Re: Bitmap Heap Scan taking ~60x as long for table when queried as partition

Stephen Froehlich wrote:
> Some of the partition scans are quick (those with nothing to return),
> but my point is that the scan PER TABLE is significantly slower than if
> I call the hypertable than if I call the table directly.
> THIS SHOULDN'T BE THE CASE. Most tables are scanned quickly and return nothing.
>
> There IS a combined index on client_ip_md5, start_time ... its my primary key for all of these tables.
>
> Also, the scans are typically parallelized (go back in the thread to the original excerpt),
> the only reason why not this time is that the server was busy with a backup.
> Its still much slower when calling the hypertable than the table directly.
> The parallelization is usually my first clue that an index scan is not being
> used but instead a heap scan.

In your complete plan, scanning "raptor_global_bitrate_20171101_cmts1" took
only 382.247 microseconds as opposed to 24760.668 in your first e-mail.
Also the strange "loops=6" is not present.

So it is hard to say what was going on there in the first place...

Often caching causes big differences in execution time.

Yours,
Laurenz Albe