On Mon, Jan 29, 2024 at 4:24 PM David Rowley <dgrowle...@gmail.com> wrote: > > On Tue, 30 Jan 2024 at 10:17, Melanie Plageman > <melanieplage...@gmail.com> wrote: > > Though logically the performance with 0001 and 0002 should be the same > > as master (no new non-inline function calls, no additional looping), > > I've done a bit of profiling anyway. I created a large multi-GB table, > > read it all into shared buffers (disabling the large sequential scan > > bulkread optimization), and did a sequential SELECT count(*) from the > > table. From the profiles below, you'll notice that master and the > > patch are basically the same. Actual percentages vary from run-to-run. > > Execution time is the same. > > Can you also run a test on a Seqscan with a filter that filters out > all tuples? There's less overhead in other parts of the executor with > such a query.
Yes, of course. Thank you so much for taking a look! While I was at it, I changed the table schema to be entirely composed of INT type columns and regenerated the data. Note that, both in this example and my previous example, I ensured that the table was vacuumed beforehand (and autovacuum disabled for the table) so there wasn't any on-access pruning happening (heapgetpage() does that in pagemode). This is the schema CREATE TABLE foo(id INT, a INT, b INT, c INT, d INT, e INT, f INT, g INT) with (autovacuum_enabled=false); I added 46000000 rows to the table, making it 2.6 GB. Shared buffers is double that. Before profiling, I did a SELECT * from the table with the large sequential scan bulkread optimization disabled. Then I vacuumed the table. Finally, I turned up parallel_setup_cost high enough to disable query parallelism. The query I profiled was: SELECT * FROM foo WHERE id = 0; With the data I generated, 0 rows match that condition. Profiles below. Execution time essentially the same. patch: 17.08% postgres postgres [.] ExecInterpExpr 11.17% postgres postgres [.] tts_buffer_heap_getsomeattrs 10.64% postgres postgres [.] ExecStoreBufferHeapTuple 9.82% postgres postgres [.] heap_getnextslot 9.13% postgres postgres [.] heapgettup_pagemode 8.98% postgres postgres [.] heapbuildvis 5.40% postgres postgres [.] HeapCheckForSerializableConflictOut 5.16% postgres postgres [.] SeqNext master: 17.89% postgres postgres [.] ExecInterpExpr 12.28% postgres postgres [.] tts_buffer_heap_getsomeattrs 10.54% postgres postgres [.] ExecStoreBufferHeapTuple 10.11% postgres postgres [.] heapgettup_pagemode 8.52% postgres postgres [.] heapgetpage 8.28% postgres postgres [.] heap_getnextslot 5.00% postgres postgres [.] HeapCheckForSerializableConflictOut 4.71% postgres postgres [.] SeqNext - Melanie
