planner used functional index in 7.3.6, now does a seq scan in 7.4.7 after upgrade
От | Chris Tennant |
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Тема | planner used functional index in 7.3.6, now does a seq scan in 7.4.7 after upgrade |
Дата | |
Msg-id | 455FF56D.7030001@elirious.com обсуждение исходный текст |
Ответы |
Re: planner used functional index in 7.3.6, now does a seq scan in 7.4.7 after upgrade
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Список | pgsql-sql |
Greetings, I've just upgraded from 7.3.6 to 7.4.7 (running on Debian Linux). I dumped and reloaded my db as part of the upgrade. Everything is working great, except that one query that executed in < 1 ms on 7.3.6 now takes > 500 ms on 7.4.7. When I look at the query plan,the planner is no longer taking advantage of a functional index (the index is correctly defined as immutable), and is doing a sequence scan instead. I'm stumped -- I can't see any reason why this would be broken. Out of desperation, I tried dropping and recreating the index, and dropping and recreating the function. I've also run "ANALYZE" on the tables, in addition to the regular analysis and vacuums that I run frequently as part of regular maintenance. No luck. Has anyone else run into something like this? Any hints would be much appreciated. FWIW, I've provided all the gory details below. Thank you!! Chris ---------------- This is the query: SELECT data_stored.id as data_stored_id, patient_data.id as patient_data_id, stereo_image_attributes.id as stereo_id, stereo_image_attributes.x_offsetas stereo_x_offset, stereo_image_attributes.y_offsetas stereo_y_offset, stereo_image_attributes.stereo_swapas stereo_swap, stereo_image_attributes.analysis_dateas stereo_analysis_date, stereo_image_attributes.analysis_detailas stereo_analysis_detail, stereo_image_attributes.analysis_storage_idas stereo_analysis_storage_id FROM opt_stereo_pair_image_attributes stereo_image_attributes, opt_patient_data patient_data, opt_patient_data_entries patient_data_entry, opt_patient_data_stored data_stored WHERE patient_data.version_id = ? AND patient_data_entry.patient_data_id = patient_data.idAND patient_data_entry.id = data_stored.patient_data_entry_id AND data_stored.id = stereo_id ( stereo_image_attributes.left_patient_data_stored_id, stereo_image_attributes.right_patient_data_id stereo_image_attributes.left_patient_data_id ) I then run EXPLAIN ANALYZE on 7.3.6 and 7.4.7, with the same query parameter. here's what EXPLAIN ANALYZE yields on 7.3.6. note that it *is* using the functional index "stereo_pair_image_attributes_stereo_id" QUERY PLAN -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Nested Loop (cost=0.00..5331.34 rows=2 width=64) (actual time=0.13..0.52 rows=2 loops=1) -> Nested Loop (cost=0.00..153.23 rows=4 width=20) (actual time=0.10..0.45 rows=7 loops=1) -> Nested Loop (cost=0.00..8.52 rows=16 width=12) (actual time=0.05..0.18 rows=37 loops=1) -> Index Scan using patient_data_version_id on opt_patient_data patient_data (cost=0.00..4.75 rows=1 width=4) (actual time=0.03..0.03 rows=1 loops=1) Index Cond: (version_id = 323268) -> Index Scan using opt_patient_data_id_keyon opt_patient_data_entries patient_data_entry (cost=0.00..3.40 rows=30 width=8) (actual time=0.01..0.09 rows=37 loops=1) Index Cond: (patient_data_entry.patient_data_id = "outer".id) -> Index Scan using opt_patient_data_stored_entry_count on opt_patient_data_stored data_stored (cost=0.00..8.85 rows=2 width=8) (actual time=0.01..0.01 rows=0 loops=37) Index Cond: ("outer".id = data_stored.patient_data_entry_id) -> IndexScan using stereo_pair_image_attributes_stereo_id on opt_stereo_pair_image_attributes stereo_image_attributes (cost=0.00..1454.62 rows=451 width=44) (actual