feat(node): accept ArrayBuffer, Blob/File, and URL as blob column inputs (#4313)

Closes #4270.

## Summary

Blob v2 columns now accept more of the containers TypeScript code
commonly has, both as the column value and inside `{ data }` / `{ uri
}`:

| Input | Handling |
|---|---|
| `ArrayBuffer` | `new Uint8Array(value)`, no copy |
| `URL` | stored as `value.href` |
| `Blob` / `File` | `await value.arrayBuffer()` in the async write
paths: `createTable`, `add`, `mergeInsert` |

`makeArrowTable` is synchronous, so it can't read a `Blob`. Given one,
it throws an error that names the field and row and points to the async
APIs or `new Uint8Array(await value.arrayBuffer())`. It does not write a
null blob.

### Types
`BlobInput` is now the accepted input type. It is widened to the types
above and exported from the package entry point with `BlobData` and
`BlobUri`, so callers can annotate rows and `tsc` catches bad inputs.
The struct forms are a union that requires exactly one of `data` /
`uri`. The old normalized `{ data, uri }` shape is renamed to
`BlobValue` (internal).

### Implementation
- `blob.ts`: `normalizeBlobInput` (sync: `ArrayBuffer`/`URL`),
`resolveBlobInput` (async: `Blob`/`File`). `coerceBlobValue` normalizes
first.
- `arrow.ts`: `mapBlobInputs` walks only the blob positions in the
schema, including blobs nested in structs and lists. It copies records
and arrays only where a value changed, so caller data is never mutated.
`resolveBlobInputs` runs before `makeArrowTable` in `convertToTable`
(used by `add` / `mergeInsert`) and in `createTable`. Each distinct
`Blob` is read once.
- `makeArrowTable` now coerces every blob value to the full `{ data, uri
}` struct **before** schema inference. This also fixes two bugs that
existed before this change:
  - Rows mixing plain bytes with `{ data }` failed inference.
- A `{ uri }`-only struct produced a blob struct missing its `data`
child.

  Blob validation errors now include the field path and row.
- Also fixed along the way:
- `add` / `mergeInsert` on a table with an embedding function rejected
most blob values, because `ensureNestedFieldsExist` filled blob columns
in like ordinary structs. It now skips them.
- With a schema, a struct field that is `null` in one row and a record
in a later row failed inference. Primitives and arrays given for a
struct field are now rejected instead of being written as an all-null
struct.
- Blob structs with keys other than `data` / `uri` are rejected, which
catches typos. Class instances with `data` / `uri` are handled like
plain objects.

## Testing
- Unit tests in `__test__/blob.test.ts`: coercion of the new types,
rejection and error messages for `Blob` in the sync path, nested lists
and structs, `resolveBlobInputs` (only blob columns touched, caller data
untouched, shared `Blob` read once).
- Table tests in `__test__/table.test.ts`:
- `createTable`, `add`, and `mergeInsert` round-trip `ArrayBuffer` /
`Blob` / `File` bytes through `fetchBlobs`.
- `URL` and `{ uri: URL }` are added to the external-blob round-trip
test from #4317 (`allowExternalBlobOutsideBases`).
- Full `jest` suite passes locally after the rebase (938 passed). `pnpm
lint` is clean and `pnpm run docs` has been regenerated.

Streaming inputs (`ReadableStream`, Node `Readable`, async iterables)
remain out of scope, as the issue says.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

https://claude.ai/code/session_012U4KdHofT5edv3LcXHXbLv

---------

Co-authored-by: Claude <noreply@anthropic.com>

docs/src/js/globals.md

@@ -157,9 +157,12 @@
 
 - [AnalyzePlanDistributedMetrics](type-aliases/AnalyzePlanDistributedMetrics.md)
 - [BaseTokenizer](type-aliases/BaseTokenizer.md)
+- [BlobData](type-aliases/BlobData.md)
+- [BlobInput](type-aliases/BlobInput.md)
 - [BlobOptions](type-aliases/BlobOptions.md)
 - [BlobRange](type-aliases/BlobRange.md)
 - [BlobReadOptions](type-aliases/BlobReadOptions.md)
+- [BlobUri](type-aliases/BlobUri.md)
 - [Data](type-aliases/Data.md)
 - [DataLike](type-aliases/DataLike.md)
 - [DataTypeLike](type-aliases/DataTypeLike.md)

docs/src/js/type-aliases/BlobData.md

@@ -0,0 +1,16 @@
+[**@lancedb/lancedb**](../README.md) • **Docs**
+
+***
+
+[@lancedb/lancedb](../globals.md) / BlobData
+
+# Type Alias: BlobData
+
+```ts
+type BlobData: Buffer | Uint8Array | ArrayBuffer | Blob;
+```
+
+Bytes accepted for a blob value. `ArrayBuffer` is wrapped without copying.
+`Blob` and `File` are read with `arrayBuffer()`, which only the async write
+paths ([Connection.createTable](../classes/Connection.md#createtable), [Table.add](../classes/Table.md#add),
+[Table.mergeInsert](../classes/Table.md#mergeinsert)) can do.

docs/src/js/type-aliases/BlobInput.md

@@ -0,0 +1,36 @@
+[**@lancedb/lancedb**](../README.md) • **Docs**
+
+***
+
+[@lancedb/lancedb](../globals.md) / BlobInput
+
+# Type Alias: BlobInput
+
+```ts
+type BlobInput:
+  | BlobData
+  | BlobUri
+  | object
+  | object
+  | null
+  | undefined;
+```
+
+A value accepted for a `lance.blob.v2` column (see [blob](../functions/blob.md)).
+
+Either inline bytes, a URI pointing at external bytes, or a struct that sets
+exactly one of `data` or `uri`. `null` and `undefined` write a null blob.
+
+## Example
+
+```ts
+import { pathToFileURL } from "node:url";
+import type { BlobInput } from "@lancedb/lancedb";
+
+const rows: { id: bigint; image: BlobInput }[] = [
+  { id: 1n, image: await (await fetch(url)).arrayBuffer() },
+  { id: 2n, image: pathToFileURL("/data/cat.png") },
+  { id: 3n, image: { data: new Blob(["hello"]) } },
+];
+await table.add(rows);
+```

docs/src/js/type-aliases/BlobUri.md

@@ -0,0 +1,13 @@
+[**@lancedb/lancedb**](../README.md) • **Docs**
+
+***
+
+[@lancedb/lancedb](../globals.md) / BlobUri
+
+# Type Alias: BlobUri
+
+```ts
+type BlobUri: string | URL;
+```
+
+A URI accepted for a blob value. A `URL` is stored as its `href`.

