fix(cache): avoid repeated copies when encoding query results

Refs: #9755

apps/desktop/src/lib/__tests__/tabs/tabResultCache.performance.spec.ts

@@ -0,0 +1,110 @@
+import { decode } from "@msgpack/msgpack";
+import { describe, expect, it, vi } from "vitest";
+import { decodeTabResultSnapshot, encodeTabResultSnapshot } from "@/lib/tabs/tabResultCache";
+import type { QueryResult } from "@/types/database";
+
+function createResult(rowCount: number): QueryResult {
+  return {
+    columns: ["id", "name", "enabled"],
+    rows: Array.from({ length: rowCount }, (_, index) => [index, `row-${index}`, index % 2 === 0]),
+    affected_rows: 0,
+    execution_time_ms: 1,
+  };
+}
+
+describe("result cache serialization work", () => {
+  it.each([
+    { columns: [], rows: [] },
+    { columns: [], rows: [[]] },
+    { columns: ["first", "second"], rows: [[1], []] },
+  ])("preserves empty and ragged result shapes: %j", ({ columns, rows }) => {
+    const encoded = encodeTabResultSnapshot({ result: { columns, rows, affected_rows: 0, execution_time_ms: 0 }, cachedAt: 1 });
+    expect(decodeTabResultSnapshot(encoded)?.result?.rows).toEqual(rows.map((row) => columns.map((_, columnIndex) => row[columnIndex] ?? null)));
+  });
+
+  it("does not repeatedly copy column vectors while cleaning optional metadata", () => {
+    const rowCount = 1000;
+    const result = createResult(rowCount);
+    let fullLengthMaps = 0;
+    const originalMap = Array.prototype.map;
+    const mapSpy = vi.spyOn(Array.prototype, "map").mockImplementation(function (this: unknown[], callback, thisArg) {
+      if (this.length === rowCount) fullLengthMaps += 1;
+      return originalMap.call(this, callback, thisArg);
+    });
+    let encoded: Uint8Array;
+    try {
+      encoded = encodeTabResultSnapshot({ result, cachedAt: 1 });
+    } finally {
+      mapSpy.mockRestore();
+    }
+
+    expect(fullLengthMaps).toBeLessThanOrEqual(result.columns.length);
+    expect(decodeTabResultSnapshot(encoded)?.result?.rows).toEqual(result.rows);
+  });
+
+  it("reads each source row once when converting a wide result to columns", () => {
+    const result = createResult(100);
+    let rowReads = 0;
+    result.rows = new Proxy(result.rows, {
+      get(target, property, receiver) {
+        if (typeof property === "string" && /^\d+$/.test(property)) rowReads += 1;
+        return Reflect.get(target, property, receiver);
+      },
+    });
+
+    const encoded = encodeTabResultSnapshot({ result, cachedAt: 1 });
+
+    expect(rowReads).toBe(result.rows.length);
+    expect(decodeTabResultSnapshot(encoded)?.result?.rows).toEqual(createResult(100).rows);
+  });
+
+  it("preserves the version-1 payload and metadata cleanup for results and saved runs", () => {
+    const result = createResult(2);
+    result.rows = [
+      [1, "", false],
+      [2, null, true],
+    ];
+    result.session_id = "live-session";
+    result.mongo_documents = [{ retained: null, omitted: undefined, nested: { empty: undefined, values: [null, undefined, 0] }, date: new Date(0) }];
+    const encoded = encodeTabResultSnapshot({
+      result,
+      results: [result],
+      resultRuns: [{ id: "run-1", title: "Run 1", sequence: 1, sql: "select 1", createdAt: 1, result, results: [result] }],
+      cachedAt: 1,
+    });
+    const envelope = decode(encoded) as any;
+    const expectedResult = {
+      columns: ["id", "name", "enabled"],
+      columnValues: [
+        [1, 2],
+        ["", null],
+        [false, true],
+      ],
+      rowCount: 2,
+      mongo_documents: [{ retained: null, nested: { values: [null, null, 0] }, date: {} }],
+      affected_rows: 0,
+      execution_time_ms: 1,
+    };
+
+    expect(envelope).toEqual({
+      magic: "DBX_TAB_RESULT_CACHE",
+      version: 1,
+      codec: "msgpack-columnar",
+      cachedAt: 1,
+      rowCount: 2,
+      columnCount: 3,
+      payload: {
+        result: expectedResult,
+        results: [expectedResult],
+        resultRuns: [{ id: "run-1", title: "Run 1", sequence: 1, sql: "select 1", createdAt: 1, result: expectedResult, results: [expectedResult] }],
+        cachedAt: 1,
+      },
+    });
+    expect(result.rows).toEqual([
+      [1, "", false],
+      [2, null, true],
+    ]);
+    expect(result.mongo_documents[0]).toHaveProperty("omitted", undefined);
+    expect(result.session_id).toBe("live-session");
+  });
+});

