Partial index
A partial index is a database index containing entries only for records that satisfy a specified predicate.
Just Use Postgres!
A partial index is a database index that contains entries only for table rows satisfying a specified condition.
- How it is used
- Optimizes queries that repeatedly target a small, condition-defined subset of table rows.
- How deep it goes
- Explains predicates, storage and update benefits, and EXPLAIN behavior through SQL examples without covering index internals.
- Examples
- Demonstrates occasional-player tracking, active message queues, and named geospatial points with non-null names.
- What you can do after
- Operate/configure PostgreSQL partial indexes and diagnose their use with EXPLAIN execution plans.
MongoDB 8.0 in Action, Third Edition
A partial index indexes only documents that satisfy a specified filter expression.
- How it is used
- Improves indexing efficiency when only documents meeting a defined condition need indexed access.
- How deep it goes
- Defines filtered indexing, explains supported operators and cost benefits, and demonstrates one compound example without deeper planner analysis.
- Examples
- Uses a movies collection index on year, type, and imdb.rating filtered to documents where type equals "movie".
- What you can do after
- Apply it via db.collection.createIndex() with indexed fields and a partialFilterExpression.
Read how MongoDB 8.0 in Action, Third Edition explains partial index →
Related concepts
- indexingkind of · Indexing is the organization or use of positions, keys, or lookup structures to identify and retrieve selected data or elements.
- createIndex()configured by · createIndex() is a MongoDB database method that creates an index on a collection with specified key and option definitions.
- where clauseconfigured by · A WHERE clause is a query-language clause that restricts returned or affected records to those satisfying a specified predicate.
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