nodejs/__test__/arrow.test.ts

@@ -790,6 +790,43 @@ describe.each(arrowVersions)("Arrow %#", (arrow: ApacheArrow) => {
       }
     });
 
+    it("will allow null values around struct values with a schema", function () {
+      const schema = new Schema([
+        new Field("value", new Struct([new Field("nested", new Int32())])),
+      ]);
+      for (const { records, nullIndex } of [
+        {
+          records: [{ value: null }, { value: { nested: 2 } }],
+          nullIndex: 0,
+        },
+        {
+          records: [{ value: { nested: 1 } }, { value: null }],
+          nullIndex: 1,
+        },
+      ]) {
+        const table = makeArrowTable(records, { schema });
+        const values = table.getChild("value");
+
+        expect(values?.nullCount).toBe(1);
+        expect(values?.get(nullIndex)).toBeNull();
+      }
+    });
+
+    it("will reject non-object values for struct fields in a schema", function () {
+      const schema = new Schema([
+        new Field("value", new Struct([new Field("nested", new Int32())])),
+      ]);
+      for (const records of [
+        [{ value: 5 }],
+        [{ value: 5 }, { value: { nested: 1 } }],
+        [{ value: { nested: 1 } }, { value: "oops" }],
+      ]) {
+        expect(() => makeArrowTable(records, { schema })).toThrow(
+          /Expected a struct value for field value at row \d, got/,
+        );
+      }
+    });
+
     it("will allow a schema to be provided", async function () {
       await checkTableCreation(
         async (records, _, schema) =>

nodejs/__test__/blob.test.ts

@@ -1,9 +1,25 @@
 // SPDX-License-Identifier: Apache-2.0
 // SPDX-FileCopyrightText: Copyright The LanceDB Authors
 
-import { Field, Int64, List, Schema, Struct, Utf8 } from "apache-arrow";
+import {
-import { makeArrowTable } from "../lancedb/arrow";
+  Field,
+  Float,
+  Float32,
+  Int32,
+  Int64,
+  List,
+  Schema,
+  Struct,
+  Utf8,
+} from "apache-arrow";
+import {
+  convertToTable,
+  makeArrowTable,
+  resolveBlobInputs,
+} from "../lancedb/arrow";
 import { BlobFile, blob, coerceBlobValue, isBlobField } from "../lancedb/blob";
+import { EmbeddingFunction, LanceSchema } from "../lancedb/embedding";
+import { getRegistry } from "../lancedb/embedding/registry";
 
 describe("blob()", () => {
   it("marks the field as lance.blob.v2", () => {
@@ -46,6 +62,13 @@ describe("blob()", () => {
   });
 });
 
+class BlobStruct {
+  constructor(
+    public data?: unknown,
+    public uri?: unknown,
+  ) {}
+}
+
 describe("coerceBlobValue", () => {
   it.each([
     ["Buffer", Buffer.from("x"), { data: Buffer.from("x"), uri: null }],
@@ -65,6 +88,41 @@ describe("coerceBlobValue", () => {
       { uri: "s3://bucket/key" },
       { data: null, uri: "s3://bucket/key" },
     ],
+    [
+      "ArrayBuffer",
+      new Uint8Array([120]).buffer,
+      { data: new Uint8Array([120]), uri: null },
+    ],
+    [
+      "URL",
+      new URL("https://example.com/blob"),
+      { data: null, uri: "https://example.com/blob" },
+    ],
+    [
+      "data struct with ArrayBuffer",
+      { data: new Uint8Array([121]).buffer },
+      { data: new Uint8Array([121]), uri: null },
+    ],
+    [
+      "uri struct with URL",
+      { uri: new URL("file:///tmp/a.png") },
+      { data: null, uri: "file:///tmp/a.png" },
+    ],
+    [
+      "class instance with Uint8Array data",
+      new BlobStruct(new Uint8Array([122])),
+      { data: new Uint8Array([122]), uri: null },
+    ],
+    [
+      "class instance with ArrayBuffer data",
+      new BlobStruct(new Uint8Array([122]).buffer),
+      { data: new Uint8Array([122]), uri: null },
+    ],
+    [
+      "class instance with URL uri",
+      new BlobStruct(undefined, new URL("s3://bucket/key")),
+      { data: null, uri: "s3://bucket/key" },
+    ],
     ["null", null, null],
   ])("accepts %s", (_name, input, expected) => {
     expect(coerceBlobValue(input)).toEqual(expected);
@@ -76,7 +134,7 @@ describe("coerceBlobValue", () => {
     [
       "Int16Array",
       new Int16Array([1]),
-      /Blob data must be Buffer or Uint8Array/,
+      /Blob data must be Buffer, Uint8Array, ArrayBuffer, or Blob/,
     ],
     [
       "both data and uri",
@@ -88,11 +146,160 @@ describe("coerceBlobValue", () => {
       { data: null, uri: null },
       /exactly one of 'data' or 'uri'/,
     ],
+    ["Blob", new Blob(["x"]), /must be read asynchronously/],
+    ["data struct with Blob", { data: new Blob(["x"]) }, /asynchronously/],
+    [
+      "class instance with Blob data",
+      new BlobStruct(new Blob(["x"])),
+      /asynchronously/,
+    ],
+    [
+      "unknown struct field",
+      { data: Buffer.from("y"), mime: "image/png" },
+      /Blob struct values only support 'data' and 'uri', got 'mime'/,
+    ],
+    [
+      "misspelled struct field",
+      { uri: "s3://bucket/key", dat: Buffer.from("y") },
+      /got 'dat'/,
+    ],
+    [
+      "SharedArrayBuffer",
+      new SharedArrayBuffer(2),
+      /Blob column values must be Buffer, Uint8Array, ArrayBuffer, Blob/,
+    ],
+    ["Date", new Date(0), /Blob column values must be/],
   ])("rejects %s", (_name, input, message) => {
     expect(() => coerceBlobValue(input)).toThrow(message);
   });
 });
 
