feat: add IS NULL/IS NOT NULL page skip via nullCount stats

- IS NULL skips pages with nullCount=0 (no nulls to find)
- IS NOT NULL skips pages with nullCount=rowCount (all nulls)
- Updated performance docs to list all 12 page-skip filter ops

Author: teamchong

docs/src/content/docs/performance.mdx

@@ -106,6 +106,8 @@ This is automatic — no configuration needed. Supported filter ops:
 | `not_in` | Uniform page (min = max) appears in NOT IN list |
 | `between` | Page range and filter range don't overlap |
 | `not_between` | Entire page range inside the excluded range |
+| `is_null` | Page has zero null values (nullCount = 0) |
+| `is_not_null` | Page is entirely null (nullCount = rowCount) |
 
 String columns also have min/max stats (lexicographic). `like` and `not_like` filters don't benefit from page skip.
 

src/decode.test.ts

@@ -180,6 +180,25 @@ describe("canSkipPage", () => {
   it("does not skip range page for NOT IN", () => {
     expect(canSkipPage(page, [{ column: "x", op: "not_in", value: [10, 50, 90] }], "x")).toBe(false);
   });
+
+  it("skips page with IS NULL when nullCount is 0", () => {
+    expect(canSkipPage(page, [{ column: "x", op: "is_null", value: 0 }], "x")).toBe(true);
+  });
+
+  it("does not skip page with IS NULL when nullCount > 0", () => {
+    const withNulls: PageInfo = { byteOffset: 0n, byteLength: 100, rowCount: 50, nullCount: 5, minValue: 10, maxValue: 90 };
+    expect(canSkipPage(withNulls, [{ column: "x", op: "is_null", value: 0 }], "x")).toBe(false);
+  });
+
+  it("skips page with IS NOT NULL when all rows are null", () => {
+    const allNull: PageInfo = { byteOffset: 0n, byteLength: 100, rowCount: 50, nullCount: 50 };
+    expect(canSkipPage(allNull, [{ column: "x", op: "is_not_null", value: 0 }], "x")).toBe(true);
+  });
+
+  it("does not skip page with IS NOT NULL when some rows are non-null", () => {
+    const withNulls: PageInfo = { byteOffset: 0n, byteLength: 100, rowCount: 50, nullCount: 5, minValue: 10, maxValue: 90 };
+    expect(canSkipPage(withNulls, [{ column: "x", op: "is_not_null", value: 0 }], "x")).toBe(false);
+  });
 });
 
 describe("assembleRows", () => {

src/decode.ts

@@ -9,7 +9,9 @@ import { decodeLanceV2Utf8 } from "./lance-v2.js";
 export function canSkipPage(page: PageInfo, filters: QueryDescriptor["filters"], columnName: string): boolean {
   for (const filter of filters) {
     if (filter.column !== columnName) continue;
-    if (filter.op === "is_null" || filter.op === "is_not_null") continue;
+    // is_null: skip when page has no nulls; is_not_null: skip when page is all nulls
+    if (filter.op === "is_null") { if (page.nullCount === 0) return true; continue; }
+    if (filter.op === "is_not_null") { if (page.nullCount === page.rowCount) return true; continue; }
     if (page.minValue === undefined || page.maxValue === undefined) continue;
 
     let { minValue: min, maxValue: max } = page;