apps/desktop/src/lib/tabs/tabResultCache.ts

@@ -388,8 +388,19 @@ function stripResultRunSessionIds(resultRuns: QueryTab["resultRuns"]): QueryTab[
 
 function toColumnarResult(result: QueryResult | undefined): ColumnarQueryResult | undefined {
   if (!result) return undefined;
-  const columnValues = result.columns.map((_, colIndex) => result.rows.map((row) => row[colIndex] ?? null));
-  return removeUndefinedFields({
+  const rowCount = result.rows.length;
+  const columnValues = result.columns.map(() => {
+    const values: CellValue[] = [];
+    values.length = rowCount;
+    return values;
+  });
+  for (let rowIndex = 0; rowIndex < rowCount; rowIndex++) {
+    const row = result.rows[rowIndex];
+    for (let columnIndex = 0; columnIndex < columnValues.length; columnIndex++) {
+      columnValues[columnIndex][rowIndex] = row?.[columnIndex] ?? null;
+    }
+  }
+  const metadata = removeUndefinedFields({
     columns: [...result.columns],
     execution_error: result.execution_error,
     statement_index: result.statement_index,
@@ -398,8 +409,7 @@ function toColumnarResult(result: QueryResult | undefined): ColumnarQueryResult
     spatial_columns: result.spatial_columns?.map((entry) => ({ column_index: entry.column_index, srid: entry.srid })),
     spatial_values: result.spatial_values?.map((row) => [...row]),
     large_value_cells: result.large_value_cells?.map((cell) => ({ ...cell })),
-    columnValues,
-    rowCount: result.rows.length,
+    rowCount,
     mongo_documents: result.mongo_documents ? clonePlain(result.mongo_documents) : undefined,
     mongo_copy_documents: result.mongo_copy_documents ? clonePlain(result.mongo_copy_documents) : undefined,
     affected_rows: result.affected_rows,
@@ -413,6 +423,7 @@ function toColumnarResult(result: QueryResult | undefined): ColumnarQueryResult
     sourceFrom: result.sourceFrom,
     sourceTo: result.sourceTo,
   });
+  return { ...metadata, columnValues };
 }
 
 function fromColumnarResult(result: ColumnarQueryResult | undefined): QueryResult | undefined {
@@ -445,18 +456,17 @@ function fromColumnarResult(result: ColumnarQueryResult | undefined): QueryResul
 }
 
 function snapshotToPayload(snapshot: TabResultSnapshot): TabResultSnapshotPayload {
-  return removeUndefinedFields({
-    ...snapshot,
-    result: toColumnarResult(snapshot.result),
-    results: snapshot.results?.map((result) => toColumnarResult(result)!),
-    resultRuns: snapshot.resultRuns?.map((run) =>
-      removeUndefinedFields({
-        ...run,
-        result: toColumnarResult(run.result),
-        results: run.results?.map((result) => toColumnarResult(result)!),
-      }),
-    ),
-  });
+  const { result, results, resultRuns, ...metadata } = snapshot;
+  return {
+    ...removeUndefinedFields(metadata),
+    result: toColumnarResult(result),
+    results: results?.map((result) => toColumnarResult(result)!),
+    resultRuns: resultRuns?.map(({ result, results, ...run }) => ({
+      ...removeUndefinedFields(run),
+      result: toColumnarResult(result),
+      results: results?.map((result) => toColumnarResult(result)!),
+    })),
+  };
 }
 
 function payloadToSnapshot(payload: TabResultSnapshotPayload): TabResultSnapshot {
@@ -725,7 +735,7 @@ export function encodeTabResultSnapshot(snapshot: TabResultSnapshot): Uint8Array
     columnCount: stats.columnCount,
     payload: snapshotToPayload(snapshot),
   };
-  return encode(removeUndefinedFields(envelope));
+  return encode(envelope, { ignoreUndefined: true });
 }
 
 export function decodeTabResultSnapshot(bytes: Uint8Array | ArrayBuffer): TabResultSnapshot | undefined {