+describe("resolveBlobInputs", () => {
+  it("reads Blob and File values in blob columns only", async () => {
+    const schema = new Schema([
+      new Field("name", new Utf8(), true),
+      blob("image"),
+      new Field("images", new List(blob("image")), true),
+    ]);
+    const shared = new Blob(["same"]);
+    const notABlobColumn = new Blob(["other"]);
+    const data = [
+      {
+        name: notABlobColumn,
+        image: new File(["file"], "a.txt"),
+        images: [shared, { data: shared }, null],
+      },
+      { name: "x", image: Buffer.from("buf"), images: null },
+    ];
+    const resolved = await resolveBlobInputs(data, schema);
+
+    expect(resolved[0].name).toBe(notABlobColumn);
+    expect(Buffer.from(resolved[0].image as Uint8Array).toString()).toBe(
+      "file",
+    );
+    const images = resolved[0].images as [Uint8Array, { data: Uint8Array }];
+    expect(Buffer.from(images[0]).toString()).toBe("same");
+    expect(Buffer.from(images[1].data).toString()).toBe("same");
+    // Rows without Blob values and the caller's records are left alone.
+    expect(resolved[1]).toBe(data[1]);
+    expect(data[0].images?.[0]).toBe(shared);
+  });
+
+  it("reads each distinct Blob once, bare or inside data structs", async () => {
+    class CountingBlob extends Blob {
+      calls = 0;
+      async arrayBuffer(): Promise<ArrayBuffer> {
+        this.calls++;
+        return super.arrayBuffer();
+      }
+    }
+    const shared = new CountingBlob(["same"]);
+    const schema = new Schema([blob("image")]);
+    const resolved = await resolveBlobInputs(
+      [
+        { image: { data: shared } },
+        { image: { data: shared } },
+        { image: shared },
+      ],
+      schema,
+    );
+    expect(shared.calls).toBe(1);
+    const first = (resolved[0].image as { data: Uint8Array }).data;
+    expect(Buffer.from(first).toString()).toBe("same");
+    expect((resolved[1].image as { data: Uint8Array }).data).toBe(first);
+    expect(resolved[2].image).toBe(first);
+  });
+
+  it("reads a Blob held by a class instance", async () => {
+    const schema = new Schema([blob("image")]);
+    const [row] = await resolveBlobInputs(
+      [{ image: new BlobStruct(new Blob(["hi"])) }],
+      schema,
+    );
+    expect(
+      Buffer.from((row.image as { data: Uint8Array }).data).toString(),
+    ).toBe("hi");
+  });
+
+  it("returns the input when there is nothing to read", async () => {
+    const data = [{ image: Buffer.from("x") }];
+    const schema = new Schema([blob("image")]);
+    await expect(resolveBlobInputs(data, schema)).resolves.toBe(data);
+    await expect(resolveBlobInputs(data)).resolves.toBe(data);
+  });
+});
+
+describe("convertToTable blob columns with embedding functions", () => {
+  // Embedding metadata routes rows through ensureNestedFieldsExist, which must
+  // leave blob values for the blob coercion instead of treating them as structs.
+  class LengthEmbedding extends EmbeddingFunction<string> {
+    ndims() {
+      return 2;
+    }
+    embeddingDataType(): Float {
+      return new Float32();
+    }
+    async computeSourceEmbeddings(data: string[]) {
+      return data.map((text) => [text.length, 1]);
+    }
+  }
+  getRegistry().register("blob-test-length")(LengthEmbedding);
+  const func = getRegistry().get<LengthEmbedding>("blob-test-length")!.create();
+  const embeddingSchema = LanceSchema({
+    text: func.sourceField(new Utf8()),
+    vector: func.vectorField(),
+  });
+  const schema = new Schema(
+    [...embeddingSchema.fields, blob("image")],
+    embeddingSchema.metadata,
+  );
+
+  it.each([
+    ["Uint8Array", new Uint8Array([104, 105]), "hi", null],
+    ["ArrayBuffer", new Uint8Array([104, 105]).buffer, "hi", null],
+    ["Blob", new Blob(["hi"]), "hi", null],
+    ["URI string", "s3://b/k", null, "s3://b/k"],
+    ["URL", new URL("s3://b/k"), null, "s3://b/k"],
+    ["data struct", { data: new Uint8Array([104, 105]) }, "hi", null],
+  ])("accepts %s input", async (_name, image, data, uri) => {
+    const table = await convertToTable([{ text: "a", image }], undefined, {
+      schema,
+    });
+    const column = table.getChild("image")!;
+    expect(column.nullCount).toBe(0);
+    const bytes = column.getChild("data")!.get(0);
+    expect(bytes == null ? null : Buffer.from(bytes).toString()).toBe(data);
+    expect(column.getChild("uri")!.get(0)).toBe(uri);
+  });
+
+  it("writes a missing blob as null", async () => {
+    const table = await convertToTable([{ text: "a" }], undefined, { schema });
+    const column = table.getChild("image")!;
+    expect(column.nullCount).toBe(1);
+    expect(column.get(0)).toBeNull();
+  });
+});
+
 describe("BlobFile", () => {
   it("rejects constructing BlobFile without a native handle", () => {
     expect(() => new (BlobFile as unknown as { new (): BlobFile })()).toThrow(
@@ -103,26 +310,122 @@ describe("BlobFile", () => {
 
 describe("makeArrowTable blob columns", () => {
   it.each([
-    ["ArrayBuffer", new Uint8Array([104]).buffer],
-    ["Blob", new Blob(["hello"])],
-    ["File", new File(["hello"], "hello.txt")],
-    ["URL", new URL("https://example.com/blob")],
     ["ReadableStream", new ReadableStream()],
-    ["data struct with ArrayBuffer", { data: new Uint8Array([104]).buffer }],
+    ["Int16Array", new Int16Array([1])],
-    ["uri struct with URL", { uri: new URL("https://example.com/blob") }],
   ])("rejects %s input rather than writing a null blob", (_name, image) => {
     const schema = new Schema([blob("image")]);
     expect(() => makeArrowTable([{ image }], { schema })).toThrow(/image/);
   });
 
-  it("rejects Blob instances with enumerable fields as one invalid value", () => {
+  it.each([
+    ["Blob", new Blob(["hello"])],
+    ["File", new File(["hello"], "hello.txt")],
+    ["data struct with Blob", { data: new Blob(["hello"]) }],
+    [
+      "Blob with enumerable fields",
+      Object.assign(new Blob(["hello"]), { position: 0 }),
+    ],
+  ])("points %s input at the async APIs", (_name, image) => {
     const schema = new Schema([blob("image")]);
-    const image = Object.assign(new Blob(["hello"]), { position: 0 });
+    expect(() => makeArrowTable([{ id: 1, image }], { schema })).toThrow(
-    expect(() => makeArrowTable([{ image }], { schema })).toThrow(
+      /blob field image at row 0: Blob and File values must be read asynchronously/,
-      "Unsupported object value for field image at row 0.",
     );
   });
 
+  it.each([
+    ["ArrayBuffer", new Uint8Array([104, 105]).buffer, "hi", null],
+    [
+      "data struct with ArrayBuffer",
+      { data: new Uint8Array([104, 105]).buffer },
+      "hi",
+      null,
+    ],
+    ["URL", new URL("https://example.com/a"), null, "https://example.com/a"],
+    [
+      "uri struct with URL",
+      { uri: new URL("file:///tmp/a.png") },
+      null,
+      "file:///tmp/a.png",
+    ],
+  ])("accepts %s input", (_name, image, data, uri) => {
+    const schema = new Schema([blob("image")]);
+    const input = { image };
+    const table = makeArrowTable([input], { schema });
+    const column = table.getChild("image")!;
+    expect(column.nullCount).toBe(0);
+    const bytes = column.getChild("data")!.get(0);
+    expect(bytes == null ? null : Buffer.from(bytes).toString()).toBe(data);
+    expect(column.getChild("uri")!.get(0)).toBe(uri);
+    // The caller's record is left untouched.
+    expect(input.image).toBe(image);
+  });
+
+  it.each([
+    ["Uint8Array", new Uint8Array([104, 105]), "hi", null],
+    ["URI string", "s3://b/k", null, "s3://b/k"],
+    ["data struct", { data: new Uint8Array([104, 105]) }, "hi", null],
+  ])("accepts %s input after a null row", (_name, image, data, uri) => {
+    const schema = new Schema([blob("image")]);
+    const table = makeArrowTable([{ image: null }, { image }], { schema });
+    const column = table.getChild("image")!;
+    expect(column.nullCount).toBe(1);
+    expect(column.get(0)).toBeNull();
+    const bytes = column.getChild("data")!.get(1);
+    expect(bytes == null ? null : Buffer.from(bytes).toString()).toBe(data);
+    expect(column.getChild("uri")!.get(1)).toBe(uri);
+  });
+
+  it("accepts a null struct before one holding a blob", () => {
+    const schema = new Schema([
+      new Field("info", new Struct([blob("image")]), true),
+    ]);
+    const table = makeArrowTable(
+      [{ info: null }, { info: { image: new Uint8Array([97]) } }],
+      { schema },
+    );
+    const info = table.getChild("info")!;
+    expect(info.get(0)).toBeNull();
+    const image = (info.get(1) as { image: { data: Uint8Array } }).image;
+    expect(Buffer.from(image.data).toString()).toBe("a");
+  });
+
+  it("skips a missing blob column named like an Object.prototype member", () => {
+    const schema = new Schema([
+      new Field("id", new Int32(), true),
+      blob("constructor"),
+    ]);
+    const table = makeArrowTable([{ id: 1 }], { schema });
+    expect(table.schema.fields.map((f) => f.name)).toEqual(["id"]);
+  });
+
+  it("accepts ArrayBuffer and URL inside lists and structs", () => {
+    const schema = new Schema([
+      new Field("images", new List(blob("image")), true),
+      new Field("info", new Struct([blob("image")]), true),
+    ]);
+    const table = makeArrowTable(
+      [
+        {
+          images: [new Uint8Array([97]).buffer, new URL("s3://b/k")],
+          info: { image: new Uint8Array([98]).buffer },
+        },
+      ],
+      { schema },
+    );
+    const images = Array.from(
+      table.getChild("images")!.get(0) as Iterable<{
+        data: Uint8Array | null;
+        uri: string | null;
+      }>,
+    );
+    expect(Buffer.from(images[0].data!).toString()).toBe("a");
+    expect(images[1].uri).toBe("s3://b/k");
+    const info = table.getChild("info")!.get(0) as {
+      image: { data: Uint8Array };
+    };
+    expect(Buffer.from(info.image.data).toString()).toBe("b");
+  });
+
   it("coerces Buffer input onto a blob field", () => {
     const schema = new Schema([
       new Field("id", new Int64(), true),

nodejs/__test__/table.test.ts

@@ -9,6 +9,7 @@ import * as tmp from "tmp";
 
