Weird, when I deleted an erroneous index it started picking a reasonable plan. This now works as expected, for posterity here is the bad plan:Nested Loop (cost=21281.50..21323812.82 rows=5621000 width=47) (actual time=171.648..7233.298 rows=85615 loops=1)
-> Function Scan on generate_series dates (cost=0.00..3.00 rows=1000 width=8) (actual time=0.031..0.252 rows=267 loops=1)
-> Unique (cost=21281.50..21290.08 rows=5621 width=39) (actual time=25.730..27.050 rows=321 loops=267)
-> Sort (cost=21281.50..21284.36 rows=5724 width=39) (actual time=25.728..26.242 rows=6713 loops=267)
Sort Key: alloc.note_id, alloc.series_id
Sort Method: quicksort Memory: 2220kB
-> Nested Loop (cost=10775.92..21210.05 rows=5724 width=39) (actual time=1.663..21.938 rows=6713 loops=267)
-> Hash Join (cost=10775.83..20355.61 rows=5724 width=52) (actual time=1.657..5.980 rows=6713 loops=267)
Hash Cond: (alloc.note_id = contrib.id)
-> Bitmap Heap Scan on portfolio_allocations alloc (cost=69.82..9628.13 rows=5724 width=39) (actual time=1.010..2.278 rows=6713 loops=267)
Recheck Cond: ((entity_id = '\x5787f132f50f7b03002cf835'::bytea) AND (allocated_on <= date(dates.dates)))
Heap Blocks: exact=118074
-> Bitmap Index Scan on portfolio_allocations_entity_id_allocated_on_idx (cost=0.00..69.53 rows=5724 width=0) (actual time=0.956..0.956 rows=6713 lo
Index Cond: ((entity_id = '\x5787f132f50f7b03002cf835'::bytea) AND (allocated_on <= date(dates.dates)))
-> Hash (cost=9464.85..9464.85 rows=354617 width=26) (actual time=169.792..169.792 rows=354617 loops=1)
Buckets: 524288 Batches: 1 Memory Usage: 24296kB
-> Seq Scan on contributions contrib (cost=0.00..9464.85 rows=354617 width=26) (actual time=0.007..83.246 rows=354617 loops=1)
-> Index Only Scan using investments_pkey on investments inv (cost=0.08..0.15 rows=1 width=13) (actual time=0.002..0.002 rows=1 loops=1792457)
Index Cond: (id = contrib.investment_id)
Heap Fetches: 1792457
Planning time: 0.721 ms
Execution time: 7236.507 ms
On Tue, Dec 5, 2017 at 10:04 AM Alex Reece <awreece@xxxxxxxxx> wrote:I get very different plan chosen when my query is in a lateral subquery vs standalone -- it doesn't use a key when joining on a table, instead opting to do a hash join. Here is the query:select distinct on (sub.entity_id, sub.note_id, sub.series_id)entity_id, note_id, series_idfrom(select alloc.entity_id, alloc.note_id, alloc.series_id, alloc.amount, inv.namefrom public.portfolio_allocations allocJOIN contributions contrib on contrib.id = alloc.note_idJOIN investments inv on inv.id = contrib.investment_idwhere entity_id = '\x5787f132f50f7b03002cf835' andalloc.allocated_on <= dates.date) subAnd wrapped inside the lateral:explain analyzeselect *from generate_series('2017-03-14 20:59:59.999'::TIMESTAMPTZ, current_timestamp::TIMESTAMP + INTERVAL '1 day', '24 hours') dates,LATERAL (... <SUB QUERY HERE> ...) latRun by itself injecting a hard coded value for dates.date, I get the expected plan which uses a key index on contributions:Unique (cost=14.54..14.54 rows=2 width=39) (actual time=0.052..0.053 rows=2 loops=1)-> Sort (cost=14.54..14.54 rows=2 width=39) (actual time=0.052..0.052 rows=2 loops=1)Sort Key: alloc.note_id, alloc.series_idSort Method: quicksort Memory: 25kB-> Nested Loop (cost=0.25..14.53 rows=2 width=39) (actual time=0.030..0.042 rows=2 loops=1)-> Nested Loop (cost=0.17..14.23 rows=2 width=52) (actual time=0.022..0.028 rows=2 loops=1)-> Index Scan using portfolio_allocations_entity_id_allocated_on_idx on portfolio_allocations alloc (cost=0.09..6.05 rows=2 width=39) (actual time=0.012..0.014Index Cond: ((entity_id = '\x5787f132f50f7b03002cf835'::bytea) AND (allocated_on <= '2017-03-14 20:59:59.999+00'::timestamp with time zone))-> Index Scan using contributions_id_accrue_from_idx on contributions contrib (cost=0.08..4.09 rows=1 width=26) (actual time=0.005..0.005 rows=1 loops=2)Index Cond: (id = alloc.note_id)-> Index Only Scan using investments_pkey on investments inv ( cost=0.08..0.15 rows=1 width=13) (actual time=0.005..0.006 rows=1 loops=2)Index Cond: (id = contrib.investment_id)Heap Fetches: 2Planning time: 0.617 msExecution time: 0.100 ms(15 rows)But run in the lateral, it doesn't use the index:Nested Loop (cost=14.54..24.55 rows=2000 width=47) (actual time=0.085..0.219 rows=534 loops=1)-> Function Scan on generate_series dates (cost=0.00..3.00 rows=1000 width=8) (actual time=0.031..0.043 rows=267 loops=1)-> Materialize (cost=14.54..14.55 rows=2 width=39) (actual time=0.000..0.000 rows=2 loops=267)-> Unique (cost=14.54..14.54 rows=2 width=39) (actual time=0.052..0.053 rows=2 loops=1)-> Sort (cost=14.54..14.54 rows=2 width=39) (actual time=0.051..0.052 rows=2 loops=1)Sort Key: alloc.note_id, alloc.series_idSort Method: quicksort Memory: 25kB-> Nested Loop (cost=0.25..14.53 rows=2 width=39) (actual time=0.029..0.041 rows=2 loops=1)-> Nested Loop (cost=0.17..14.23 rows=2 width=52) (actual time=0.021..0.027 rows=2 loops=1)-> Index Scan using portfolio_allocations_entity_id_allocated_on_idx on portfolio_allocations alloc (cost=0.09..6.05 rows=2 width=39) (actual time=0Index Cond: ((entity_id = '\x5787f132f50f7b03002cf835'::bytea) AND (allocated_on <= '2017-03-14 20:59:59.999+00'::timestamp with time zone))-> Index Scan using contributions_id_accrue_from_idx on contributions contrib (cost=0.08..4.09 rows=1 width=26) ( actual time=0.005..0.005 rows=1 looIndex Cond: (id = alloc.note_id)-> Index Only Scan using investments_pkey on investments inv ( cost=0.08..0.15 rows=1 width=13) (actual time=0.005..0.006 rows=1 loops=2)Index Cond: (id = contrib.investment_id)Heap Fetches: 2Planning time: 0.718 msExecution time: 0.296 ms(18 rows)For reference, here are the indexes on the relevant tables:Indexes:"portfolio_allocations_entity_id_allocated_on_idx" btree (entity_id, allocated_on DESC)"portfolio_allocations_note_id_allocated_on_idx" btree (note_id, allocated_on DESC)"portfolio_allocations_pnsa" btree (entity_id, note_id, series_id, allocated_on DESC)Indexes:"contributions_pkey" PRIMARY KEY, btree (id)"contributions_id_accrue_from_idx" btree (id, events_earnings_accrue_from)I have a few questions here:- Why doesn't it use the primary key index in either case?- Why isn't it choosing portfolio_allocations_pnsa, which seems like it would prevent it from having to sort?Best,~Alex
Argh, so sorry for repeated posts; I'll be very careful to review them before posting. The "good plan" was the result of me hard coding '2017-03-14 20:59:59.999+00'::timestamp of using dates.date inside the lateral subquery. When I correctly use dates.date, it takes 7000ms instead of 0.3ms. My questions still remain:
I have a few questions here:
- Why doesn't it use the primary key on contributions in either case, preferring contributions_id_accrue_from_idx or none at all?
- Why isn't it choosing portfolio_allocations_pnsa, which seems like it would prevent it from having to sort?
- What information can I gather to answer these questions on my own?
~Alex
On Tue, Dec 5, 2017 at 10:08 AM Alex Reece <awreece@xxxxxxxxx> wrote:
