Case Sensitivity on Computed Columns

Oct 13, 2025 by talynt.org 45 views

When working with Entity Framework (EF) and Postgres, comparing the EF model against the Postgres database can be a challenging task. While tools like SchemaCompare can help streamline this process, there are several issues that can arise, particularly when dealing with specific Postgres features and limitations. In this article, we will explore three common issues that can occur when comparing EF models against Postgres and discuss potential solutions.

Column Length Limit

One of the primary issues that can arise when comparing EF models against Postgres is the column length limit. Postgres has a limit of 63 bytes/59 characters for column names due to the use of UTF-8 encoding. However, EF truncates column names to fit within this limit, which can lead to mismatches between the expected and found column names.

For example, if a column name is "very_long_column_name" and EF truncates it to "very_long_column", the object will exist in the model, but the name will not match the actual column name in the Postgres database.

-- Postgres column name
CREATE TABLE mytable (
    very_long_column_name VARCHAR(255)
);

-- EF truncated column name
public class MyTable
{
    public string very_long_column { get; set; }
}

To address this issue, we can add two additional properties to the CompareEfSqlConfig class: CaseSensitivity and MaxIdentifierLength. These properties can be used in the comparer to match on case and/or substring, allowing for more accurate comparisons between the EF model and the Postgres database.

Case Sensitivity on Computed Columns

Another issue that can arise when comparing EF models against Postgres is case sensitivity on computed columns. Computed columns in Postgres can have different casing than their equivalent columns in the EF model, leading to mismatches.

For example, a computed column in Postgres might be defined as NOW() while the equivalent column in the EF model is defined as now(). This difference in casing can cause the comparer to fail, even if the underlying data is identical.

-- Postgres computed column
CREATE TABLE mytable (
    created_at TIMESTAMP DEFAULT NOW()
);

-- EF computed column
public class MyTable
{
    public DateTime created_at { get; set; }
}

To address this issue, we can modify the comparer to ignore case differences when comparing computed columns. This can be achieved by adding a check for case sensitivity in the comparer and adjusting the comparison accordingly.

Type Conversion in Postgres

The final issue that can arise when comparing EF models against Postgres is type conversion in Postgres. Postgres has a number of built-in data types, including jsonb and date, which can be used to store complex data. However, when comparing these data types against their equivalent types in the EF model, issues can arise due to differences in type conversion.

For example, a computed column in Postgres might be defined as completed_at AT TIME ZONE 'America/Los_Angeles'::date while the equivalent column in the EF model is defined as completed_at AT TIME ZONE 'America/Los_Angeles'::text. This difference in type conversion can cause the comparer to fail, even if the underlying data is identical.

-- Postgres computed column
CREATE TABLE mytable (
    completed_at TIMESTAMP AT TIME ZONE 'America/Los_Angeles'::date
);

-- EF computed column
public class MyTable
{
    public DateTime completed_at { get; set; }
}

To address this issue, we can modify the comparer to handle type conversion differences in Postgres. This can be achieved by adding a check for type conversion in the comparer and adjusting the comparison accordingly.

Potential Solutions

To address the issues discussed above, we can modify the CompareEfSqlConfig class to include two additional properties: CaseSensitivity and MaxIdentifierLength. These properties can be used in the comparer to match on case and/or substring, allowing for more accurate comparisons between the EF model and the Postgres database.

We can also modify the comparer to handle type conversion differences in Postgres by adding a check for type conversion in the comparer and adjusting the comparison accordingly.

public class CompareEfSqlConfig
{
    public bool CaseSensitivity { get; set; }
    public int MaxIdentifierLength { get; set; }
}

public class EfSqlComparer
{
    public bool Compare(EfSqlConfig expected, EfSqlConfig found)
    {
        // Check for case sensitivity
        if (expected.CaseSensitivity)
        {
            // Ignore case differences
        }

        // Check for max identifier length
        if (expected.MaxIdentifierLength > 0)
        {
            // Truncate identifier to max length
        }

        // Handle type conversion differences
        if (expected.TypeConversion != found.TypeConversion)
        {
            // Adjust comparison accordingly
        }

        // Compare remaining properties
        // ...
    }
}

Conclusion

In our previous article, we discussed three common issues that can arise when comparing EF models against Postgres: column length limit, case sensitivity on computed columns, and type conversion in Postgres. In this article, we will answer some frequently asked questions related to these issues and provide additional guidance on how to address them.

Q: What is the column length limit in Postgres?

A: The column length limit in Postgres is 63 bytes/59 characters due to the use of UTF-8 encoding. This means that column names longer than 63 bytes/59 characters will be truncated by Postgres.

Q: How can I address the column length limit issue?

A: To address the column length limit issue, you can add two additional properties to the CompareEfSqlConfig class: CaseSensitivity and MaxIdentifierLength. These properties can be used in the comparer to match on case and/or substring, allowing for more accurate comparisons between the EF model and the Postgres database.

Q: What is case sensitivity on computed columns?

A: Case sensitivity on computed columns refers to the difference in casing between computed columns in Postgres and their equivalent columns in the EF model. For example, a computed column in Postgres might be defined as NOW() while the equivalent column in the EF model is defined as now().

Q: How can I address the case sensitivity on computed columns issue?

A: To address the case sensitivity on computed columns issue, you can modify the comparer to ignore case differences when comparing computed columns. This can be achieved by adding a check for case sensitivity in the comparer and adjusting the comparison accordingly.

Q: What is type conversion in Postgres?

A: Type conversion in Postgres refers to the process of converting data from one type to another. For example, a computed column in Postgres might be defined as completed_at AT TIME ZONE 'America/Los_Angeles'::date while the equivalent column in the EF model is defined as completed_at AT TIME ZONE 'America/Los_Angeles'::text.

Q: How can I address the type conversion in Postgres issue?

A: To address the type conversion in Postgres issue, you can modify the comparer to handle type conversion differences in Postgres. This can be achieved by adding a check for type conversion in the comparer and adjusting the comparison accordingly.

Q: What are some best practices for comparing EF models against Postgres?

A: Some best practices for comparing EF models against Postgres include:

Using a comparer that can handle case sensitivity and type conversion differences
Adding two additional properties to the CompareEfSqlConfig class: CaseSensitivity and MaxIdentifierLength
Modifying the comparer to ignore case differences when comparing computed columns
Modifying the comparer to handle type conversion differences in Postgres

Q: Can I use a different comparer for comparing EF models against Postgres?

A: Yes, you can use a different comparer for comparing EF models against Postgres. However, you will need to ensure that the comparer can handle the specific issues related to Postgres, such as case sensitivity and type conversion differences.

Q: How can I troubleshoot issues when comparing EF models against Postgres?

A: To troubleshoot issues when comparing EF models against Postgres, you can:

Use a comparer that provides detailed error messages
Add logging to the comparer to track the comparison process
Use a debugger to step through the comparison process and identify issues

Conclusion

Comparing EF models against Postgres can be a challenging task, particularly when dealing with specific Postgres features and limitations. By understanding the issues that can arise and modifying the comparer to handle these issues, we can improve the accuracy of comparisons between the EF model and the Postgres database. By following the best practices outlined in this article, you can ensure that your comparer is able to handle the specific issues related to Postgres and provide accurate comparisons.