 import {
   AutoQuery,
+  type BlobInput,
   Connection,
   MatchQuery,
   PhraseQuery,
@@ -2583,7 +2584,7 @@ describe("when dealing with blob columns", () => {
       new Field("id", new Int64(), true),
       blob("image"),
     ]);
-    const row = { id: 1n, image: new Uint8Array([104]).buffer };
+    const row = { id: 1n, image: new ReadableStream() };
 
     await expect(db.createTable("invalid", [row], { schema })).rejects.toThrow(
       /field image at row 0/,
@@ -2613,6 +2614,8 @@ describe("when dealing with blob columns", () => {
   it.each([
     ["URI string", (uri: string) => uri],
     ["URI struct", (uri: string) => ({ uri })],
+    ["URL", (uri: string) => new URL(uri)],
+    ["URL struct", (uri: string) => ({ uri: new URL(uri) })],
   ])(
     "round-trips an external blob from a %s after reopening",
     async (_label, blobValue) => {
@@ -2706,6 +2709,63 @@ describe("when dealing with blob columns", () => {
     expect(bytes[0]).toEqual(payload);
   });
 
+  it("accepts ArrayBuffer, Blob, and File in createTable and add", async () => {
+    const db = await connect(tmpDir.name);
+    const schema = new Schema([
+      new Field("id", new Int64(), true),
+      blob("image"),
+    ]);
+    const rows: { id: bigint; image: BlobInput }[] = [
+      { id: 1n, image: new TextEncoder().encode("array-buffer").buffer },
+      { id: 2n, image: new Blob(["blob"]) },
+      { id: 3n, image: { data: new File(["file"], "f.txt") } },
+    ];
+    const table = await db.createTable("widened", rows.slice(0, 2), {
+      schema,
+    });
+    await table.add(rows.slice(2));
+
+    const results = await table.query().select(["id"]).withRowId().toArray();
+    results.sort((a, b) => Number(a.id - b.id));
+    const bytes = await table.fetchBlobs(
+      "image",
+      results.map((row) => row._rowid as bigint),
+    );
+    expect(bytes.map((b) => b?.toString())).toEqual([
+      "array-buffer",
+      "blob",
+      "file",
+    ]);
+  });
+
+  it("accepts Blob values in mergeInsert", async () => {
+    const db = await connect(tmpDir.name);
+    const schema = new Schema([
+      new Field("id", new Int64(), true),
+      blob("image"),
+    ]);
+    const table = await db.createTable(
+      "merge_blobs",
+      [{ id: 1n, image: Buffer.from("old") }],
+      { schema },
+    );
+    await table
+      .mergeInsert("id")
+      .whenMatchedUpdateAll()
+      .whenNotMatchedInsertAll()
+      .execute([
+        { id: 1n, image: new Blob(["new"]) },
+        { id: 2n, image: new Uint8Array([104, 105]).buffer },
+      ]);
+    const results = await table.query().select(["id"]).withRowId().toArray();
+    results.sort((a, b) => Number(a.id - b.id));
+    const bytes = await table.fetchBlobs(
+      "image",
+      results.map((row) => row._rowid as bigint),
+    );
+    expect(bytes.map((b) => b?.toString())).toEqual(["new", "hi"]);
+  });
+
   it("discovers blob columns", async () => {
     const { table } = await openBlobTable();
     expect(await table.blobColumns()).toEqual(["image"]);

nodejs/lancedb/arrow.ts

@@ -40,7 +40,12 @@ import {
 } from "apache-arrow";
 import { Buffers } from "apache-arrow/data";
 import { typedArrayToArrowType } from "./arrow_type";
-import { coerceBlobValue, isBlobField } from "./blob";
+import {
+  blobToRead,
+  coerceBlobValue,
+  isBlobField,
+  withBlobBytes,
+} from "./blob";
 import { type EmbeddingFunction } from "./embedding/embedding_function";
 import {
   EmbeddingFunctionConfig,
@@ -449,6 +454,24 @@ export function makeArrowTable(
     );
   }
 
+  if (schema !== undefined) {
+    // Validate blob values up front and give every one the full
+    // `{ data, uri }` shape, so inference sees the same struct whether a row
+    // passed bytes, a URI, or a partial struct.
+    data = mapBlobInputs(data, schema, (value, field, row) => {
+      if (value === undefined) {
+        return value;
+      }
+      try {
+        return coerceBlobValue(value);
+      } catch (e) {
+        throw new Error(
+          `Invalid value for blob field ${field} at row ${row}: ${(e as Error).message}`,
+        );
+      }
+    });
+  }
+
   let schemaMetadata = schema?.metadata || new Map<string, string>();
   if (metadata !== undefined) {
     schemaMetadata = new Map([...schemaMetadata, ...metadata]);
@@ -510,6 +533,133 @@ function containsBlobField(field: Field): boolean {
   );
 }
 
