fix(driver-memory): count a boolean aggregand as 1/0 in avg and sum

.changeset/memory-boolean-aggregand.md

@@ -0,0 +1,31 @@
+---
+"@objectstack/driver-memory": patch
+---
+
+**Bug fix (one query, two answers):** `avg` and `sum` over a **boolean** column now answer the same numbers on `driver-memory` that every SQL face and objectql's in-memory fallback already answered, instead of `null` and `0` (#11065).
+
+Measured on one `AnalyticsService.queryDataset` call, one dataset, one set of rows, run twice — five `crm_case` records, four closed (three with `is_sla_violated: false`, one `true`), one open with `true`:
+
+```
+[memory] unfiltered {"avg_sla_violated":null, "closed_count":4}
+[memory] closed-filter {"avg_sla_violated":null, "closed_count":4}
+[sqlite] unfiltered {"avg_sla_violated":0.4, "closed_count":4}
+[sqlite] closed-filter {"avg_sla_violated":0.25, "closed_count":4}
+```
+
+SQLite's are the arithmetically correct numbers (2/5 unfiltered, 1/4 over the closed cases). The `count` measures beside them agreed on both drivers, and so did a `derived` ratio built on those counts — the divergence was specific to averaging a boolean.
+
+**There were three implementations of "average a column" in play, and this driver was the lone outlier.** SQLite lowers `AVG(col)`; objectql's in-memory fallback (`in-memory-aggregation.ts`) coerces with `Number(v)`, and `Number(true) === 1`; `driver-memory` selected its aggregands with `typeof v === 'number'`, which drops every boolean, leaving `nums.length === 0` and returning `null`. So this is an alignment to the two faces that already agreed, not a new convention.
+
+**Both of this package's faces carried the defect independently**, and both are fixed:
+
+- the **data face** (`computeAggregate`, reached by `engine.aggregate` pushdown — the door the report's own repro takes) selected with `typeof v === 'number'`;
+- the **analytics face** (`buildAggregator`) emitted a bare mingo `$avg`, and mingo ignores a non-numeric value exactly as MongoDB does — measured at `{avg: null, sum: 0}` over the same five rows.
+
+Fixing one alone would have left the other free to keep its own answer, which is the shape of this package's recurring defect (#5374, #6814).
+
+**`sum` is aligned with `avg` deliberately.** The two share the data face's arm, and `SUM(bool)` is "how many true" on every SQL face and in the objectql fallback; correcting only the function the report named would have left the identical defect alive one function over, answering `0` for a column with two `true` rows.
+
+**The coercion is boolean-only, and the narrowness is the point.** `null`, a missing key and a non-numeric string reach the accumulators unchanged and stay excluded. Adopting the wider half of objectql's `toNumber` — which maps a non-numeric string to `0` — would average garbage as zero rather than excluding it; whether that is right is a separate question this change does not open, and a regression row pins the exclusion on both faces so it cannot arrive by accident.
+
+**Why it mattered beyond the number.** Neither face errors, so a dashboard tile bound to a rate measure rendered a percentage under SQL and a blank here, indistinguishable from "no matching rows". The test-facing half is worse: a suite pinning such a measure on the in-memory driver asserted against `null` and could not fail in the direction that matters. Nothing in the repo pinned the old value — the shared cross-driver fixture (`AGGREGATION_ROWS`) carries no boolean column at all, which is why every face could disagree here unobserved.

packages/drivers/driver-memory/src/memory-analytics.ts

@@ -480,6 +480,52 @@ function sizeDistinctSet(values: readonly unknown[]): number {
  return new Set(values.filter((v) => v !== null && v !== undefined)).size;
 }
 
+/**
+ * [#11065] `path`, with a BOOLEAN rendered as the number it is worth — the
+ * aggregand expression `$sum` and `$avg` consume on this face.
+ *
+ * ## What it is for
+ *
+ * mingo's `$avg` mirrors MongoDB's and IGNORES a non-numeric value, so a
+ * whole boolean column averaged to `null` and summed to `0` (measured: five
+ * bools in, `{avg: null, sum: 0}` out). Under SQL the same rows answer
+ * `AVG(col)` = 0.4 and `SUM(col)` = 2, and objectql's in-memory fallback
+ * (`in-memory-aggregation.ts`) answers those numbers too, because its
+ * `toNumber` is `Number(v)` and `Number(true) === 1`. A rate measure over a
+ * flag column — an SLA-violation rate, a win rate — is the ordinary shape of
+ * that query, and the two answers are not two spellings of one: a tile bound
+ * to the measure renders a percentage on one driver and a blank on the other,
+ * with no error on either path.
+ *
+ * ## Why an EXPRESSION and not post-processing
+ *
+ * The `count_distinct` neighbour above collects with `$addToSet` and sizes the
+ * array after `driver.aggregate` returns ({@link sizeDistinctSet}). Sum and
+ * average must NOT be built that way: the post-processing step runs after the
+ * pipeline's own `$sort` and `$limit` stages, so a measure left as an array
+ * until then would be SORTED as an array — `order` over a `sum` or `avg`
+ * measure is an ordinary analytics query, unlike ordering by `count_distinct`.
+ * Keeping the rule inside the `$group` expression leaves every later stage
+ * looking at the number it expects.
+ *
+ * ## The narrowness is deliberate
+ *
+ * Only `bool` is rewritten. Everything else — null, missing, a non-numeric
+ * string — reaches mingo exactly as before and is ignored by the accumulator
+ * exactly as before (measured: a numeric column carrying a null, a string and
+ * a missing key answers identically with and without this wrapper). Coercing
+ * wider would mean adopting `toNumber`'s other half, which maps a non-numeric
+ * string to `0` and so averages garbage as zero rather than excluding it —
+ * a separate question from this one.
+ *
+ * The data face carries the same rule in JavaScript (`memory-driver.ts`,
+ * `computeAggregate`); `memory-boolean-aggregand.test.ts` drives both, because
+ * one face aligned alone is how this package's faces come to disagree.
+ */
+function numericAggregandExpr(path: string): Record<string, unknown> {
+ return { $cond: [{ $eq: [{ $type: path }, 'bool'] }, { $cond: [path, 1, 0] }, path] };
+}
+
 /**
  * [#7853] A `JSON.stringify` replacer that renders a `RegExp` operand instead of
  * dropping it — the one value type the pipeline dump carries that
@@ -1192,9 +1238,9 @@ export class MemoryAnalyticsService implements IAnalyticsService {
  case 'count':
  return { $sum: 1 };
  case 'sum':
- return { $sum: `$${fieldPath}` };
+ return { $sum: numericAggregandExpr(`$${fieldPath}`) };
  case 'avg':
- return { $avg: `$${fieldPath}` };
+ return { $avg: numericAggregandExpr(`$${fieldPath}`) };
  case 'min':
  return { $min: `$${fieldPath}` };
  case 'max':