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sql.jsのデータベースファイルをブラウザからFileSystemAccessAPIを使ってローカルに保存、復元を行ったメモ

概要

SQLite in a PWA with FileSystemAccessAPIを参考に、File_System_Access_APIを使って、SQLITEの保存・復元を行ったメモ。
メモリ上にSQLiteが作成されるので、巨大なDBの管理には工夫が必要そう。
なお、File_System_Access_APIが動くブラウザは限られており、今回はchromeで動作確認している。

ソースコード

環境

  • chorome 103.0.5060.53
  • sql.js 1.7.0

ソースコード

  • sql.jsはWebAssemblyとしてSQLiteを読み込む必要がある。
src/domain/sqlite/initSQL.ts
import initSqlJs from 'sql.js'
export const initSQL = async (wasmFileDirPath: string) => {
  const SQL = await initSqlJs({
    locateFile: (file) => `${wasmFileDirPath}/${file}`,
  })

  return SQL
}
src/domain/sqlite/constants.ts
export const WASM_FILE_PATH =
  'https://cdnjs.cloudflare.com/ajax/libs/sql.js/1.7.0'
  • showDirectoryPickerでデータベースファイルの保存先を選んでいる。
src/domain/sqlite/OnMomorySQLite.ts
import { WASM_FILE_PATH } from './constants'
import { initSQL } from './initSQL'
import type { Database } from 'sql.js'

const EXPORT_FILE_NAME = 'my_data.db'
export class OnMemorySQLite {
  #dirHandle: FileSystemDirectoryHandle | null = null
  constructor(private db: Database) {}
  run(sql: string): void {
    this.db.run(sql)
  }
  exec(sql: string) {
    return this.db.exec(sql)
  }
  async export() {
    const binaryArray: Uint8Array = this.db.export()
    const dirHandle = await this.#getDirectoryPicker()
    if (!dirHandle) return

    try {
      const fileHandle = await dirHandle.getFileHandle(EXPORT_FILE_NAME, {
        create: true,
      })
      const writable = await fileHandle.createWritable()
      await writable.write(binaryArray)
      await writable.close()
    } catch (e) {
      // キャンセル時AbortError
      console.log(e)
    }
  }
  async load() {
    const dirHandle = await this.#getDirectoryPicker()
    if (!dirHandle) return
    const fileHandle = await dirHandle.getFileHandle(EXPORT_FILE_NAME)
    const file = await fileHandle.getFile()
    const arrayBuffer = await file.arrayBuffer()

    const dbAsUint8Array = new Uint8Array(arrayBuffer)
    const SQL = await initSQL(WASM_FILE_PATH)

    this.db = new SQL.Database(dbAsUint8Array)
  }

  async #getDirectoryPicker() {
    if (this.#dirHandle) return this.#dirHandle
    try {
      const dirHandle = await window.showDirectoryPicker()
      this.#dirHandle = dirHandle
      return dirHandle
    } catch (e: any) {
      console.log(e)
    }
  }
}

src/domain/sqlite/index.ts
import { WASM_FILE_PATH } from './constants'
import { initSQL } from './initSQL'
import { OnMemorySQLite } from './OnMemorySQLite'
import type { Database } from 'sql.js'

let client: OnMemorySQLite | null = null
export const getOnMemoryDB = async () => {
  if (client) return client
  const SQL = await initSQL(WASM_FILE_PATH)
  const db = new SQL.Database()
  client = new OnMemorySQLite(db)
  return client
}

  • 動作を確認するだけの単純なページ。
src/contents/Top.tsx
import React, { useEffect, useState } from 'react'
import styled from 'styled-components'
import { getOnMemoryDB } from '@/domain/sqlite'
import type { OnMemorySQLite } from '@/domain/sqlite/OnMemorySQLite'

const Wrapper = styled.div`
  position: relative;
  width: 100%;
  min-height: 100%;
  padding-bottom: 100px;
`

const Top: React.FC = () => {
  const [db, setDB] = useState<OnMemorySQLite | null>(null)
  const [ret, setRet] = useState('')
  useEffect(() => {
    ;(async () => {
      setDB(await getOnMemoryDB())
    })()
  }, [])
  return (
    <Wrapper>
      {!db ? (
        <></>
      ) : (
        <div>
          <button
            onClick={() => {
              db.run(` CREATE TABLE IF NOT EXISTS people (name TEXT, age INT);`)
              db.run(
                ` 
                INSERT INTO people VALUES ('Michel',3);
                INSERT INTO people VALUES ('JOHNSON',4);`,
              )
            }}
          >
            seed
          </button>
          <button
            onClick={() => {
              const result = db.exec(`SELECT * from people;`)
              setRet(JSON.stringify(result))
            }}
          >
            select
          </button>
          <button onClick={() => db.export()}>export</button>
          <button onClick={() => db.load()}>load</button>
          <div>{ret}</div>
        </div>
      )}
    </Wrapper>
  )
}
export default Top

参考

HTMLのファイルに関するAPIの最新の事情

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Help us understand the problem. What are the problem?