lancedb/docs/src/js/functions/blob.md

@lancedb/lancedb • Docs

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@lancedb/lancedb / blob

Function: blob()

function blob(name, options): Field

Declares a lance.blob.v2 column.

Query results are descriptors, not payload bytes. Use Table.fetchBlobs or Table.fetchBlobFiles to read bytes. Blobs inside lists can be written and queried as descriptors, but cannot currently be fetched because a row ID does not identify a list element.

Parameters

• name: string

• options: BlobOptions = {}

Returns

Field

Example

import { readFile } from "node:fs/promises";
import { Field, Int64, Schema } from "apache-arrow";
import { blob, connect } from "@lancedb/lancedb";

const db = await connect("./data");
const video = await readFile("clip.mp4");
const table = await db.createTable(
  "videos",
  [{ id: 1n, video }],
  {
    schema: new Schema([
      new Field("id", new Int64()),
      blob("video"),
    ]),
  },
);

const rows = await table.query().select(["id"]).withRowId().toArray();
const rowIds = rows.map((row) => row._rowid as bigint);
const bytes = await table.fetchBlobs("video", rowIds);

const [handle] = await table.fetchBlobFiles("video", rowIds);
const size = handle!.size();
const header = await handle!.readRange(0n, size < 65536n ? size : 65536n);