[Bug]: MySQL JSON column values shown as NULL in data grid by midasism · Pull Request #107 · debba/tabularis

midasism · 2026-03-28T04:04:53Z

Summary

MySQL JSON type columns display null in the data grid even when they contain valid JSON data
JSON columns in the sidebar row editor display [object Object] and cannot be edited
Root cause: extract_value in mysql/extract.rs has no dedicated JSON branch — unlike the PostgreSQL driver which explicitly handles serde_json::Value, the MySQL driver falls through all try_get attempts and hits the fallback Null return
Additionally, update_record and insert_record reject Object/Array values with "Unsupported Value type" error

Changes

Backend (Rust)

src-tauri/Cargo.toml: add "json" to sqlx features — this registers Decode<MySql> for serde_json::Value
src-tauri/src/drivers/mysql/extract.rs: add a col_type == "JSON" branch before the GEOMETRY block, mirroring the PostgreSQL approach with an additional raw-byte fallback for edge cases
src-tauri/src/drivers/mysql/mod.rs: handle Object/Array values in update_record and insert_record via CAST(? AS JSON) instead of returning an error

Frontend (React/TypeScript)

src/utils/json.ts (new): isJsonColumn, formatJsonForEditor, validateJson, parseJsonEditorValue utility functions
src/components/ui/JsonInput.tsx (new): dedicated JSON editor component with:
- Pretty-printed textarea display
- Real-time JSON validation with visual indicator (green ✓ / red ✗)
- One-click format button
- Error detail display
src/components/ui/FieldEditor.tsx: wire JsonInput for JSON/JSONB column types in the sidebar editor
src/components/ui/DataGrid.tsx: double-click on JSON cells opens the sidebar editor instead of inline editing
src/i18n/locales/{en,zh,it,es}.json: add jsonInput translation keys

Test plan

Connect to a MySQL 8.0+ database with a table containing a JSON column
Verify JSON values are rendered correctly in the data grid (not shown as null)
Verify actual NULL JSON values still display as null
Double-click a JSON cell opens the sidebar with a formatted JSON editor
Edit JSON in the sidebar editor with real-time validation
Submit edited JSON values back to the database successfully
Verify CSV/JSON export includes correct JSON values
Verify PostgreSQL and SQLite JSON handling is unaffected

MySQL JSON columns were not being decoded properly because `extract_value` lacked a dedicated JSON branch. Unlike PostgreSQL which already handles `serde_json::Value`, the MySQL driver fell through every `try_get` attempt and returned `Null`. - Enable the sqlx `json` feature so `Decode<MySql>` is implemented for `serde_json::Value` - Add an explicit JSON type branch in `mysql/extract.rs` that first tries `try_get::<serde_json::Value>`, then falls back to raw-byte decoding and manual JSON parsing Made-with: Cursor

kilo-code-bot · 2026-03-28T04:05:54Z

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (8 files)

src-tauri/src/drivers/mysql/mod.rs - Added JSON Object/Array handling in update_record and insert_record using CAST(? AS JSON) (lines 521-526, 612-617)
src/components/ui/DataGrid.tsx - Added JSON column handling to open sidebar editor on double-click (lines 306-314)
src/components/ui/FieldEditor.tsx - Wired JsonInput component for JSON/JSONB column types (lines 100-106)
src/components/ui/JsonInput.tsx - New JSON editor component with validation, formatting, and real-time error feedback
src/utils/json.ts - New utility functions: isJsonColumn, formatJsonForEditor, validateJson, parseJsonEditorValue
src/i18n/locales/en.json, es.json, it.json, zh.json - Added jsonInput translation keys

Notes:

The MySQL JSON handling correctly uses CAST(? AS JSON) syntax for proper type conversion
The JsonInput component provides good UX with real-time validation, format button, and visual indicators
Implementation follows existing patterns (BlobInput, GeometryInput) for specialized column types
Error handling is consistent with the rest of the codebase

_{Reviewed by kimi-k2.5-0127 · 115,816 tokens}

JSON columns in the sidebar row editor previously displayed "[object Object]" and were not editable. This adds a dedicated JsonInput component with real-time validation, pretty-print formatting, and proper read/write support for JSON values. - Add `src/utils/json.ts` with isJsonColumn, formatJsonForEditor, validateJson, and parseJsonEditorValue helpers - Add `src/components/ui/JsonInput.tsx` — textarea-based JSON editor with format button and valid/invalid indicator - Wire JsonInput into FieldEditor for JSON/JSONB columns - DataGrid: double-click on JSON cells opens sidebar editor - Backend: update_record and insert_record now accept Object/Array values via CAST(? AS JSON) instead of rejecting them - Add i18n keys for en, zh, it, es Made-with: Cursor

debba · 2026-03-28T07:03:45Z

Hi!
Thanks for your contribution!

Are you already working on it?
Because I did some tests, but always continue to see JSON columns as NULL and inside columns view, I can see the column as LONGTEXT

midasism · 2026-03-28T10:15:28Z

Hi @debba, thanks for testing!

I verified the fix works correctly on MySQL 8.0.42. The limit_info (JSON column) renders properly in the data grid — showing values like {"minMonths":10}, {"lookbackDays":365,"serviceTypeIds":[18,20]} etc., instead of null.

The key difference is likely the MySQL variant you're testing on:

On MySQL 8.0+, JSON is a native column type. sqlx reports type_info().name() as "JSON", and String::compatible() does not include ColumnType::Json — which is exactly why the original code falls through to Null. This fix adds a dedicated "JSON" branch with try_get::<serde_json::Value>.
On MariaDB, JSON is an alias for LONGTEXT (MariaDB docs). sqlx returns "LONGTEXT" instead of "JSON", so the new branch won't match. However, on MariaDB the existing try_get::<String> path should already work since LONGTEXT maps to ColumnType::LongBlob (without BINARY flag), which is in String::compatible().

Could you confirm which database you're testing on? You can check with SELECT VERSION(). If it contains "MariaDB", that would explain the LONGTEXT type you're seeing — and in that case the JSON display issue on MariaDB would be a separate bug with a different root cause.

My test environment:

MySQL 8.0.42
DDL:

CREATE TABLE `tapp_appointment_recommend_rule_limit` (
  `id` int NOT NULL AUTO_INCREMENT,
  `limit_type` tinyint NOT NULL,
  `limit_info` json NOT NULL,
  `delete_flag` tinyint NOT NULL DEFAULT 0,
  `rule_id` int NOT NULL,
  `created` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `modified` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`)
);

debba · 2026-03-28T13:34:58Z

Sorry, you're right.
I'll merge it, thanks a lot :)

debba · 2026-03-29T09:52:21Z

I added my thanks here:

https://tabularis.dev/blog/v0912-tokio-postgres-minimax-json-editor

debba merged commit 318dbc8 into debba:main Mar 28, 2026
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[Bug]: MySQL JSON column values shown as NULL in data grid#107

[Bug]: MySQL JSON column values shown as NULL in data grid#107
debba merged 2 commits intodebba:mainfrom
midasism:fix/mysql-json-column-shown-as-null

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midasism commented Mar 28, 2026 •

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