Re: FW: Re: Query is running very slow......

On 5/25/17 2:26 PM, Dinesh Chandra 12108 wrote:
> Hi Tomas,
>
> Please find the below input for slow query.
>
> (a) something about the hardware it's running on
> RAM-->64 GB, CPU->40core
>
> (b) amounts of data in the tables / databases
> Database size :32GB
> -----------------
> Tables size
> -----------------
> Workflow.project : 8194 byte
> workflow.tool_performance :175 MB
> workflow.evidence_to_do :580 MB
>
> (c) EXPLAIN or even better EXPLAIN ANALYZE of the query
>
> "GroupAggregate (cost=16583736169.63..18157894828.18 rows=5920110 width=69)"
> " -> Sort (cost=16583736169.63..16714893857.43 rows=52463075120 width=69)"
> " Sort Key: tool_performance.project_id, project.project_name, tool_performance.step_id, (date_trunc('day'::text, tool_performance.insert_time)), tool_performance.user_id"
> " -> Nested Loop (cost=2.42..787115179.07 rows=52463075120 width=69)"
> " -> Seq Scan on evidence_to_do (cost=0.00..119443.95 rows=558296 width=0)"
> " Filter: (status_id = ANY ('{15100,15150,15200,15300,15400,15500}'::bigint[]))"
> " -> Materialize (cost=2.42..49843.24 rows=93970 width=69)"
> " -> Hash Join (cost=2.42..49373.39 rows=93970 width=69)"
> " Hash Cond: (tool_performance.project_id = project.project_id)"
> " -> Seq Scan on tool_performance (cost=0.00..48078.88 rows=93970 width=39)"
> " Filter: ((insert_time > '2017-05-01 00:00:00+05:30'::timestamp with time zone) AND (insert_time < '2017-05-02 00:00:00+05:30'::timestamp with time zone))"
> " -> Hash (cost=1.63..1.63 rows=63 width=38)"
> " -> Seq Scan on project (cost=0.00..1.63 rows=63 width=38)"
>

Are you sure this is the same query? The query you posted includes there
two join conditions:

evidence_to_do.project_id = tool_performance.project_id
evidence_to_do.project_id = project.project_id

But the plan only seems to enforce the equality between 'project' and
'tool_performance'. So when joining the evidence_to_do, it performs a
cartesian product, producing ~52B rows (estimated). That can't be fast.

regards

--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services