Re: Query much slower on 9.6.5 than on 9.3.5

[Ron <ronljohnsonjr@xxxxxxxxx>]

On 4/5/19 3:43 AM, Rob Northcott wrote:

I’ve had a couple of customers complaining of slow searches and doing some testing last night it seems to be much slower on the live server than on my test setup.

It’s quite a messy query built up by the search code, with lots of joins and subqueries.

I’ve downloaded a backup of the customer’s live database to test, so I’m running the same query on the same data, just two different servers.

On the local test server (PSQL 9.3.5 running on an old Core2 Duo PC) it takes around 200ms to run the query.

On the live server (PSQL 9.6.5 on virtual server with 4 cores) it takes 20 seconds to run the same query.

 

Looking at the explain analyse, the two servers are using quite different optimisation plans, but I can’t find any differences in the settings.

 

Is there anything obvious I should look at that may be different between 9.3 and 9.6?

 

If not, would it help if I post the analyse output on here? (can we post attachments to the group or should it just be text in the email?)

 

Many thanks for any hints

I'll get the obvious first question out of the way, so that no one else has to ask: have you analyzed the 9.6 database?  If not, do that first.

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