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Support XML data type for MSSQL#3006

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Support XML data type for MSSQL#3006
Copilot wants to merge 5 commits intomainfrom
copilot/support-xml-data-type-mssql

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Copilot AI commented Dec 4, 2025 •
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Why make this change?

Closes #2698

SQL Server's XML data type (supported since SQL Server 2005) was not recognized by DAB, preventing use of tables with XML columns.

What is this change?

Treat XML as a string type, consistent with how SQL Server emits it via FOR JSON:

  • SqlTypeConstants.cs: Mark xml as supported (true)
  • TypeHelper.cs: Map SqlDbType.Xml → typeof(string)
  • DatabaseSchema-MsSql.sql: Add xml_types column to type_table with test data for integration testing

DAB passes XML as string in both directions; SQL Server handles validation.

How was this tested?

  • Integration Tests
  • Unit Tests

Existing CLRtoJsonValueTypeUnitTests now validates (xml,True) test case passes. Added XML column to type_table in MsSql test database schema with various XML test data to enable integration testing of XML data type operations.

Sample Request(s)

POST /documents
Content-Type: application/json

{
  "id": 1,
  "metadata": "<author>admin</author>"
}

Response:

{
  "value": [
    {
      "id": 1,
      "metadata": "<author>admin</author>"
    }
  ]
}
Original prompt

This section details on the original issue you should resolve

<issue_title>[Enhancement]: Support XML data type for MSSQL</issue_title>
<issue_description># XML data type

In SQL Server and Azure SQL Database, the XML data type stores structured XML content. Unlike the JSON data type, XML has been supported since SQL Server 2005 and includes native indexing, query, and validation capabilities.

CREATE TABLE documents (
    id INT PRIMARY KEY,
    metadata XML  -- a native XML document
)

FOR JSON support

When used with FOR JSON, SQL Server will emit the XML content as a string, not a parsed structure. This is because XML is not directly translatable to JSON without transformation.

SELECT id, metadata FROM documents FOR JSON AUTO;

Returns:

[
  {
    "id": 1,
    "metadata": "<doc><type>report</type><author>admin</author></doc>"
  }
]

Inserting XML

INSERT INTO documents (id, metadata)
VALUES (
    1,
    '<doc><type>report</type><author>admin</author></doc>'
);
  • The XML must be passed as a valid string literal.
  • SQL Server will parse and validate the XML at runtime.
  • You can define an XML schema collection for strict validation if needed.

Data API builder behavior

Data API builder (DAB) should treat the XML column as a string in both directions.

Query operations

DAB will expose XML values as string content in REST responses:

{
  "value": [
    {
      "id": 1,
      "metadata": "<doc><type>report</type><author>admin</author></doc>"
    }
  ]
}

Mutation operations

Whether creating or updating, input must be a string containing valid XML:

POST /documents
Content-Type: application/json

{
  "id": 2,
  "metadata": "<doc><type>memo</type><author>guest</author></doc>"
}

XML Considerations

  1. SQL Server will validate the string as well-formed XML before storing.
  2. DAB does not parse or format XML—it treats the field as a text payload.
  3. XML schema collections can be applied to restrict content if required.</issue_description>

Comments on the Issue (you are @copilot in this section)

@JerryNixon Basically, treat it as string.

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@JerryNixon
Add support for XML data type in MSSQL by treating it as string
353b1ea 
Co-authored-by: JerryNixon <1749983+JerryNixon@users.noreply.github.com>
Copilot AI changed the title [WIP] Add support for XML data type in MSSQL Support XML data type for MSSQL Dec 4, 2025
Copilot AI requested a review from JerryNixon December 4, 2025 03:23
@JerryNixon JerryNixon moved this from Todo to Review In Progress in Data API builder Dec 4, 2025
@JerryNixon JerryNixon added this to the Dec 2025 milestone Dec 4, 2025
@JerryNixon JerryNixon marked this pull request as ready for review December 4, 2025 05:08
Copilot AI review requested due to automatic review settings December 4, 2025 05:08
Copilot AI reviewed Dec 4, 2025
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Pull request overview

This PR adds support for SQL Server's XML data type by treating it as a string type, consistent with how SQL Server emits XML content via FOR JSON.

  • Marks XML as a supported SQL type in SqlTypeConstants.cs
  • Maps SqlDbType.Xml to typeof(string) in TypeHelper.cs

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File Description
src/Core/Models/SqlTypeConstants.cs Marks xml type as supported (changed from false to true)
src/Core/Services/TypeHelper.cs Adds mapping from SqlDbType.Xml to typeof(string) in the type conversion dictionary

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@JerryNixon JerryNixon requested a review from Copilot December 4, 2025 18:07
Copilot AI reviewed Dec 4, 2025
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Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

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@JerryNixon
Add XML column to type_table in MsSql test database schema
3ce04b9 
Co-authored-by: JerryNixon <1749983+JerryNixon@users.noreply.github.com>
@aaronburtle aaronburtle self-assigned this Dec 15, 2025
@RubenCerna2079 RubenCerna2079 self-assigned this Dec 16, 2025
@RubenCerna2079
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RubenCerna2079 commented Dec 16, 2025

/azp run

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azure-pipelines bot commented Dec 16, 2025

Azure Pipelines successfully started running 6 pipeline(s).

@Aniruddh25 Aniruddh25 modified the milestones: Dec 2025, Feb 2026 Jan 31, 2026
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+1 more reviewer

@JerryNixon JerryNixon JerryNixon approved these changes

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Assignees

@JerryNixon JerryNixon

@RubenCerna2079 RubenCerna2079

@aaronburtle aaronburtle

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Projects

Data API builder
Status: Review In Progress

Milestone

Feb 2026

Development

Successfully merging this pull request may close these issues.

[Enhancement]: Support XML data type for MSSQL Host DAB in AKS

5 participants

@RubenCerna2079 @JerryNixon @Aniruddh25 @aaronburtle