[WIP] Trigger Based Table Diff Tracking

[stevensJourney]

Overview

We currently expose watched query functionality which allows watching changes of SQLite query's result set. This PR adds methods which can be used to track and process changes to individual SQLite tables.

Temporary SQLite triggers and tables are used to populate a set of table change operations. Records for table row INSERT, UPDATEandDELETE` operations are created as changes occur.

This PR currently adds 2 new SQLite trigger based methods.

Creating a Diff Trigger

createDiffTrigger Configures temporary SQLite triggers which populate a temporary SQLite table with operations as they occur.

const dispose = await database.triggers.createDiffTrigger({
  source: 'ps_data__lists',
  destination: tempTable,
  columns: ['name'],
  operations: [DiffTriggerOperation.INSERT, DiffTriggerOperation.UPDATE]
});

Processing Change Operations

A more convenient trackTableDiff method uses createDiffTrigger to get table changes, but adds additional logic to consume the changes as they occur.

The example below uses triggers to process todo records as they are inserted/created.

database.triggers.trackTableDiff({
  source: 'ps_data__todos',
  columns: ['list_id'],
  filter: `json_extract(NEW.data, '$.list_id') = '${firstList.id}'`,
  operations: [DiffTriggerOperation.INSERT],
  onChange: async (context) => {
    // Fetches the todo records that were inserted during this diff
    const newTodos = await context.getAll<Database['todos']>(/* sql */ `
      SELECT
        todos.*
      FROM
        DIFF
        JOIN todos ON DIFF.id = todos.id
    `);

    // Process newly added TODOs
  }
});

Docs

For more info see the unit tests and API doc comments.

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