feat: add native JSON type support for SQL Server 2025 by dlevy-msft-sql · Pull Request #315 · microsoft/go-mssqldb

dlevy-msft-sql · 2026-01-31T00:19:41Z

Adds native JSON type support for SQL Server 2025 Preview, enabling proper handling of the new JSON data type.

Features

Add JSON token type (typeJson = 0xF4) and type parsing
Add featureExtJsonSupport for TDS login negotiation
Track JSON support capability in session state
Sort feature extensions for deterministic login packets
Comprehensive tests for JSON type scanning

Usage

JSON data is returned as string containing the JSON document. Supports scanning into:

string
[]byte
mssql.NullJSON (wraps json.RawMessage)
Types implementing sql.Scanner

Requirements

SQL Server 2025 Preview or later

Split from #306 for easier review

Copilot

Pull request overview

Adds end-to-end support for SQL Server 2025’s native JSON type, including TDS login feature negotiation, session capability tracking, JSON parameter declaration behavior with fallback, and tests/docs.

Changes:

Introduces typeJson handling in TDS type parsing/metadata and SQL type name/decl generation.
Adds featExtJSONSUPPORT negotiation in LOGIN7 and tracks jsonSupported on the session.
Adds mssql.JSON / mssql.NullJSON parameter types plus a comprehensive JSON test suite and documentation updates.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
`types.go`	Adds JSON type ID, PLP decode path, and type metadata helpers (decl/name/length/prec-scale).
`token.go`	Parses server ACK payload for JSON feature extension.
`tds.go`	Adds JSON feature-ext request/ACK handling, session flag, and deterministic feature-ext ordering.
`tds_login_test.go`	Updates expected LOGIN7 hex blobs to include JSON feature extension and new deterministic ordering.
`mssql_go19.go`	Adds `JSON`/`NullJSON` types and parameter encoding with JSON-decl fallback logic.
`mssql.go`	Ensures JSON parameters are handled before `driver.Valuer` processing.
`json_test.go`	Adds unit + integration tests for JSON parameter behavior, fallback behavior, and declarations.
`README.md`	Documents JSON parameter types, compatibility/fallback behavior, and limitations.
`CHANGELOG.md`	Adds release note entry for JSON support.

Copilot

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 4 comments.

codecov-commenter · 2026-01-31T01:39:33Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.62%. Comparing base (65e137f) to head (567c8de).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #315       +/-   ##
===========================================
+ Coverage   80.62%   96.62%   +15.99%     
===========================================
  Files          35       92       +57     
  Lines        6910    74509    +67599     
===========================================
+ Hits         5571    71991    +66420     
- Misses       1068     2183     +1115     
- Partials      271      335       +64

Flag	Coverage Δ
unittests	`96.55% <100.00%> (?)`

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
bulkcopy.go	`64.40% <100.00%> (+1.35%)`	⬆️
mssql.go	`89.43% <100.00%> (-0.02%)`	⬇️
mssql_go19.go	`96.56% <100.00%> (+1.58%)`	⬆️
tds.go	`70.58% <100.00%> (+1.23%)`	⬆️
token.go	`70.09% <100.00%> (+0.56%)`	⬆️
types.go	`82.39% <100.00%> (+0.31%)`	⬆️

... and 57 files with indirect coverage changes

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

Copilot

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 4 comments.

Copilot

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 4 comments.

Copilot

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Copilot reviewed 14 out of 17 changed files in this pull request and generated 1 comment.

Copilot

Pull request overview

Copilot reviewed 14 out of 17 changed files in this pull request and generated 2 comments.

Copilot

Pull request overview

Copilot reviewed 14 out of 17 changed files in this pull request and generated 2 comments.

Copilot

Pull request overview

Copilot reviewed 14 out of 17 changed files in this pull request and generated 1 comment.

Copilot

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Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Copilot

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Copilot

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Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Copilot

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Copilot

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Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

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Copilot

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Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Copilot

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Copilot

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Copilot

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Copilot

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Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

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Copilot reviewed 10 out of 10 changed files in this pull request and generated no new comments.

Copilot

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Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Copilot

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Copilot

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

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Copilot reviewed 10 out of 10 changed files in this pull request and generated no new comments.

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Copilot reviewed 10 out of 10 changed files in this pull request and generated no new comments.

dlevy-msft-sql self-assigned this Jan 31, 2026

dlevy-msft-sql added enhancement New feature or request Area - data types Issues related to data types Size: S Small issue (less than one week effort, less than 250 lines of code) labels Jan 31, 2026

dlevy-msft-sql requested a review from Copilot January 31, 2026 00:20

Copilot started reviewing on behalf of dlevy-msft-sql January 31, 2026 00:20 View session

dlevy-msft-sql mentioned this pull request Jan 31, 2026

FEATURE: SQL 2025 Native JSON Support #306

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