113. The Action's Rule Name Is Set, Not Restored

• Status: Implemented
• Date: 2026-10-22

#Problem and Mechanism

A direct rule with an action saved p.Where (the rule whose action is being evaluated), set it to the rule's name, ran the action and wrote the saved value back: three statements and a saved variable for every action: 422 actions (844 removed statements) in the duckdb parser.

p.Where is read in one place, the parse-level handler that turns an evalError into the error text action in <rule>: .... Actions never nest, predicates and bindings recover their own evalError, and the errors of the result conversion are fatal errors with their own text, so an evalError reaches the handler only from inside an action, after that action set the name. Restoring the previous value therefore changes nothing observable. The generated action now sets p.Where and leaves it.

TestGeneratedDirectActionErrorContextAndParserReuse compares the error text with the engine, including a failing action that runs after another rule's action succeeded.

#Results

parser.go with -typed-only, bytes and lines before and after:

The duckdb test binary shrinks from 17,078,738 to 17,029,202 bytes (-0.3%). Parse speed (30 interleaved rounds, minimum, an identical copy as the control) is within noise: python +0.40% (control -0.11%), cue -0.26% (+0.10%), duckdb -0.93% (-0.38%), cel -0.85% (-0.08%).

#Decision and Limits

Adopted. A future action-like evaluation that nests parsing inside an action, or an evalError raised outside an action and outside a predicate, must set or restore the name itself.