Data Ingestion

DuckDB-Wasm has multiple ways to import data, depending on the format of the data.

There are two steps to import data into DuckDB.

First, the data file is imported into a local file system using register functions (registerEmptyFileBuffer, registerFileBuffer, registerFileHandle, registerFileText, registerFileURL).

Then, the data file is imported into DuckDB using insert functions (insertArrowFromIPCStream, insertArrowTable, insertCSVFromPath, insertJSONFromPath) or directly using FROM SQL query (using extensions like Parquet or Wasm-flavored httpfs).

Insert statements can also be used to import data.

Data Import

Open & Close Connection

// Create a new connection
const c = await db.connect();

// ... import data

// Close the connection to release memory
await c.close();

Apache Arrow

// Data can be inserted from an existing arrow.Table
// More Example https://arrow.apache.org/docs/js/
import { tableFromArrays } from 'apache-arrow';

// EOS signal according to Arrow IPC streaming format
// See https://arrow.apache.org/docs/format/Columnar.html#ipc-streaming-format
const EOS = new Uint8Array([255, 255, 255, 255, 0, 0, 0, 0]);

const arrowTable = tableFromArrays({
  id: [1, 2, 3],
  name: ['John', 'Jane', 'Jack'],
  age: [20, 21, 22],
});

await c.insertArrowTable(arrowTable, { name: 'arrow_table' });
// Write EOS
await c.insertArrowTable(EOS, { name: 'arrow_table' });

// ..., from a raw Arrow IPC stream
const streamResponse = await fetch(`someapi`);
const streamReader = streamResponse.body.getReader();
const streamInserts = [];
while (true) {
    const { value, done } = await streamReader.read();
    if (done) break;
    streamInserts.push(c.insertArrowFromIPCStream(value, { name: 'streamed' }));
}

// Write EOS
streamInserts.push(c.insertArrowFromIPCStream(EOS, { name: 'streamed' }));

await Promise.all(streamInserts);

CSV

// ..., from CSV files
// (interchangeable: registerFile{Text,Buffer,URL,Handle})
const csvContent = '1|foo\n2|bar\n';
await db.registerFileText(`data.csv`, csvContent);
// ... with typed insert options
await c.insertCSVFromPath('data.csv', {
    schema: 'main',
    name: 'foo',
    detect: false,
    header: false,
    delimiter: '|',
    columns: {
        col1: new arrow.Int32(),
        col2: new arrow.Utf8(),
    },
});

JSON

// ..., from JSON documents in row-major format
const jsonRowContent = [
    { "col1": 1, "col2": "foo" },
    { "col1": 2, "col2": "bar" },
];
await db.registerFileText(
    'rows.json',
    JSON.stringify(jsonRowContent),
);
await c.insertJSONFromPath('rows.json', { name: 'rows' });

// ... or column-major format
const jsonColContent = {
    "col1": [1, 2],
    "col2": ["foo", "bar"]
};
await db.registerFileText(
    'columns.json',
    JSON.stringify(jsonColContent),
);
await c.insertJSONFromPath('columns.json', { name: 'columns' });

// From API
const streamResponse = await fetch(`someapi/content.json`);
await db.registerFileBuffer('file.json', new Uint8Array(await streamResponse.arrayBuffer()))
await c.insertJSONFromPath('file.json', { name: 'JSONContent' });

Parquet

// from Parquet files
// ...Local
const pickedFile: File = letUserPickFile();
await db.registerFileHandle('local.parquet', pickedFile, DuckDBDataProtocol.BROWSER_FILEREADER, true);
// ...Remote
await db.registerFileURL('remote.parquet', 'https://origin/remote.parquet', DuckDBDataProtocol.HTTP, false);
// ... Using Fetch
const res = await fetch('https://origin/remote.parquet');
await db.registerFileBuffer('buffer.parquet', new Uint8Array(await res.arrayBuffer()));

// ..., by specifying URLs in the SQL text
await c.query(`
    CREATE TABLE direct AS
        SELECT * FROM 'https://origin/remote.parquet'
`);
// ..., or by executing raw insert statements
await c.query(`
    INSERT INTO existing_table
    VALUES (1, 'foo'), (2, 'bar')`);

httpfs (Wasm-Flavored)

// ..., by specifying URLs in the SQL text
await c.query(`
    CREATE TABLE direct AS
        SELECT * FROM 'https://origin/remote.parquet'
`);

Tip If you encounter a Network Error (Failed to execute 'send' on 'XMLHttpRequest') when you try to query files from S3, configure the S3 permission CORS header. For example:

[
    {
        "AllowedHeaders": [
            "*"
        ],
        "AllowedMethods": [
            "GET",
            "HEAD"
        ],
        "AllowedOrigins": [
            "*"
        ],
        "ExposeHeaders": [],
        "MaxAgeSeconds": 3000
    }
]

Insert Statement

// ..., or by executing raw insert statements
await c.query(`
    INSERT INTO existing_table
    VALUES (1, 'foo'), (2, 'bar')`);