stmt and exec_without_stmt so that they behave the same (calling log
and constructing the ActiveRecord::Result in the same way).
Moving the check for binds.empty? to exec_query also will mean that several
code paths explicitly calling exec_without_stmt could be cleaned up to once
again call exec_query instead. I have also left the check for binds.empty? in
exec_stmt, since it is not a private method and could be called directly with
an empty binds array. For the sake of clarity in this patch, I have not made
those changes.
= The previous behavior =
When issuing a Foo.find(1) with prepared_statements:true, the bind variable
is present in the prepared query, and execute shows a value passed:
Connect root@localhost on rails_test
Query SET SQL_AUTO_IS_NULL=0
Statistics
Query SHOW FULL FIELDS FROM `foos`
Query SHOW TABLES LIKE 'foos'
Query SHOW CREATE TABLE `foos`
Prepare SELECT `foos`.* FROM `foos` WHERE `foos`.`id` = ? LIMIT 1
Execute SELECT `foos`.* FROM `foos` WHERE `foos`.`id` = 1 LIMIT 1
Close stmt
Quit
When issuing a Foo.find(1) with prepared_statements:false, the bind variable
has already been removed and substituted with the value, but the prepared
statement interface is used anyway:
Connect root@localhost on rails_test
Query SET SQL_AUTO_IS_NULL=0
Statistics
Query SHOW FULL FIELDS FROM `foos`
Query SHOW TABLES LIKE 'foos'
Query SHOW CREATE TABLE `foos`
Prepare SELECT `foos`.* FROM `foos` WHERE `foos`.`id` = 1 LIMIT 1
Execute SELECT `foos`.* FROM `foos` WHERE `foos`.`id` = 1 LIMIT 1
Close stmt
Quit
= With this patch applied =
When issuing a Foo.find(1) with prepared_statements:true, the bind variable
is present in the prepared query, and execute shows a value passed:
Connect root@localhost on rails_test
Query SET SQL_AUTO_IS_NULL=0
Statistics
Query SHOW FULL FIELDS FROM `foos`
Query SHOW TABLES LIKE 'foos'
Query SHOW CREATE TABLE `foos`
Prepare SELECT `foos`.* FROM `foos` WHERE `foos`.`id` = ? LIMIT 1
Execute SELECT `foos`.* FROM `foos` WHERE `foos`.`id` = 1 LIMIT 1
Close stmt
Quit
When issuing a Foo.find(1) with prepared_statements:false, the bind variable
has been removed and substituted with the value, and the query interface is
used instead of the prepared statement interface:
Connect root@localhost on rails_test
Query SET SQL_AUTO_IS_NULL=0
Statistics
Query SHOW FULL FIELDS FROM `foos`
Query SHOW TABLES LIKE 'foos'
Query SHOW CREATE TABLE `foos`
Query SELECT `foos`.* FROM `foos` WHERE `foos`.`id` = 1 LIMIT 1
Quit
Diffstat (limited to 'activerecord/lib/active_record/connection_adapters')
-rw-r--r-- | activerecord/lib/active_record/connection_adapters/mysql_adapter.rb | 74 |
1 files changed, 40 insertions, 34 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb index f092edecda..2258ed9a21 100644 --- a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb +++ b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb @@ -282,10 +282,14 @@ module ActiveRecord end def exec_query(sql, name = 'SQL', binds = []) - log(sql, name, binds) do - exec_stmt(sql, name, binds) do |cols, stmt| - ActiveRecord::Result.new(cols, stmt.to_a) if cols - end + # If the configuration sets prepared_statements:false, binds will + # always be empty, since the bind variables will have been already + # substituted and removed from binds by BindVisitor, so this will + # effectively disable prepared statement usage completely. + if binds.empty? + exec_without_stmt(sql, name) + else + exec_stmt(sql, name, binds) end end @@ -342,41 +346,43 @@ module ActiveRecord def exec_stmt(sql, name, binds) cache = {} - if binds.empty? - stmt = @connection.prepare(sql) - else - cache = @statements[sql] ||= { - :stmt => @connection.prepare(sql) - } - stmt = cache[:stmt] - end + log(sql, name, binds) do + if binds.empty? + stmt = @connection.prepare(sql) + else + cache = @statements[sql] ||= { + :stmt => @connection.prepare(sql) + } + stmt = cache[:stmt] + end - begin - stmt.execute(*binds.map { |col, val| type_cast(val, col) }) - rescue Mysql::Error => e - # Older versions of MySQL leave the prepared statement in a bad - # place when an error occurs. To support older mysql versions, we - # need to close the statement and delete the statement from the - # cache. - stmt.close - @statements.delete sql - raise e - end + begin + stmt.execute(*binds.map { |col, val| type_cast(val, col) }) + rescue Mysql::Error => e + # Older versions of MySQL leave the prepared statement in a bad + # place when an error occurs. To support older mysql versions, we + # need to close the statement and delete the statement from the + # cache. + stmt.close + @statements.delete sql + raise e + end - cols = nil - if metadata = stmt.result_metadata - cols = cache[:cols] ||= metadata.fetch_fields.map { |field| - field.name - } - end + cols = nil + if metadata = stmt.result_metadata + cols = cache[:cols] ||= metadata.fetch_fields.map { |field| + field.name + } + end - result = yield [cols, stmt] + result = ActiveRecord::Result.new(cols, stmt.to_a) - stmt.result_metadata.free if cols - stmt.free_result - stmt.close if binds.empty? + stmt.result_metadata.free if cols + stmt.free_result + stmt.close if binds.empty? - result + result + end end def connect |