PostgreSQL as a secret weapon for high-performance ... - PGCon

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Postgres Experience > Limit/Offset Be careful with subselects: they are executed limit + offset times! Use joins to overcome the limitation Gleb Arshinov & Alex Dymo ● PostgreSQL as a secret weapon for high-performance Ruby on Rails applications ● PGCon 2010 44 / 58
Postgres Experience > in() and Joins Use any(array ()) instead of in() to force subselect and avoid join explain analyze select * from issues where id in (select issue_id from tags_issues); QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------------------------------- Merge IN Join (actual time=0.096..576.704 rows=55363 loops=1) Merge Cond: (issues.id = tags_issues.issue_id) -> Index Scan using issues_pkey on issues (actual time=0.027..270.557 rows=229991 loops=1) -> Index Scan using tags_issues_issue_id_key on tags_issues (actual time=0.051..73.903 rows=70052loops=1) Total runtime: 605.274 ms explain analyze select * from issues where id = any( array( (select issue_id from tags_issues) ) ); QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------ Bitmap Heap Scan on issues (actual time=247.358..297.932 rows=55363 loops=1) Recheck Cond: (id = ANY ($0)) InitPlan -> Seq Scan on tags_issues (actual time=0.017..51.291 rows=70052 loops=1) -> Bitmap Index Scan on issues_pkey (actual time=246.589..246.589 rows=70052 loops=1) Index Cond: (id = ANY ($0)) Total runtime: 325.205 ms 2x! Gleb Arshinov & Alex Dymo ● PostgreSQL as a secret weapon for high-performance Ruby on Rails applications ● PGCon 2010 45 / 58
Page 1 and 2: Gleb Arshinov, Alexander Dymo PGCon
Page 3 and 4: Web Development Pains ● Performan
Page 5 and 6: Outline ● Rails as ORM ● Optimi
Page 7 and 8: Rails as ORM > Myths and Realities
Page 9 and 10: Rails as ORM > Multiplying Queries
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Page 13 and 14: Rails as ORM > Query Tests rev 834:
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Page 21 and 22: Rails Performance > Ruby ● Good l
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Page 27 and 28: Rails Performance > Solution Scalab
Page 29 and 30: Rails Performance > Solution Delega
Page 31 and 32: Rails Performance > Attribute Prelo
Page 33 and 34: Rails Performance > Access Control
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Page 37 and 38: Rails Performance > Aggregations Pe
Page 39 and 40: Postgres Experience > Good Things G
Page 41 and 42: Postgres Experience > Limitations A
Page 43: Postgres Experience > Limit/Offset
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Page 49 and 50: Postgres Approaches ● Benchmarkin
Page 51 and 52: Optimize Database > Basics How to o
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Page 57 and 58: Optimize Database > Postgres Config

PostgreSQL as a secret weapon for high-performance ... - PGCon

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