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7.3.0 • Public • Published


Lowest Common Denominator API to supported Databases

npm code style: prettier loc

Defines 3 things:

  • CommonDB interface
  • CommonDao class
  • DBQuery class

CommonDB serves as a Lowest Commond Denominator between different DB implementations (see further). So you can use same syntax, e.g getById<DBM>(id: string): Promise<DBM | undefined> across different DBs.

DBQuery allows to use the same query syntax across different DBs! E.g:

const q = DBQuery.create('table1')
  .filterEq('type', 'cat')
  .filter('updated', '>', '2019-01-17')
  .order('name', true)
await db.runQuery(q)

So, you can run it against Datastore, Firestore, Redis, MongoDB, Airtable, etc. Different DBs, same syntax!

You can swap DB implementations without changing your application code. Migrate Datastore to Firestore? Easy.

You can test your code against InMemoryDB (that implements full CommonDB interface, even with querying, streaming, etc). So, your unit tests can use exactly same querying syntax, or even exactly same services, DAOs. Just swap real DB with InMemoryDB in your setupJest.ts (for example).

Supported databases


  • CommonDB, CommonDao, DBQuery
  • Streaming (Node.js streams with backpressure)
  • DBM / BM, validation, conversion (Joi-powered)
  • Conventions
    • String ids
    • created, updated (unix timestamps)
    • Dates as ISO strings, e.g 2019-06-21
    • Timestamps as unixtimestamps (seconds, not milliseconds; UTC)
    • Complex objects as JSON serialized to string (DBM), converted to object (BM)


CommonDB is a low-level API (no high-level sugar-syntax). CommonDao is the opposite - a high-level API (with convenience methods), built on top of CommonDB.

Concerns of CommonDB:

  • Access to DB (all tables): CRUD (create, read, update, delete)
  • Batch methods (cause they can be more optimal if implemented "natively")
  • Querying
  • Streaming

Concerns of CommonDao:

  • Access to one DB Table ("kind")
  • Transformation between DBM and BM, validation/conversion
  • Auto-generating id, created, updated fields
  • Anonymization hook to be able to plug your implementation (privacy by design)

CommonDB API


ping(): Promise<void>

Call this to check that DB connection, credentials, configuration is working. Should throw an error if any of above is invalid.


getByIds<DBM>(table: string, ids: string[]): Promise<DBM[]>

await db.getByIds('table1', ['id1, 'id2'])
// [ { id: 'id1', ... }, { id: 'id2', ... } ]

Should return items in the same order as ids in the input.

Only returns items that are found, does not return undefined (absent) items.


runQuery<DBM>(q: DBQuery<DBM>): Promise<RunQueryResult<DBM>>

const q = DBQuery.create('table1').filterEq('type', 'cat').order('name', true) // desc
await db.runQuery(q)
// { records: [ { ... }, { ... }, ... ] }

runQueryCount(q: DBQuery): Promise<number>

await db.runQuery(DBQuery.create('table1'))
// 5

streamQuery<DBM>(q: DBQuery<DBM>): ReadableTyped<DBM>

Returns ReadableTyped (typed wrapper of Node.js Readable).

Streams in Node.js support back-pressure by default (if piped properly by the consumer).

const q = DBQuery.create('table1') // "return all items" query
await _pipeline([
  writableForEach(item => {
// { item1 }
// { item2 }
// ...

saveBatch<DBM>(table: string, dbms: DBM[]): Promise<void>

Since CommonDB is a "minimal API", there's no save method for a single item, only for multiple. Pass an array with single item to save just one item.

const items = [
  { item1 },
  { item2 },
await db.saveBatch('table1', items) // returns void
await db.runQuery(DBQuery.create('table1') // "get all" query
// [ { item1 }, { item2 } ]

deleteByIds(table: string, ids: string[]): Promise<number>

Returns number of deleted items (not all CommonDB implementations support that).

await db.deleteByIds('table1', ['id1', 'id2'])
// 2

deleteByQuery(q: DBQuery): Promise<number>

Returns number of deleted items.

await db.deleteByQuery(DBQuery.create('table1'))
// 2

getTables(): Promise<string[]>

await db.getTables()
// [ 'table1', 'table2' ]

getTableSchema(table: string): Promise<CommonSchema>

await db.getTableSchema('table1')
// todo: describe CommonSchema example

createTable(schema: CommonSchema): Promise<void>

Applicable to Relational DBs, like MySQL. Will invoke smth like create table Table1 ... ;. Takes a CommonSchema as an argument.


Object that defines "DB Query".

// Simplest query - "get all" query
// where type = "cat"
DBQuery.create('table1').filter('type', '=', 'cat')
// OR
DBQuery.create('table1').filterEq('type', 'cat')
// Where updated > 2019-01-17
DBQuery.create('table1').filter('updated', '>', '2019-01-17')
// order by 'name'
DBQuery.create('table1').filter('updated', '>', '2019-01-17').order('name')
// order by 'name' in descending order
DBQuery.create('table1').filter('updated', '>', '2019-01-17').order('name', true)


.filter(key: string, operator: Operator, value: any)
.filter('updatedDate', '>', '2019-01-17')
.filterEq(key: string, value: any)
.filterEq('updated', true)
.order(key: string, descending: boolean = false)
.order('updated') // asc
.order('updated', true) // desc
.limit(lim: number)
.limit(0) // no limit
.select(fields: string[])

Allows "projection queries" - queries that return subset of fields. Like select a,b,c from Table in SQL, as opposed to select * from Table.

Passing empty array will actually return an array of empty objects (documented edge case).

.select([]) // returns [ {}, {}, {} ]
.select(['id']) //=> [ { id: 'id1' }, { id: 'id2' }, ... ]

DEBUG namespaces

  • nc:db-lib:commondao
  • nc:db-lib:inmemorydb


  • / root
  • /adapter/file
  • /adapter/cachedb
  • /testing
    • dbTest
    • daoTest
    • Test models, utils, etc
  • /validation
    • Joi validation schemas for DBQuery, CommonDBOptions, CommonSchema, etc


  • engines.node >= LTS
  • main: dist/index.js: commonjs, es2019
  • types: dist/index.d.ts: typescript types
  • /src folder with source *.ts files included


npm i @naturalcycles/db-lib

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