Execution plan
An execution plan is a structured description of the operations or tasks arranged to carry out a query or other task.
Just Use Postgres!
A query execution plan is the database engine's planned sequence of operations for executing a SQL query, optionally including runtime analysis.
- How it is used
- Diagnoses query behavior and guides optimization decisions before adding or changing indexes.
- How deep it goes
- Explains plan nodes, runtime metrics, scans, joins, aggregation, sorting, and planner tradeoffs without covering complete optimizer internals.
- Examples
- Demonstrates CTE ranking, player statistics, regional filtering, JSON expression indexes, and time-series aggregation plans.
- What you can do after
- Diagnose query costs with PostgreSQL EXPLAIN and EXPLAIN ANALYZE, then evaluate whether indexes or query changes improve execution.
100 SQL Server Mistakes and How to Avoid Them
A query plan is the execution strategy selected or generated for processing a database query.
- How it is used
- Diagnoses query performance by revealing the operators and strategy selected to return requested data.
- How deep it goes
- Explains optimizer-selected operators, estimated cost, plan access, and hints, but stops short of exhaustive optimizer internals.
- Examples
- Compares CustomerContacts scans with and without ORDER BY, then contrasts Nested Loops and forced Hash Join plans for a join.
- What you can do after
- Diagnose query performance with actual plans, compare operator costs, and prefer indexes or investigation before applying hints.
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MongoDB 8.0 in Action, Third Edition
A query execution plan is the database engine's strategy and sequence of operations for processing a query and returning its results.
- How it is used
- Diagnoses query efficiency by revealing selected operations, index use, examined data, and execution time.
- How deep it goes
- Explains plan selection, caching, execution stages, and runtime statistics, but does not detail planner internals beyond available output.
- Examples
- Uses mongosh explain commands and an IXSCAN-to-FETCH plan with execution statistics.
- What you can do after
- Diagnose query efficiency with db.collection.explain(), cursor.explain(), and selected verbosity modes.
Read how MongoDB 8.0 in Action, Third Edition explains execution plan →
PostgreSQL Mistakes and How to Avoid Them
A query plan is a representation of the operations and access methods a database system will use to execute a query.
- How it is used
- Diagnose slow PostgreSQL queries by exposing selected scan methods, filters, and index access paths.
- How deep it goes
- Explains planner cost selection, statistics and configuration inputs, scan choices, and EXPLAIN ANALYZE actual timings.
- Examples
- Uses an open-ticket count that moves from a sequential scan to an Index Only Scan through indexing.
- What you can do after
- Diagnose/debug with EXPLAIN and EXPLAIN ANALYZE to identify slow query paths and evaluate indexing tradeoffs.
Read how PostgreSQL Mistakes and How to Avoid Them explains execution plan →
Related concepts
- EXPLAINproduced by · EXPLAIN is an SQL statement that reports a query’s execution plan and, when analyzing execution, may include observed runtime statistics.
- query plannerproduced by · A query planner is a database component that evaluates possible execution strategies and constructs or selects a plan for a query.
- optimizationproduced by · Optimization is the systematic selection or adjustment of values, actions, or system designs to improve a specified objective, often subject to constraints.
- SQLproduced by · SQL is a standardized declarative language for defining, querying, and manipulating data in relational database systems.
- query hintconfigured by · A query hint is a directive that influences database query execution, optimization, or result handling.
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