Magento 2 Declarative Schema

© 2019 Magento, Inc. Page | 1
Magento 2.3
Declarative Schema

© 2019 Magento, Inc.
.
Page | 2
Lead Developer at BORN Group
Atish Goswami

Agenda

Agenda
• What is Declarative Schema ?
• Declaring table schemes
• Updating existing table schemes
• New CLI commands and arguments
• Schema Rollback

Not In Scope

Not in Scope
• Applying Data Patches
• Patch Rollbacks
• Schema Patches (Trigger/Stored Procedures)

What is Declarative
Schema ?

Declarative Schema
• Newer way of handling Setup Script Operations
• Setup Scripts are still supported in 2.3.x versions (EOL unknown)
• Might be Backported to 2.2.x newer versions
• Declarative Schema and Setup Scripts don’t work together
• If developing backwards compatible modules use Setup Script

Why Declarative Schema ?

Issues with Setup Scripts
• Setup Scripts get complicated to manage overtime
• Module sequencing needs to be handled properly
• Confusing to manage Install vs Upgrade scripts
• Version number mishap happens
• No Rollbacks

Will Declarative Schema
help ?

Declarative Schema Offers
• Avoidance of missed/repeated SQL operations
• Installation testing using dry-run mode
• Performance optimization
• Support for rollbacks *

Getting Started

<module_root>/registration.php

<module_root>/etc/module.xml
Note : Declarative Schema does not require version number

<module_root>/etc/db_schema.xml
New xml file introduced by Declarative Schema

Declaring a table

<table/> Attributes
• name
– Name of the table
– Required
• resource (default)
– Database connection to use for the operation
– Allowed values – default, sales, checkout
• engine (innodb)
– MySQL Table engine
– Allowed values – innodb, memory

<table/> Attributes (Contd)
• comment (not comments added)
– Comment Relating the table
• charset (utf8)
– Charset for the table
• collation (utf8_general_ci)
– Collation to match the charset
• onCreate (empty)
– Helps trigger a task after the table is created

Declaring integer columns

<module_root>/etc/db_schema.xml

<column/> Integer Attributes
• name
– Name of the column
– Required
• xsi:type
– Allowed Values – (tinyint, int, smallint, bigint, boolean)
– Required
• default (NULL)
– Provide default column value
– Can provide only value as integer
• padding (tinyint[2], int[11], smallint[5], bigint[20], boolean[1])
– Padding values for the integer type columns
– Allowed Values (2 - 1024)

<column/> Integer Attributes
• unsigned (false)
– If column contains negative values need to be true
• identity (false)
– If true column will be auto increment
– The column need to be declared in primary index as well
• nullable (true)
– If column will have NULL values
• comment (no comments are added)
– Comment for the column
– Helps trigger a task after the column is created

Declaring text columns

<column/> Text Attributes
• name
– Name of the Column
– Required
• xsi:type
– Allowed Values – (varchar, text, mediumtext, longtext)
– Required
• default
– Can provided only for varchar
• length
– Length of the field
– varchar allowed max length is 1024
– text mediumtext longtext length can’t be defined

• nullable (true)

Declaring binary columns

• xsi:type
– Allowed Values – (varbinary, blob, mediumblob, longblob)
– Required
• default
– Can provided only for varbinary
• length
– Length of the field
– varbinary allowed max length is 255
– blob mediumblob longblob length can’t be defined

• nullable (true)

Declaring decimal
columns

• xsi:type
– Allowed Values – (decimal, float, double)
– Required
• default
• precision
– Total digits of the decimal numbers
• scale
– Total digits after the decimal point

• nullable (true)
• unsigned (false)
– If column contains negative values need to be true

Declaring a time column

• name
– Name of the column
– Required
• xsi:type
– Allowed Values – (timestamp, datetime, date)
– Required
• default
– Allowed Values – (CURRENT_TIMESTAMP, 0, NULL)
• on_update (false)
– MySQL on update will be implemented

• nullable (true)

Declaring a primary key

Declaring a foreign key

Declaring a unique key

Declaring an index

<index/> Attributes
• indexType
– fulltext
– hash
– btree

Generating
db_schema_whitelist.json

<module_root>/etc/db_schema_whitelist.json

Testing with dry-run

var/log/dry-run-installation.log

Applying Database
Schema

Modifying the table
column

Testing with safe-mode

Destructive Operations
• Deleting a table
• Deleting a column
• Reducing column length
• Changing column precision
• Changing column type

var/declarative_dumps_csv/
{column_name_column_type_other_dimensions}.csv
var/declarative_dumps_csv/{table_name}.csv

Restoring Schema Data

Uninstalling a Module

Converting Setup Script
to Declarative Schema

Limitations
• Custom DDL operations are ignored. It supports only DDL operations that are
present in MagentoFrameworkDBAdapterPdoMysql
• Raw SQL in InstallSchema or UpgradeSchema scripts are ignored.
• DDL statements in the Recurring file won’t be transferred to the new schema
because the file needs to run during each installation or upgrade.

Questions ?

Thank You

Magento 2 Declarative Schema

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