androidx SQLite Web Worker

This web worker provides an interface to the SQLite WASM API, allowing the main thread to perform database operations off the main thread.

Messaging Protocol

The communication between the driver (main thread) and the worker is done via messages. All messages, both requests and responses, are wrapped in an object with an id field that is used to correlate requests with responses.

Request Messages

A request from the driver to the worker has the following structure:

{
  "id": <number>,
  "data": {
    "cmd": "<command_name>",
    ...
  }
}

• id: A unique identifier for the request.
• data: An object containing the command and its parameters.
  • cmd: The name of the command to execute.

Response Messages

A response from the worker to the driver has the following structure:

Success:

{
  "id": <number>,
  "data": { ... }
}

Error:

{
  "id": <number>,
  "error": "<error_message>"
}

• id: The identifier of the request this response corresponds to.
• data: An object containing the result of a successful command.
• error: A string message describing the error if the command failed.

Commands

open

Opens a new database connection. If successful responds with the database connection unique ID.

Request:

{
  "cmd": "open",
  "fileName": "<string>"
}

Success Response:

{
  "databaseId": <number>
}

prepare

Prepares a new SQL statement for execution. If successful responds with the statement unique ID and information about the prepared statement.

Request:

{
  "cmd": "prepare",
  "databaseId": <number>,
  "sql": "<string>"
}

Success Response:

{
  "statementId": <number>,
  "parameterCount": <number>,
  "columnNames": ["<string>", ...]
}

step

Executes a prepared statement. Involves binding parameters sent in the request and then stepping through all the result rows of the statement to respond with their column result.

Request:

{
  "cmd": "step",
  "statementId": <number>,
  "bindings": [...]
}

Success Response:

{
  "rows": [[...], ...],
  "columnTypes": [<number>, ...]
}

close

Closes a prepared statement or a database connection. This is a one-way command; no success response is sent.

Request:

{
  "cmd": "close",
  "statementId": <number>,
  "databaseId": <number>
}