29b45dd234
- Adds `skills/postgres-best-practices/`: A new skill containing comprehensive Postgres performance optimization rules and guidelines from Supabase. - The skill includes rules for query performance, connection management, security (RLS), and schema design. - Updates `README.md` to include the new skill in the directory.
50 lines
1.4 KiB
Markdown
50 lines
1.4 KiB
Markdown
---
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title: Index JSONB Columns for Efficient Querying
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impact: MEDIUM
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impactDescription: 10-100x faster JSONB queries with proper indexing
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tags: jsonb, gin, indexes, json
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---
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## Index JSONB Columns for Efficient Querying
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JSONB queries without indexes scan the entire table. Use GIN indexes for containment queries.
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**Incorrect (no index on JSONB):**
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```sql
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create table products (
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id bigint primary key,
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attributes jsonb
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);
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-- Full table scan for every query
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select * from products where attributes @> '{"color": "red"}';
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select * from products where attributes->>'brand' = 'Nike';
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```
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**Correct (GIN index for JSONB):**
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```sql
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-- GIN index for containment operators (@>, ?, ?&, ?|)
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create index products_attrs_gin on products using gin (attributes);
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-- Now containment queries use the index
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select * from products where attributes @> '{"color": "red"}';
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-- For specific key lookups, use expression index
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create index products_brand_idx on products ((attributes->>'brand'));
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select * from products where attributes->>'brand' = 'Nike';
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```
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Choose the right operator class:
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```sql
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-- jsonb_ops (default): supports all operators, larger index
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create index idx1 on products using gin (attributes);
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-- jsonb_path_ops: only @> operator, but 2-3x smaller index
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create index idx2 on products using gin (attributes jsonb_path_ops);
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```
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Reference: [JSONB Indexes](https://www.postgresql.org/docs/current/datatype-json.html#JSON-INDEXING)
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