time=0.01..0.01 rows=0 loops=7) Index Cond: ("outer".id = stereo_id(stereo_image_attributes.left_patient_data_stored_id, stereo_image_attributes.right_patient_data_id, stereo_image_attributes.left_patient_data_id))Total runtime: 0.62 msec (12 rows) And then on 7.4.7. note that it is *not* using the functional index, but is instead doing a seq scan on opt_stereo_pair_image_attributes. QUERY PLAN -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Hash Join (cost=173.16..2628.80 rows=2 width=40) (actual time=245.433..581.288 rows=2 loops=1) Hash Cond: (stereo_id("outer".left_patient_data_stored_id, "outer".right_patient_data_id, "outer".left_patient_data_id) = "inner".id) -> Seq Scan on opt_stereo_pair_image_attributes stereo_image_attributes (cost=0.00..1793.21 rows=88321 width=44) (actual time=0.004..162.218 rows=88321 loops=1) -> Hash (cost=173.15..173.15 rows=4 width=8) (actual time=0.709..0.709 rows=0 loops=1) -> Nested Loop (cost=0.00..173.15 rows=4 width=8) (actual time=0.114..0.691 rows=7 loops=1) -> Nested Loop (cost=0.00..8.44 rows=17 width=8) (actual time=0.042..0.280 rows=37 loops=1) -> Index Scan using patient_data_version_id on opt_patient_data patient_data (cost=0.00..4.76 rows=1 width=4) (actual time=0.019..0.021 rows=1 loops=1) Index Cond: (version_id = 323268) -> IndexScan using opt_patient_data_id_key on opt_patient_data_entries patient_data_entry (cost=0.00..3.35 rows=26 width=8) (actual time=0.013..0.110 rows=37 loops=1) Index Cond: (patient_data_entry.patient_data_id = "outer".id) -> Index Scan using opt_patient_data_stored_entry_count on opt_patient_data_stored data_stored (cost=0.00..9.66 rows=2 width=8) (actual time=0.006..0.007 rows=0 loops=37) Index Cond: ("outer".id = data_stored.patient_data_entry_id)Total runtime: 581.390 ms (13 rows) Here are the schema details for the table with the functional index: Table "public.opt_stereo_pair_image_attributes" Column | Type | Modifiers ------------------------------+-----------------------------+--------------------id | integer | not nullleft_patient_data_stored_id | integer | not nullright_patient_data_stored_id| integer | not nullx_offset | integer | default 0y_offset | integer | default 0analysis_date |timestamp without time zone |analysis_detail | integer |analysis_storage_id |integer |stereo_swap | integer | default 0left_patient_data_id | integer | not nullright_patient_data_id | integer | not nullanalysis_type_id | integer | not null default 0 Indexes: "opt_stereo_pair_image_attributes_pkey" primary key, btree (id) "opt_stereo_pair_image_attributes_stereo_key"unique, btree (left_patient_data_stored_id, right_patient_data_stored_id) "stereo_pair_image_attributes_stereo_id" btree (stereo_id(right_patient_data_id, left_patient_data_id)) Foreign-key constraints: "analysis_type_id" FOREIGN KEY (analysis_type_id) REFERENCES opt_analysis_types(id) "left_patient_data_id" FOREIGN KEY (left_patient_data_id) REFERENCES opt_patient_data(id) "right_patient_data_id" FOREIGN KEY (right_patient_data_id) REFERENCES opt_patient_data(id) "opt_stereo_pair_image_attributes_right_patient_data_stored" FOREIGN KEY (right_patient_data_stored_id) REFERENCES opt_patient_data_stored(id) "opt_stereo_pair_image_attributes_left_patient_data_stored"FOREIGN KEY (left_patient_data_stored_id) REFERENCES opt_patient_data_stored(id) here's the definition of the function (as immutable): CREATE OR REPLACE FUNCTION stereo_id (INTEGER, INTEGER, INTEGER) RETURNS INTEGER AS 'BEGIN RETURN CASE WHEN $2 = $3 THEN $1 ELSE -1 END; END;' LANGUAGE 'plpgsql' IMMUTABLE; and here's the original definition of the functional index: CREATE INDEX stereo_pair_image_attributes_stereo_id ON opt_stereo_pair_image_attributes (stereo_id(right_patient_data_id,left_patient_data_id));