Don't EXPLAIN the unexplainable in postgresql

[dlee]

Only run EXPLAIN for statements that are supported. Really fixes Issue #5430.

[rafaelfranca]

I think is better to add the no supported queries to this: https://github.com/dlee/rails/blob/4ff8fde2f0f7055f3b869593b3ee6f711255a073/activerecord/lib/active_record/explain_subscriber.rb#L20

[kennyj]

It seems that this is related to #6458 .

[dlee]

@rafaelfranca Ah, didn't even see that. What do you think about making it a whitelist instead of a blacklist? @kennyj adds a whitelist approach here: kennyj@4a25742

[rafaelfranca]

@dlee I prefer the whitelist too. Could you guys work on this one and ping me when finished?

[kennyj]

@dlee my approach is similar to your approach.
But I think supports of other adapter (mysql, sqlite...) is important.
And I also think queries (Thread.current[:available_queries_for_explain]) shouldn't be long. Thus I fixed it in the explain_subscriber.rb.
wdyt?

[dlee]

@kennyj Yeah, I think your whitelist approach is better. Would it make sense to take out the IGNORED_PAYLOADS and just use EXPLAINED_SQLS?

[kennyj]

I think we should use both IGNORED_PAYLOADS and EXPLAINED_SQLS. For example {CACHE, "select * from users where users.id = 1"}, this should be ignored.

[rafaelfranca]

👍 Thank you to take care of this one guys. Ping me when done

[dlee]

@kennyj Should we have a ACCEPTED_PAYLOADS instead of IGNORED_PAYLOADS? Or is the list of accepted payloads too hard to maintain?

[kennyj]

@dlee Sorry for keeping you waiting for this reply.

IMO, we should use IGNORED_PAYLOADS, because payloads usage is inconsistency.

for example, https://github.com/rails/rails/blob/master/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb#L406

I think too hard to maintain too.

[kennyj]

If you agree with me, I submit PR about 4a25742 .

[fxn]

Shouldn't that PRAGMA query be marked as SCHEMA?

[kennyj]

@fxn I agree with you. I'll send a PR that against it.

BTW, I investigated name's varietions when executing rake.
https://gist.github.com/3726395

[rafaelfranca]

@kennyj I think the PR is fine. Please send it

[kennyj]

@rafaelfranca I sent the PR.

[ddoherty03]

I don't see this in the current 3.2.x code. Any chance this will get pushed out to the active_record gem soon?

[rafaelfranca]

It was released on 3.2.9