varcharPreferred

Last updated: September 2, 2025

varcharMaxSize is a custom policy check that checks for numeric characters in VARCHAR columns.

This example works for Oracle. You can use this check as it is or customize it further to fit your needs in your SQL database.

Notes:

Only basic INSERT or UPDATE statements are supported Inserting multiple rows within same INSERT is not supported LoadData change types are not supported by checks

Before you begin

Scope	Database
database	Oracle

Liquibase Secure 4.29.0+
Configure a valid Liquibase Secure license key
Python 3.10.14+. See here for the official Python tutorial
Create a Check Settings file
Java Development Kit 17+ (available for Open JDK and Oracle JDK)
Linux, macOS, or Windows operating system
Ensure the Liquibase Checks extension is installed.
- In Liquibase 4.31.0+, it is already installed in the /liquibase/internal/lib directory, so no action is needed.
- If the checks JAR is not installed, download liquibase-checks-<version>.jar and put it in the liquibase/lib directory.
- (Maven users only) Add the liquibase-checks dependency to your pom.xml file. See Add extensions with Maven for more information.

Tip: Downloading Python itself is not required to create custom checks in the Liquibase checks framework, but it may be useful to test checks against Python 3.10.14+.

Procedure

These steps describe how to create the Custom Policy Check. It does not exist by default in Liquibase Secure.

Add this code to your Checks Settings file:

varcharMaxSize Python Script

# # #
# # # This script ensures all VARCHAR columns are under a maximum size
# # #
# # # Notes:

    # # #
# # # Helpers come from Liquibase
# # #
import sys
import liquibase_utilities

# # #
# # # Retrieve log handler
# # # Ex.liquibase_logger.info(message)
# # #
liquibase_logger = liquibase_utilities.get_logger()

# # #
# # # Retrieve status handler
# # #
liquibase_status = liquibase_utilities.get_status()

# # #
# # # Retrive maximum size from check definition
# # #
max_size = int(liquibase_utilities.get_arg("VARCHAR_MAX"))

# # #
# # # Retrieve database object
# # #
database_object = liquibase_utilities.get_database_object()

# # #
# # # Skip
if not a varchar column
# # #
if "column" in database_object.getObjectTypeName().lower() and "varchar" in str(database_object.getType()).lower():
    column_name = database_object.getName()
column_size = int(database_object.getType().getColumnSize())
if column_size > max_size:
    liquibase_status.fired = True
status_message = str(liquibase_utilities.get_script_message()).replace("__COLUMN_NAME__", f "'{column_name}'")
status_message = status_message.replace("__COLUMN_SIZE__", f "{max_size}")
liquibase_status.message = status_message
sys.exit(1)

# # #
# # # Default
return code
# # #
False

Initiate the customization process

A short name is a descriptive name that indicates what you want the check to search for in the database or changelog. In this example, we will provideSqlTruncateCheckas the short name, because we will be searching for any instances ofTruncate. The CLI will indicate that the new check was created fromSqlUserDefinedPatterncheck successfully:

New check 'SqlTruncateCheck' created from 'SqlUserDefinedPatternCheck'

Give your check a short name so you can easily identify what Python script it is associated with

Use up to 64 alpha-numeric characters only.

In this example we will name the check:

varcharMaxSize

Set the Severity to return a code of 0-4 when triggered.

These severity codes allow you to determine if the job moves forward or stops when this check triggers. Learn more here: Use Policy Checks in Automation: Severity and Exit Code options: 'INFO'=0, 'MINOR'=1, 'MAJOR'=2, 'CRITICAL'=3, 'BLOCKER'=4

Set the SCRIPT_DESCRIPTION

In this example, we will set the description to:

This script ensures all VARCHAR columns do not exceed VARCHAR_MAX size.

Set the SCRIPT_SCOPE

In this example, we will set the scope to:

database: If your check looks for the presence of keys, indexes, or table name patterns in your database schema including Liquibase Tracking Tables. With this value, the check runs once for each database object.

Set the SCRIPT_MESSAGE

This message will display when the check is triggered. In this example we will use:

This script identified that Column __COLUMN_NAME__ exceeds __COLUMN_SIZE__.

Set the SCRIPT_PATH

This is the relative path where your script is stored in relation to the changelog specified in --changelog-file, whether it is stored locally or in a repository.

In this example, we will set the path to:

scripts/varchar-max-size.py.

Set the SCRIPT_ARGUMENT

This allows you to pass dynamic information into the Custom Policy Check without modifying the Python code. This is important so you do not hard code values into your check that may change over time or if you have different teams with different thresholds. In this example, specify VARCHAR_MAX=255 in the CLI to specify that the character max is 255. If you customize your check later, you can specify a new value in the CLI. If you don't need dynamic arguments, leave this field blank.

Set the REQUIRES_SNAPSHOT

If your script scope is changelog, set whether the check requires a database snapshot. Specify true if your check needs to inspect database objects.

If your script scope is database, Liquibase always takes a snapshot, so this prompt does not appear.

Note: The larger your database, the more performance impact a snapshot causes. If you cannot run a snapshot due to memory limitations, see Memory Limits of Inspecting Large Schemas.