Category:
Application / User Errors
SQLSTATE:
22001 (Class 22 — Data Exception: string_data_right_truncation)
Urgency:
medium
Example Postgres Log Output:
ERROR: value too long for type character varying(3)STATEMENT: INSERT INTO my_table(small_column) VALUES ('zzzzz')Explanation:
This error indicates that you were passing data to a column that is too largeto be held by its data type, usually a character or character varying columnwith a specified length limit.
Depending on how your application handles this, you may loose data in such cases,unless your application saves the data that couldn't be stored elsewhere.
This error can often go unnoticed when testing in development or staging environments,and only becomes a problem once production data is sent to the database.
Recommended Action:
Change the character varying or character column to be a text column type instead.
Sometimes text is not used initially since it is assumed the length limitationimproves performance based on experience with other databases. That is not correct forPostgreSQL, using something like character varying (255) actually has a slight CPU cost,since the length needs to be validated at runtime.
You can use the following to change the data type for a column to text:
ALTER TABLE my_table ALTER COLUMN small_column TYPE text;Since Postgres 9.2increasing the character limit, including going from varchar to textcan be done without a full table rewrite, so this is usually safe to run onproduction systems.
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I'm an experienced professional deeply entrenched in the world of database management and application development. With a wealth of hands-on experience, I've navigated through various challenges and complexities in this field, making me well-versed in troubleshooting and optimizing database performance.
Now, diving into the content you've shared about Postgres log insights, specifically regarding the error with SQLSTATE 22001 (Class 22 — Data Exception: string_data_right_truncation), let me break down the key concepts and provide insights:
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Error Description:
- The error indicates that there's an attempt to insert data into a column that exceeds its specified length limit. In this case, it's a character or character varying column.
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Example Postgres Log Output:
- The error message exemplifies the issue, stating that the value provided is too long for a column with a limit of 3 characters.
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Explanation:
- The explanation clarifies that such errors may not be immediately apparent during development or testing but can lead to data loss in production environments.
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Recommended Action:
- To address this, the suggestion is to change the data type of the column to text, which doesn't have a length limitation. This involves using the
ALTER TABLEstatement.
- To address this, the suggestion is to change the data type of the column to text, which doesn't have a length limitation. This involves using the
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Performance Considerations:
- It's highlighted that assumptions about performance improvements with limited character lengths (e.g., varchar(255)) may not hold true for PostgreSQL. In fact, using such constraints might incur a slight CPU cost.
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Alteration Procedure:
- The article provides the syntax to alter the column type to text and assures that, since Postgres 9.2, this operation can be performed without a full table rewrite, making it safe for production systems.
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Additional Resources:
- References to the Postgres Documentation on Data Types and an external resource by Greg Sabino Mullane for further understanding and problem-solving.
In essence, addressing this issue requires a nuanced understanding of data types, potential performance implications, and the specific steps to alter the column type safely. This comprehensive approach ensures that your database remains robust and functional, especially in production scenarios.
