83 lines
3.0 KiB
Python
83 lines
3.0 KiB
Python
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import sqlalchemy as sa
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# Deliberately the same shape of query the test suite's own EXPLAIN check runs
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# against the schema directly (tests/test_pathologies.py, 6.4) -- kept here
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# only for the honest (non-n_plus_one) path; that test doesn't call this code.
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_N_PLUS_ONE_ROW_CAP = 1500
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async def account_exists(session, account_id: str) -> bool:
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result = await session.execute(sa.text("SELECT 1 FROM accounts WHERE id = :id"), {"id": account_id})
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return result.first() is not None
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async def compute_summary(session, account_id: str, *, n_plus_one: bool) -> dict:
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if n_plus_one:
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rows = await _n_plus_one_summary(session, account_id)
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else:
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rows = await _joined_summary(session, account_id)
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total_count = 0
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total_amount = 0
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by_category: dict = {}
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for r in rows:
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total_count += 1
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total_amount += r["amount_minor"]
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label = r["label"] or "uncategorized"
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entry = by_category.setdefault(label, {"count": 0, "total_amount_minor": 0})
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entry["count"] += 1
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entry["total_amount_minor"] += r["amount_minor"]
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return {
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"account_id": account_id,
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"window_days": 120,
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"transaction_count": total_count,
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"total_amount_minor": total_amount,
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"by_category": by_category,
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}
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async def _joined_summary(session, account_id: str) -> list[dict]:
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"""The honest path: a single JOIN, one statement."""
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result = await session.execute(
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sa.text(
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"SELECT t.amount_minor, mc.label FROM transactions t "
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"LEFT JOIN merchant_categories mc ON mc.id = t.category_id "
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"WHERE t.account_id = :aid AND t.created_at >= now() - interval '120 days'"
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),
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{"aid": account_id},
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)
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return [dict(row) for row in result.mappings().all()]
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async def _n_plus_one_summary(session, account_id: str) -> list[dict]:
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"""n_plus_one: instead of the JOIN above, fetch rows without one and issue
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a separate category lookup per row -- phase-0-base-project-spec.md §7.
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Capped so the pathology stays a genuine multiplication of statements
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(see tests/test_pathologies.py 6.3) without turning a single request into
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an unbounded number of round trips on a high-volume hot account."""
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result = await session.execute(
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sa.text(
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"SELECT amount_minor, category_id FROM transactions "
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"WHERE account_id = :aid AND created_at >= now() - interval '120 days' "
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f"LIMIT {_N_PLUS_ONE_ROW_CAP}"
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),
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{"aid": account_id},
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)
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tx_rows = result.mappings().all()
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rows = []
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for tx_row in tx_rows:
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label = None
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if tx_row["category_id"] is not None:
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cat_result = await session.execute(
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sa.text("SELECT label FROM merchant_categories WHERE id = :id"),
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{"id": tx_row["category_id"]},
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)
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cat_row = cat_result.first()
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if cat_row is not None:
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label = cat_row.label
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rows.append({"amount_minor": tx_row["amount_minor"], "label": label})
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return rows
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