Module plan 

Query plan caching for prepared statements

This module provides cached execution plans that bypass the full query planning pipeline for simple query patterns. When a prepared statement is created, we analyze the AST to detect patterns that can use fast execution paths.

Supported Patterns

Primary Key Point Lookup

Queries like SELECT * FROM table WHERE pk_col = ? are detected and cached with:

• Table name
• Primary key column indices in schema
• Parameter indices for PK values
• Projection column indices (or wildcard flag)

At execution time, this allows direct index lookup without:

• Re-parsing the AST
• Checking if it’s a simple query
• Resolving table/column names
• Building schema objects

Performance Impact

For simple point SELECT via prepared statement:

• Without plan caching: ~60µs (AST manipulation, pattern detection, table lookup)
• With plan caching: ~1-5µs (direct index lookup)

Cache Invalidation

Cached plans are invalidated when:

• DDL modifies the referenced table (schema change)
• The table is dropped
• Indexes are added/removed

Structs

ColumnProjection

A single column in the projection

PkDeletePlan

Cached plan for primary key DELETE statements DELETE FROM table WHERE pk_col = ? [AND pk_col2 = ? …]

PkPointLookupPlan

Cached plan for primary key point lookup queries

ResolvedProjection

Resolved projection information cached after first execution

SimpleFastPathPlan

Cached plan for simple fast-path eligible queries

Enums

CachedPlan

Cached execution plan for a prepared statement

ProjectionPlan

How to project columns from the result

Functions

analyze_for_plan

Analyze a prepared statement and create a cached plan if possible