#3565 perf(mappers): Optimize stream map expression evaluation Pull request opened by edgarrmondragon Summary After the simpleeval compatibility fix was merged in #3595, this PR contains stream map performance optimizations — a 34% improvement on

test_bench_simple_map_transforms

(547 ms → 407 ms). Optimizations 1. Pre-build static

names

dict at init time Entries that never change across records —

config

,

__stream_name__

,

__original_stream_name__

, and

fake

— are assembled once in

__init__

into

_static_eval_names

. Previously these were re-inserted into a fresh dict inside

_eval

on every single property of every single record. 2. Build the

names

dict once per record, not once per field The

transform_fn

closure now calls

_build_eval_names(record)

once and passes the result to every

_eval

call for that record.

_eval

only patches the

self

key (the current property's original value) before each evaluation. Previously a full

record.copy()

plus several dict assignments happened inside

_eval

for every transformed property. 3. Pre-evaluate constant expressions at init time

_is_constant_expression

inspects the parsed AST of each mapping expression. If all

Name

nodes refer to known function names (and therefore not to record variables), the expression is evaluated once during

_init_functions_and_schema

and its result is cached. For every subsequent record the cached value is used directly, bypassing simpleeval entirely. Related • Closes #3561 • danthedeckie/simpleeval#176 • #3595 (simpleeval 1.0.5 compatibility, already merged to

main

) • #3605 / #3606 (debug-log removal, merged separately — no measured performance impact per CodSpeed) Summary by Sourcery Optimize stream map expression evaluation in the mapper for improved performance while preserving existing behavior. Enhancements: • Precompute a static evaluation context for config and stream metadata and reuse it across record evaluations. • Build the expression evaluator names dictionary once per record and reuse it for all property transformations within that record. • Introduce detection and pre-evaluation of constant mapping expressions so their results can be reused without re-invoking the expression evaluator. • Extend the mapper function type aliasing to support simpleeval module wrappers alongside callables. meltano/sdk