Re: [GENERAL] testcase failing on git master / how to progress
On 18/03/2017 01:22, Adrian Klaver wrote: On 03/17/2017 06:07 PM, Martin F wrote: Hi, I just started last week to build postgresql from source. (So this may well be something I did wrong on my side) Do you really want to build the latest dev version? Yes, I want the latest, and I understand, that it may be unstable. this is not using the postgres in any production/development. Rather that I want to start exploring the postgres sources themself. -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
[GENERAL] testcase failing on git master / how to progress
Hi, I just started last week to build postgresql from source. (So this may well be something I did wrong on my side) I am on branch master Revision: f7819baa618c528f60e266874051563ecfe08207 Date: 17/03/2017 18:58:06 I did build with make clean distclean ./configure --prefix=/deploys/postgresql/inst/ --with-pgport=5433 --enable-debug CFLAGS="-ggdb -O0 -g3 -fno-omit-frame-pointer" make make install And I got a few tests failing. macaddr8 ... FAILED opr_sanity ... FAILED object_address ... FAILED If I build with ./configure --prefix=/deploys/postgresql/inst/ --with-pgport=5433 then all tests pass. So questions: - Can anyone else reproduce this? - How to establish if this is a problem with my build, or a bug in pg? (And if the latter, what next) one more note: make check has a problem on my system, but I (believe I) have worked around. I can see that "make check" sets PATH="/deploys/postgresql/postgresql/tmp_install/deploys/postgresql/inst/bin:$PATH" LD_LIBRARY_PATH="/deploys/postgresql/postgresql/tmp_install/deploys/postgresql/inst/lib" but this path does not exist, and therefore binaries are not found. I did install the build, and set the path (and ld-path) to include the install location, then run the tests. I have not found what causes this issue, but maybe it is the --prefix? uname -a FreeBSD bsd1 10.0-RELEASE FreeBSD 10.0-RELEASE #0 r260789: Fri Jan 17 01:46:25 UTC 2014 r...@snap.freebsd.org:/usr/obj/usr/src/sys/GENERIC i386 gmake --version GNU Make 4.1 Built for i386-portbld-freebsd10.0 cc --version FreeBSD clang version 3.3 (tags/RELEASE_33/final 183502) 20130610 Target: i386-unknown-freebsd10.0 Thread model: posix -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] odd optimizer result, index condition "is not null" on column defined as "not null"
On 03/03/2017 17:33, Tom Lane wrote: Martin F <p...@mfriebe.de> writes: The select with filter choose an IMHO better plan Index Only Scan using tbl_foo_date on public.tbl_foo But the bigger picture here, which would become more obvious if you were working with a non-toy amount of data, is that you're asking the planner to choose between two bad options. I agree "better" was the wrong term. "different" And yes they are both bad. And in fact after some more research, I think I found https://wiki.postgresql.org/wiki/Index-only_scans#What_types_of_queries_may_be_satisfied_by_an_index-only_scan.3F which explains why the aggregate-with-filter is potentially much worse (as it accesses more rows) Lets see, if I am closer to a correct understanding. Lets see if my following assumptions are (closer to being) correct: So the real missing feature here is the opposite of what I expected. select min(id) filter(where created_at >= '2017-01-15') from tbl_foo is NOT rewritten to select id from tbl_foo where created_at >= '2017-01-15' and id is not null order by id limit 1 That is the filter is currently not transformed to a where. On the other hand, looking at the explain of explain analyze verbose select min(id) filter(where created_at >= '2017-01-15') from tbl_foo; QUERY PLAN --- Aggregate (cost=13.28..13.29 rows=1 width=16) (actual time=0.799..0.804 rows=1 loops=1) Output: min(id) FILTER (WHERE (created_at >= '2017-01-15 00:00:00'::timestamp without time zone)) -> Index Only Scan using tbl_foo_id_date on public.tbl_foo (cost=0.14..13.00 rows=57 width=16) (actual time=0.024..0.437 rows=57 loops=1) Output: created_at, id Heap Fetches: 57 Planning time: 0.080 ms Execution time: 0.901 ms 57 heap fetches, so one for every row. It seems that min() does a heap fetch for every row, even if the value for that row is bigger than the current aggregated value. That is the heap fetch happens, even if the value's visibility does not matter / the value will be discarded anyway. (Of course that is because the function can not affect the scanners decision if a row is required or not) Are my above observation and conclusions correct, or am I missing something crucially (apart from that I am only looking at a tiny fraction of reality) If you are concerned about the performance of this specific query shape, what you actually want is an index on (id, created_at). That allows stopping at the first index entry satisfying the created_at condition, knowing that it must have the min id value that does so. Thanks indeed, taking in account the true nature of "index only", the above is a good idea. regards Martin -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] odd optimizer result, index condition "is not null" on column defined as "not null"
