On Mon, Aug 6, 2018 at 4:11 PM Tom Lane <tgl@xxxxxxxxxxxxx> wrote:
Ken Tanzer <ken.tanzer@xxxxxxxxx> writes:
> Hi. I was recently troubleshooting a function, and realized it had
> incorrectly been declared as Immutable, when it should have been declared
> Stable. When I changed it to Stable, the query I was running ran
> dramatically faster. Digging into this a little more, this is what I found:
EXPLAIN VERBOSE might shed a bit more light. I suspect you're falling
foul of the rather arcane rules about whether a SQL function can be
inlined. (Although it seems like only the wrapper function would be
inline-able anyway, so I'm not sure why the penalty is that high.)
regards, tom lane
Thanks Tom. This was as talkative as I could get it. I do see the difference on the Output line, but I don't know how to interperet it.
spc=> EXPLAIN (ANALYZE,BUFFERS,VERBOSE) SELECT client_id,si_imm(client_id) FROM tbl_residence_own;
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------
Seq Scan on public.tbl_residence_own (cost=0.00..1990.02 rows=6977 width=8) (actual time=3.771..22665.604 rows=6983 loops=1)
Output: client_id, si_imm(client_id)
Buffers: shared hit=199814
Planning time: 0.156 ms
Execution time: 22677.333 ms
(5 rows)
spc=> EXPLAIN (ANALYZE,BUFFERS,VERBOSE) SELECT client_id,si_stable(client_id) FROM tbl_residence_own;
QUERY PLAN
------------------------------------------------------------------------------------------------------------------------------
Seq Scan on public.tbl_residence_own (cost=0.00..3734.27 rows=6977 width=8) (actual time=3.100..1302.888 rows=6983 loops=1)
Output: client_id, staff_inspector_stable(client_id, target_date())
Buffers: shared hit=60174
Planning time: 0.354 ms
Execution time: 1315.746 ms
(5 rows)Cheers,
Ken
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