+type BlobInputVisitor = (value: unknown, field: string, row: number) => unknown;
+
+/**
+ * Calls `visit` on every value that lands in a blob column of `schema`,
+ * including blobs nested in structs and lists, and replaces it with the
+ * result. Records and arrays are copied only where a value changed, so the
+ * caller's data is never mutated.
+ */
+function mapBlobInputs(
+  data: Array<Record<string, unknown>>,
+  schema: Schema,
+  visit: BlobInputVisitor,
+): Array<Record<string, unknown>> {
+  if (!schema.fields.some(containsBlobField)) {
+    return data;
+  }
+  return data.map((record, row) =>
+    isObject(record)
+      ? mapBlobFields(record, schema.fields, "", row, visit)
+      : record,
+  );
+}
+
+function mapBlobFields(
+  record: Record<string, unknown>,
+  fields: Field[],
+  prefix: string,
+  row: number,
+  visit: BlobInputVisitor,
+): Record<string, unknown> {
+  let out: Record<string, unknown> | undefined;
+  for (const field of fields) {
+    if (!containsBlobField(field) || !Object.hasOwn(record, field.name)) {
+      continue;
+    }
+    const value = record[field.name];
+    const mapped = mapBlobField(
+      value,
+      field,
+      `${prefix}${field.name}`,
+      row,
+      visit,
+    );
+    if (mapped !== value) {
+      out ??= { ...record };
+      out[field.name] = mapped;
+    }
+  }
+  return out ?? record;
+}
+
+function mapBlobField(
+  value: unknown,
+  field: Field,
+  label: string,
+  row: number,
+  visit: BlobInputVisitor,
+): unknown {
+  if (isBlobField(field)) {
+    return visit(value, label, row);
+  }
+  if (field.type instanceof Struct && isObject(value)) {
+    return mapBlobFields(value, field.type.children, `${label}.`, row, visit);
+  }
+  if (isList(field.type) && Array.isArray(value)) {
+    const child = field.type.children[0];
+    let out: unknown[] | undefined;
+    for (const [index, element] of value.entries()) {
+      const mapped = mapBlobField(
+        element,
+        child,
+        `${label}[${index}]`,
+        row,
+        visit,
+      );
+      if (mapped !== element) {
+        out ??= [...value];
+        out[index] = mapped;
+      }
+    }
+    return out ?? value;
+  }
+  return value;
+}
+
+/**
+ * Reads `Blob` / `File` values in the blob columns of `schema` into bytes so
+ * the synchronous conversion in {@link makeArrowTable} can accept them.
+ * Returns `data` itself when there is nothing to read.
+ */
+export async function resolveBlobInputs(
+  data: Array<Record<string, unknown>>,
+  schema?: SchemaLike,
+): Promise<Array<Record<string, unknown>>> {
+  if (schema === undefined || schema === null) {
+    return data;
+  }
+  const sanitized = sanitizeSchema(schema);
+  // Keyed by the Blob itself, so rows sharing one Blob (bare or as
+  // `{ data }`) read it once and share the bytes.
+  const reads = new Map<Blob, Promise<Uint8Array>>();
+  mapBlobInputs(data, sanitized, (value) => {
+    const source = blobToRead(value);
+    if (source !== undefined && !reads.has(source)) {
+      reads.set(
+        source,
+        source.arrayBuffer().then((buffer) => new Uint8Array(buffer)),
+      );
+    }
+    return value;
+  });
+  if (reads.size === 0) {
+    return data;
+  }
+  const bytes = new Map(
+    await Promise.all(
+      [...reads].map(async ([source, read]) => [source, await read] as const),
+    ),
+  );
+  return mapBlobInputs(data, sanitized, (value) => {
+    const source = blobToRead(value);
+    return source === undefined
+      ? value
+      : withBlobBytes(value, bytes.get(source) as Uint8Array);
+  });
+}
+
 function isObject(value: unknown): value is Record<string, unknown> {
   return (
     typeof value === "object" &&
@@ -1013,6 +1163,11 @@ export async function convertToTable(
     );
   }
 
+  processedData = await resolveBlobInputs(
+    processedData,
+    makeTableOptions?.schema,
+  );
+
   const table = makeArrowTable(processedData, makeTableOptions);
   return await applyEmbeddings(table, embeddings, makeTableOptions?.schema);
 }
@@ -1369,7 +1524,7 @@ export function ensureNestedFieldsExist(
     for (const field of schema.fields) {
       if (field.name in row) {
         if (
-          field.type.constructor.name === "Struct" &&
+          isPlainStructField(field) &&
           row[field.name] !== null &&
           row[field.name] !== undefined
         ) {
@@ -1386,10 +1541,9 @@ export function ensureNestedFieldsExist(
       } else {
         // Keep a missing struct valid while filling each of its children with
         // null. This is distinct from an explicitly null struct value.
-        completeRow[field.name] =
+        completeRow[field.name] = isPlainStructField(field)
-          field.type.constructor.name === "Struct"
+          ? ensureStructFieldsExist({}, field.type as Struct)
-            ? ensureStructFieldsExist({}, field.type as Struct)
+          : null;
-            : null;
       }
     }
 
@@ -1397,6 +1551,15 @@ export function ensureNestedFieldsExist(
   });
 }
 
+/**
+ * Blob fields are Arrow structs, but their values are bytes, URIs, or
+ * `{ data } | { uri }` inputs that the blob coercion in `makeArrowTable`
+ * handles, so they must not be filled in like ordinary structs.
+ */
+function isPlainStructField(field: Field): boolean {
+  return field.type.constructor.name === "Struct" && !isBlobField(field);
+}
+
 /**
  * Recursively ensures that all fields in a struct type exist in the data,
  * filling missing fields with null values.
@@ -1410,7 +1573,7 @@ function ensureStructFieldsExist(
   for (const childField of structType.children) {
     if (childField.name in data) {
       if (
-        childField.type.constructor.name === "Struct" &&
+        isPlainStructField(childField) &&
         data[childField.name] !== null &&
         data[childField.name] !== undefined
       ) {
@@ -1426,10 +1589,9 @@ function ensureStructFieldsExist(
     } else {
       // Keep a missing struct valid while filling each of its children with
       // null. This is distinct from an explicitly null struct value.
-      completeStruct[childField.name] =
+      completeStruct[childField.name] = isPlainStructField(childField)
-        childField.type.constructor.name === "Struct"
+        ? ensureStructFieldsExist({}, childField.type as Struct)
-          ? ensureStructFieldsExist({}, childField.type as Struct)
+        : null;
-          : null;
     }
   }
 

nodejs/lancedb/blob.ts

@@ -12,7 +12,46 @@ const DEDICATED_SIZE_THRESHOLD_KEY =
 const PACK_FILE_SIZE_THRESHOLD_KEY =
   "lance-encoding:blob-pack-file-size-threshold";
 
