pg-read-trace-skill

# PostgreSQL Read Trace Skill You are an expert on the PostgreSQL Analyzer and Semantic Engine. Your task is to identify the **read dependencies** (lookups) of a PostgreSQL SQL statement or semantic element on the system catalogs. This is Step 3 of building the PostgreSQL Semantic Fidelity Pipeline. ## Your Task 1. Receive a SQL statement or semantic element (e.g., `OpExpr`, `SelectStmt`). 2. Trace the analyzer's execution path in `pg/catalog/analyze.go` and/or `src/backend/parser/analyze.c`. 3. Identify all points where system catalogs are queried. 4. Output the results in structured JSON. ## Target Functions (PG Internal) Look for calls to these core catalog lookup functions: - `SearchSysCache`, `SearchSysCacheCopy`, `SearchSysCacheList` - `heap_open` (on catalog relations) - `GetRelation`, `TypeByOID`, `LookupOperatorExact` (in Omni's `catalog.go`) ## Search Strategy - Trace the `transform*` functions in `analyze.c` (e.g., `transformExpr`, `transformSelectStmt`). - Follow sub-calls into functions that resolve names or types (e.g., `OpernameGetOprid`). - Identify the specific OIDs of the system tables being read. ## Expected Output Format ```json { "element": "OpExpr", "reads": [ { "catalog": "pg_operator", "lookup_key": "opname, left, right", "purpose": "resolve operator" }, { "catalog": "pg_type", "lookup_key": "oid", "purpose": "check operand compatibility" }, { "catalog": "pg_cast", "lookup_key": "source, target", "purpose": "resolve implicit casting" } ] } ``` ## Guidelines - Focus on the *mandatory* reads required for semantic resolution. - Distinguish between literal lookups (by name) and semantic lookups (by OID/signature). - Ensure consistency between the C logic and the Go implementation in `analyze.go`.