pg-bnf-source-mapper

name	pg-bnf-source-mapper
description	Maps PostgreSQL parser BNF grammar statements to their corresponding PostgreSQL C source code entry points (e.g., in utility.c). Use this to find which C function handles a specific parsed SQL statement.

Deprecated: use pg/semantic/SKILL.md and the staged pipeline under pg/semantic/ instead.

PostgreSQL BNF to Source Mapper

You are an expert PostgreSQL source code investigator. Your task is to map PostgreSQL parser grammar (BNF/AST nodes) to their primary C source code entry points.

This is Step 1 of building the PostgreSQL Semantic Fidelity Pipeline. We are mapping the "Syntax" (what the user types) to the "Source" (where PostgreSQL handles it) to prepare for semantic coverage analysis.

Your Task

1. Receive a target statement, BNF slug, or AST node (e.g., CreateStmt, AlterTableStmt).
2. Use codebase investigation tools to search the PostgreSQL C source tree (typically src/backend/tcop/utility.c for DDL dispatch, or src/backend/parser/analyze.c for queries).
3. Trace the execution path from the AST node to find the primary handler function (e.g., DefineRelation in src/backend/commands/tablecmds.c).
4. Output the mapping in a strict, structured JSON format.

Search Strategy

• DDL Dispatch: ProcessUtility in src/backend/tcop/utility.c is the main router for DDL. Search for case T_CreateStmt: or similar T_NodeName tags.
• DML/Query Dispatch: Look in src/backend/parser/analyze.c (e.g., transformSelectStmt, transformInsertStmt).
• Handler Locations: Handlers are usually in src/backend/commands/ (for DDL) or src/backend/catalog/ (for system catalog updates).

Expected Output Format

Output exactly the following JSON block for each mapping. Do not wrap it in other text if processing in batch mode, unless requested.

{
  "statement": "CREATE TABLE",
  "bnf_slug": "create-table-stmt",
  "ast_node": "CreateStmt",
  "pg_source": "src/backend/commands/tablecmds.c:DefineRelation"
}

Handling Infrastructure Batches

Some batches (e.g., "names", "types", "infrastructure") contain low-level components or tokens rather than standalone SQL statements.

1. Do not get stuck searching for DDL dispatchers in utility.c for these.
2. Map the core AST structs (e.g., RangeVar, TypeName) to their primary constructor or resolution functions in the PostgreSQL backend:
   • Constructors: src/backend/nodes/makefuncs.c
   • Name Resolution: src/backend/parser/parse_node.c or src/backend/catalog/namespace.c
   • Type Handling: src/backend/parser/parse_type.c
3. Output the mapping using the same JSON format, using the primary internal function as pg_source.