-export type BlobInput = {
+/**
+ * Bytes accepted for a blob value. `ArrayBuffer` is wrapped without copying.
+ * `Blob` and `File` are read with `arrayBuffer()`, which only the async write
+ * paths ({@link Connection.createTable}, {@link Table.add},
+ * {@link Table.mergeInsert}) can do.
+ */
+export type BlobData = Buffer | Uint8Array | ArrayBuffer | Blob;
+
+/** A URI accepted for a blob value. A `URL` is stored as its `href`. */
+export type BlobUri = string | URL;
+
+/**
+ * A value accepted for a `lance.blob.v2` column (see {@link blob}).
+ *
+ * Either inline bytes, a URI pointing at external bytes, or a struct that sets
+ * exactly one of `data` or `uri`. `null` and `undefined` write a null blob.
+ *
+ * @example
+ * ```ts
+ * import { pathToFileURL } from "node:url";
+ * import type { BlobInput } from "@lancedb/lancedb";
+ *
+ * const rows: { id: bigint; image: BlobInput }[] = [
+ *   { id: 1n, image: await (await fetch(url)).arrayBuffer() },
+ *   { id: 2n, image: pathToFileURL("/data/cat.png") },
+ *   { id: 3n, image: { data: new Blob(["hello"]) } },
+ * ];
+ * await table.add(rows);
+ * ```
+ */
+export type BlobInput =
+  | BlobData
+  | BlobUri
+  | { data: BlobData; uri?: null }
+  | { data?: null; uri: BlobUri }
+  | null
+  | undefined;
+
+/** A blob value normalized to the columns of the blob struct. */
+export type BlobValue = {
   data: Buffer | Uint8Array | null;
   uri: string | null;
 };
@@ -248,7 +287,77 @@ export type BlobRange = {
   end: bigint;
 };
 
-export function coerceBlobValue(value: unknown): BlobInput | null {
+/**
+ * Rewrites the synchronous-only widenings of {@link BlobInput} (`ArrayBuffer`,
+ * `URL`) into `Uint8Array` and URI strings, keeping the value's shape. Other
+ * values are returned unchanged and validated later by {@link coerceBlobValue}.
+ *
+ * Throws on `Blob` / `File`, which must be read into bytes first.
+ */
+export function normalizeBlobInput(value: unknown): unknown {
+  if (blobToRead(value) !== undefined) {
+    throw new Error(
+      "Blob and File values must be read asynchronously. Pass them to " +
+        "createTable, add, or mergeInsert, or convert them with " +
+        "`new Uint8Array(await value.arrayBuffer())`",
+    );
+  }
+  if (value instanceof ArrayBuffer) {
+    return new Uint8Array(value);
+  }
+  if (value instanceof URL) {
+    return value.href;
+  }
+  if (isBlobStruct(value)) {
+    // Read `data` and `uri` explicitly: spreading a class instance would drop
+    // fields defined as getters on its prototype.
+    const out: Record<string, unknown> = {
+      ...value,
+      data: value.data,
+      uri: value.uri,
+    };
+    let changed = false;
+    if (value.data instanceof ArrayBuffer) {
+      out.data = new Uint8Array(value.data);
+      changed = true;
+    }
+    if (value.uri instanceof URL) {
+      out.uri = value.uri.href;
+      changed = true;
+    }
+    return changed ? out : value;
+  }
+  return value;
+}
+
+/**
+ * Returns the `Blob` / `File` a blob value needs read, either the value itself
+ * or its `data` field, or `undefined` when there is nothing to read.
+ */
+export function blobToRead(value: unknown): Blob | undefined {
+  if (isBlobLike(value)) {
+    return value;
+  }
+  if (isBlobStruct(value) && isBlobLike(value.data)) {
+    return value.data;
+  }
+  return undefined;
+}
+
+/**
+ * Replaces the `Blob` that {@link blobToRead} found in `value` with `bytes`,
+ * keeping the value's shape.
+ */
+export function withBlobBytes(value: unknown, bytes: Uint8Array): unknown {
+  if (isBlobLike(value)) {
+    return bytes;
+  }
+  const record = value as Record<string, unknown>;
+  return { ...record, uri: record.uri, data: bytes };
+}
+
+export function coerceBlobValue(input: unknown): BlobValue | null {
+  const value = normalizeBlobInput(input);
   if (value == null) {
     return null;
   }
@@ -256,7 +365,9 @@ export function coerceBlobValue(value: unknown): BlobInput | null {
     return { data: value, uri: null };
   }
   if (ArrayBuffer.isView(value)) {
-    throw new Error("Blob data must be Buffer or Uint8Array");
+    throw new Error(
+      "Blob data must be Buffer, Uint8Array, ArrayBuffer, or Blob",
+    );
   }
   if (typeof value === "string") {
     if (value === "") {
@@ -264,23 +375,37 @@ export function coerceBlobValue(value: unknown): BlobInput | null {
     }
     return { data: null, uri: value };
   }
-  if (typeof value === "object") {
+  if (isBlobStruct(value)) {
-    const record = value as Record<string, unknown>;
+    const record = value;
     if (!("data" in record) && !("uri" in record)) {
       throw new Error(
         "Blob struct values must include a 'data' or 'uri' field",
       );
     }
+    const unknownKeys = Object.keys(record).filter(
+      (key) => key !== "data" && key !== "uri",
+    );
+    if (unknownKeys.length > 0) {
+      throw new Error(
+        `Blob struct values only support 'data' and 'uri', got ${unknownKeys
+          .map((key) => `'${key}'`)
+          .join(", ")}`,
+      );
+    }
     const uri = record.uri;
     if (uri === "") {
       throw new Error("Blob uri cannot be empty");
     }
     if (uri != null && typeof uri !== "string") {
-      throw new Error(`Blob uri must be a string or null, got ${typeof uri}`);
+      throw new Error(
+        `Blob uri must be a string, URL, or null, got ${typeof uri}`,
+      );
     }
     const data = record.data;
     if (data != null && !isBlobBytes(data)) {
-      throw new Error("Blob data must be Buffer, Uint8Array, or null");
+      throw new Error(
+        "Blob data must be Buffer, Uint8Array, ArrayBuffer, Blob, or null",
+      );
     }
     const bytes = (data as Buffer | Uint8Array | null | undefined) ?? null;
     const uriValue = uri ?? null;
@@ -292,7 +417,39 @@ export function coerceBlobValue(value: unknown): BlobInput | null {
     return { data: bytes, uri: uriValue };
   }
   throw new Error(
-    "Blob column values must be Buffer, Uint8Array, a URI string, null, or { data?, uri? }",
+    "Blob column values must be Buffer, Uint8Array, ArrayBuffer, Blob, a URI string or URL, null, or { data?, uri? }",
+  );
+}
+
+function isBlobLike(value: unknown): value is Blob {
+  return typeof Blob !== "undefined" && value instanceof Blob;
+}
+
+/**
+ * Whether `value` is a `{ data?, uri? }` struct: any plain object, or any
+ * other object with a `data` or `uri` field (such as a class instance), apart
+ * from the binary, `Blob`, and `URL` values that are blob inputs themselves.
+ */
+function isBlobStruct(value: unknown): value is Record<string, unknown> {
+  if (
+    typeof value !== "object" ||
+    value === null ||
+    Array.isArray(value) ||
+    ArrayBuffer.isView(value) ||
+    value instanceof ArrayBuffer ||
+    (typeof SharedArrayBuffer !== "undefined" &&
+      value instanceof SharedArrayBuffer) ||
+    isBlobLike(value) ||
+    value instanceof URL
+  ) {
+    return false;
+  }
+  const prototype = Object.getPrototypeOf(value);
+  return (
+    prototype === Object.prototype ||
+    prototype === null ||
+    "data" in value ||
+    "uri" in value
   );
 }
 

