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Sarj Standards

Python · architecture

no-query-with-many-joins

python:no-query-with-many-joins

Store queries should use at most two explicit or implicit joins.

Code
SARJ019
Default
error
Fix
none
Languages
python

Why

Wide join graphs couple store reads to many tables and make query cost and schema changes harder to control.

Fix

Split the read into focused store operations or denormalize data needed together.

Before / after

Executed by this rule’s unit tests.

Before

Query with three joins

app/task_store.py · focus
QUERY = "SELECT a.id FROM a JOIN b ON TRUE JOIN c ON TRUE JOIN d ON TRUE"

After

Query with two joins

app/task_store.py · focus
QUERY = "SELECT a.id FROM a JOIN b ON TRUE JOIN c ON TRUE"

Limits

  • Only SQL string literals in recognized store modules are analyzed.
  • The rule counts join syntax; it does not estimate a database query plan.