On 03/03/2017 17:33, Tom Lane wrote: Martin F <p...@mfriebe.de> writes: Index Cond: (tbl_foo.id IS NOT NULL) only "id" is the pk, and declared "not null". So why this index condition? You're right that we could observe that the NOT NULL is implied by a table constraint and drop it, but it seems unlikely to be worth the planner cycles to do so; the condition doesn't cost much at runtime. (Also, plans that depend on table constraints for correctness have added bookkeeping costs from tracking such dependency.) Thanks for the explanation. I looked at more example and yet found another case. The planer can choose an index, where the index has the same condition as (part of) the query conditions. I added the 2 indexes create index tbl_foo_ID_1 on tbl_foo using btree (id) where (id <>1); create index tbl_foo_ID_null on tbl_foo using btree (id) where (id is not null); and used the 2 queries (already transformed, so the first does not have the "not null") explain analyze verbose select id from tbl_foo where created_at >= '2017-01-15' and id <>1 order by id limit 1; explain analyze verbose select id from tbl_foo where created_at >= '2017-01-15' and id is not null order by id limit 1; both choose the index with the matching condition ... Index Scan using tbl_foo_id_1 ... Index Scan using tbl_foo_id_null The "<> 1" condition does not appear in the plan (as it is covered by the chosen index) But the "is not null condition is kept, why? Yes I understand, it makes probably little difference in the end, but I think it is somewhat curious. This also happens, if I change id to: id bigserial (that is make in null-able / yet the index remains filtered to none null only) explain analyze verbose select id from tbl_foo where created_at >= '2017-01-15' and id <>1 order by id limit 1; QUERY PLAN - Limit (cost=0.14..0.45 rows=1 width=8) (actual time=0.039..0.044 rows=1 loops=1) Output: id -> Index Scan using tbl_foo_id_1 on public.tbl_foo (cost=0.14..13.26 rows=42 width=8) (actual time=0.026..0.026 rows=1 loops=1) Output: id Filter: (tbl_foo.created_at >= '2017-01-15 00:00:00'::timestamp without time zone) Rows Removed by Filter: 13 Planning time: 0.162 ms Execution time: 0.087 ms (8 rows) explain analyze verbose select id from tbl_foo where created_at >= '2017-01-15' and id is not null order by id limit 1; QUERY PLAN Limit (cost=0.14..0.45 rows=1 width=8) (actual time=0.042..0.047 rows=1 loops=1) Output: id -> Index Scan using tbl_foo_id_null on public.tbl_foo (cost=0.14..13.28 rows=43 width=8) (actual time=0.029..0.029 rows=1 loops=1) Output: id Index Cond: (tbl_foo.id IS NOT NULL) Filter: (tbl_foo.created_at >= '2017-01-15 00:00:00'::timestamp without time zone) Rows Removed by Filter: 14 Planning time: 0.129 ms Execution time: 0.096 ms -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] odd optimizer result, index condition "is not null" on column defined as "not null"
Hi, following up my own post: I noted that I included the "set enable_seqscan=off; ". But the results I mentioned are from before this statement. I also compared some more statements explain analyze verbose select min(id) from tbl_foo where created_at >= '2017-01-15' ; explain analyze verbose select id from tbl_foo where created_at >= '2017-01-15' order by id limit 1; Those 2 are the same, but the 2nd skips the "not null" index condition. explain analyze verbose select min(id) filter(where created_at >= '2017-01-15') from tbl_foo; explain analyze verbose select min(id) filter(where created_at >= '2017-01-15') from tbl_foo where created_at >= '2017-01-15'; They should also be considered the same, as the "where" only removes rows, that are skipped by the "filter" anyway. It seems the filter changes the plan to the other index. But adding the where reduces the amount of "rows" that is scanned on this index. This is nothing todo with the original question of the "is not null" condition on the "not null" field. But it seems that, if "created_at" is only in the where part, the optimizer does not consider using "created_at" from the index (and doing an index only scan). If "created_at" is in the select part, then the optimizer considers the "index only scan". (and even uses it for the "where" part) To check this I tried explain analyze verbose select min(created_at), min(id) filter(where created_at >= '2017-01-15') from tbl_foo; and it gives an index only as well. Out of interest, anyone with 9.6.2, does it yield the same results? On 03/03/2017 16:41, Martin F wrote: CREATE TABLE if not exists tbl_foo( id bigserial NOT NULL primary key, created_at timestamp without time zone NOT NULL ); create index tbl_foo_date on tbl_foo using btree (created_at,id); insert into tbl_foo (created_at) values ('2017-01-01'), ('2017-01-02'), ('2017-01-03'), ('2017-01-04'), ('2017-01-05'), ('2017-01-06'), ('2017-01-07'), ('2017-01-08'), ('2017-01-09'), ('2017-01-10'), ('2017-01-11'), ('2017-01-12'), ('2017-01-13'), ('2017-01-14'), ('2017-01-15'), ('2017-01-16'), ('2017-01-17'), ('2017-01-18'), ('2017-01-19'), ('2017-01-20'), ('2017-01-21'), ('2017-01-22'), ('2017-01-23'), ('2017-01-24'), ('2017-01-25'), ('2017-01-26'), ('2017-01-27'), ('2017-01-28'), ('2017-01-29'), ('2017-02-02'), ('2017-02-02'), ('2017-02-03'), ('2017-02-04'), ('2017-02-05'), ('2017-02-06'), ('2017-02-07'), ('2017-02-08'), ('2017-02-09'), ('2017-02-10'), ('2017-02-11'), ('2017-02-12'), ('2017-02-13'), ('2017-02-14'), ('2017-02-15'), ('2017-02-16'), ('2017-02-17'), ('2017-02-18'), ('2017-02-19'), ('2017-02-20'), ('2017-02-21'), ('2017-02-22'), ('2017-02-23'), ('2017-02-24'), ('2017-02-25'), ('2017-02-26'), ('2017-02-27'), ('2017-02-28'); analyze tbl_foo; explain analyze verbose select min(id) from tbl_foo where created_at >= '2017-01-15'; explain analyze verbose select min(id) filter(where created_at >= '2017-01-15') from tbl_foo; set enable_seqscan=off; explain analyze verbose select min(id) from tbl_foo where created_at >= '2017-01-15'; explain analyze verbose select min(id) filter(where created_at >= '2017-01-15') from tbl_foo; drop TABLE tbl_foo; -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
[GENERAL] odd optimizer result, index condition "is not null" on column defined as "not null"
Hi. I am new, and not sure which mailinglist this should go to, so I start with the general list. (please advice, if I should send this to a more specific list) This is tested with postgresql 9.5.5 (Maybe someone can confirm, if it is the same with later versions, saving me the work to upgrade right now, thanks) See the sql below. The select without "filter" produces Result (cost=0.45..0.46 rows=1 width=0) (actual time=0.229..0.234 rows=1 loops=1) Output: $0 InitPlan 1 (returns $0) -> Limit (cost=0.14..0.45 rows=1 width=8) (actual time=0.161..0.166 rows=1 loops=1) Output: tbl_foo.id -> Index Scan using tbl_foo_pkey on public.tbl_foo (cost=0.14..13.28 rows=43 width=8) (actual time=0.045..0.045 rows=1 loops=1) Output: tbl_foo.id Index Cond: (tbl_foo.id IS NOT NULL) Filter: (tbl_foo.created_at >= '2017-01-15 00:00:00'::timestamp without time zone) Rows Removed by Filter: 14 Planning time: 1.792 ms Execution time: 0.273 ms Index Cond: (tbl_foo.id IS NOT NULL) only "id" is the pk, and declared "not null". So why this index condition? The select with filter choose an IMHO better plan Index Only Scan using tbl_foo_date on public.tbl_foo Should the first optimizer result be considered a bug? Should it be reported somewhere? CREATE TABLE if not exists tbl_foo( id bigserial NOT NULL primary key, created_at timestamp without time zone NOT NULL ); create index tbl_foo_date on tbl_foo using btree (created_at,id); insert into tbl_foo (created_at) values ('2017-01-01'), ('2017-01-02'), ('2017-01-03'), ('2017-01-04'), ('2017-01-05'), ('2017-01-06'), ('2017-01-07'), ('2017-01-08'), ('2017-01-09'), ('2017-01-10'), ('2017-01-11'), ('2017-01-12'), ('2017-01-13'), ('2017-01-14'), ('2017-01-15'), ('2017-01-16'), ('2017-01-17'), ('2017-01-18'), ('2017-01-19'), ('2017-01-20'), ('2017-01-21'), ('2017-01-22'), ('2017-01-23'), ('2017-01-24'), ('2017-01-25'), ('2017-01-26'), ('2017-01-27'), ('2017-01-28'), ('2017-01-29'), ('2017-02-02'), ('2017-02-02'), ('2017-02-03'), ('2017-02-04'), ('2017-02-05'), ('2017-02-06'), ('2017-02-07'), ('2017-02-08'), ('2017-02-09'), ('2017-02-10'), ('2017-02-11'), ('2017-02-12'), ('2017-02-13'), ('2017-02-14'), ('2017-02-15'), ('2017-02-16'), ('2017-02-17'), ('2017-02-18'), ('2017-02-19'), ('2017-02-20'), ('2017-02-21'), ('2017-02-22'), ('2017-02-23'), ('2017-02-24'), ('2017-02-25'), ('2017-02-26'), ('2017-02-27'), ('2017-02-28'); analyze tbl_foo; explain analyze verbose select min(id) from tbl_foo where created_at >= '2017-01-15'; explain analyze verbose select min(id) filter(where created_at >= '2017-01-15') from tbl_foo; set enable_seqscan=off; explain analyze verbose select min(id) from tbl_foo where created_at >= '2017-01-15'; explain analyze verbose select min(id) filter(where created_at >= '2017-01-15') from tbl_foo; drop TABLE tbl_foo; -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general