nodejs/lancedb/connection.ts

@@ -8,6 +8,7 @@ import {
   fromTableToStreamBuffer,
   isArrowTable,
   makeArrowTable,
+  resolveBlobInputs,
 } from "./arrow";
 import {
   Table as ArrowTable,
@@ -1133,7 +1134,11 @@ async function parseTableData(
   if (isArrowTable(data)) {
     table = sanitizeTable(data);
   } else {
-    table = makeArrowTable(data as Record<string, unknown>[], options);
+    const records = await resolveBlobInputs(
+      data as Record<string, unknown>[],
+      options?.schema,
+    );
+    table = makeArrowTable(records, options);
   }
   if (streaming) {
     const buf = await fromTableToStreamBuffer(

nodejs/lancedb/index.ts

@@ -84,7 +84,14 @@ export {
 } from "./arrow";
 
 export { blob, isBlobField, BlobFile } from "./blob";
-export type { BlobOptions, BlobRange, BlobReadOptions } from "./blob";
+export type {
+  BlobData,
+  BlobInput,
+  BlobOptions,
+  BlobRange,
+  BlobReadOptions,
+  BlobUri,
+} from "./blob";
 
 export {
   Connection,

nodejs/lancedb/schema.ts

@@ -69,12 +69,18 @@ class SchemaInferrer {
       this.addField(path, value, row);
     } else if (this.providedSchema === undefined) {
       this.updateInferredField(path, value, row, current);
+    } else if (current instanceof DeferredTypeEvidence) {
+      if (value != null) {
+        this.addSchemaField(this.providedSchema, path, value, row);
+      }
+    } else if (current instanceof FieldTree || DataType.isStruct(current)) {
+      assertStructValue(path, value, row);
     }
   }
 
   private addField(path: string[], value: unknown, row: number): void {
     if (this.providedSchema !== undefined) {
-      this.addSchemaField(this.providedSchema, path, row);
+      this.addSchemaField(this.providedSchema, path, value, row);
       return;
     }
 
@@ -95,15 +101,31 @@ class SchemaInferrer {
     }
   }
 
-  private addSchemaField(schema: Schema, path: string[], row: number): void {
+  private addSchemaField(
+    schema: Schema,
+    path: string[],
+    value: unknown,
+    row: number,
+  ): void {
     const field = fieldAtPath(schema, path);
     if (field === undefined) {
       throw new Error(
         `Found field not in schema: ${path.join(".")} at row ${row}`,
       );
     }
+    if (DataType.isStruct(field.type)) {
+      assertStructValue(path, value, row);
+    }
 
-    const conflict = this.fields.set(path, field.type);
+    // Nulls are kept as deferred evidence so that a struct field seen first as
+    // null can be replaced by a record in a later row, just as a record seen
+    // first already ignores later nulls.
+    const conflict = this.fields.set(
+      path,
+      DeferredTypeEvidence.from(value, row) ?? field.type,
+      (existing) =>
+        existing instanceof DeferredTypeEvidence && existing.isOnlyNulls(),
+    );
     if (conflict !== undefined) {
       throw branchConflictError(conflict, row, "Struct");
     }
@@ -483,6 +505,26 @@ function assertSupportedValue(
   }
 }
 
+/**
+ * Rejects primitives, arrays, and typed arrays given for a struct field, which
+ * would otherwise be written as a struct with every child null.
+ */
+function assertStructValue(path: string[], value: unknown, row: number): void {
+  if (
+    value == null ||
+    (typeof value === "object" &&
+      !Array.isArray(value) &&
+      !ArrayBuffer.isView(value))
+  ) {
+    return;
+  }
+  const kind =
+    typeof value === "object" ? value.constructor.name : typeof value;
+  throw new Error(
+    `Expected a struct value for field ${path.join(".")} at row ${row}, got ${kind}.`,
+  );
+}
+
 function fieldAtPath(schema: Schema, path: string[]): Field | undefined {
   let fields = schema.fields;
   let field: Field | undefined;