The discussion between knex.js and postgreSQL

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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