This document discusses using knex.js to solve schema change problems. Knex.js is a SQL query builder that can be used with Node.js and relational databases. It features query building, pooling, transactions, migrations, and seed files. Migrations allow defining schema changes, and seed files populate data. Testing, automatic deployment, and using only JavaScript helps avoid crashes during schema updates and reduces operation errors.

1. Len Chang
08.18 2019
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2. ▪ Me
▪ The introduction of knex.js
▪ What’s the problem that schema change ?
▪ Create seed data and migration files
▪ How to solve the problem ?
▪ Integrate it with Bitbucket pipeline
▪ Q & A
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3. ▪ Len Chang
▪ Engineer
▪ Like..
▪ Baseball / Beer / Finance
▪ Coding
▪ JavaScript / Typescript
▪ DB
▪ PostgreSQL / Elasticsearch
▪ Volunteer
▪ Nantou Code Geek
▪ You can find me..
▪ LinkedIn
▪ Facebook
▪ PPT Online
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4. Library Docs (Link)
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5. ▪ Knex.js is a "batteries included" SQL query builder
for Postgres, MSSQL, MySQL, MariaDB, SQLite3, Oracle, and Amazon
Redshift designed to be flexible, portable, and fun to use.
▪ Basically it’s the major choice when you use nodejs and RDBMS to do the backend
server.
▪ Features
▪ Query Builder
▪ Pooling
▪ Transactions
▪ Migrations
▪ Seed files
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6. ▪ Query Builder
▪ The heart of the library, the knex query builder is the interface used for building and
executing standard SQL queries, such as select, insert, update, delete.
▪ Example
knex({ a: 'table', b: 'table' })
.select({
aTitle: 'a.title',
bTitle: 'b.title'
})
.whereRaw('?? = ??', ['a.column_1', 'b.column_2’])
// select "a"."title" as "aTitle", "b"."title" as "bTitle" from "table" as "a", "table" as "b" where "a"."column_1" = "b"."column_2"
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7. Application
▪ Pooling
▪ The client created by the configuration initializes a connection pool, using the tarn.js
library. This connection pool has a default setting of a min: 2, max: 10
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Pooling
Action
Action
Action
PG
Application
Action
Action
Action
PG

8. ▪ Transactions
▪ All queries within a transaction are executed on the same database connection, and run
the entire set of queries as a single unit of work. Any failure will mean the database will
rollback any queries executed on that connection to the pre-transaction state.
▪ Methods
1. As a transaction object
2. As a query builder
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as a transaction object

9. ▪ Transactions
▪ Methods
1. As a transaction object
2. As a query builder
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as a transaction object

10. ▪ Migrations
▪ Migrations allow for you to define sets of schema changes so upgrading a database is a
breeze.
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11. ▪ Seed files
▪ Seed files allow you to populate your database with test or seed data independent of your
migration files.
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Run seed

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13. Testing
1. How to avoid crashing when you
update schema ?
▪ Testing
2. How to avoid operation error ?
▪ Deploy system automatically
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DB
(version + 1)
Script:
Updating schema
Success (Commit) Failed (Rollback)
DB
(version + 1)
DB
(version)
Dev DB
Script:
Updating schema
QA DB
PROD DB
Dev DB
Dev DB
QA DB
Script:
Updating schemaScript:
Updating schema

14. 3. Doesn’t need to use another tool or code language to do it.
▪ Just JavaScript
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15. ▪ Summary
▪ How to avoid crashing when you updated schema ?
▪ Testing
▪ How to avoid operation error ?
▪ Deploying system automatically
▪ Doesn’t need to use another tool or code language to do it
▪ Just JavaScript
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17. ▪ Migration
1. knex init => knexfile.ts
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18. ▪ Migration
2. knex migrate:make migration
▪ Up / Down Functions
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19. ▪ Migration
3. knex migrate:latest
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Check migration record
Run
unrecorded
files

20. ▪ Migration Process
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knexfile.ts
20190814170951_migration.ts
Success (Commit)Failed (Rollback)
Run Migration

21. ▪ Seed data
1. knex init => knexfile.ts
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22. ▪ Seed data
2. Create seed data
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23. ▪ Seed data
3. Create seed handling script
and Running
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24. ▪ Seed Process
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Seed data of tables
Seed handling Scripts
knex seed:run
DB

25. Testing, deploying system automatically and just javascript !
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26. ▪ Testing
▪ Embedded seed testing in migration
Process
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Transaction
Transaction

27. ▪ Testing
▪ Dividing Environment
▪ All migration script is knex migrate:latest, but
it run different script by different env.
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28. ▪ deploying system automatically
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29. ▪ Just javascript
▪ …well…. Just you said that….only javascript.
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32. ▪ Advantage
▪ Reduce operation error !
▪ Deploy schema simpler and safer.
▪ Do it by JS developer.
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33. LinkedIn
Facebook
PPT Online
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