fix load data report 'unsupported cast from json to JSON' by robll-v1 · Pull Request #23825 · matrixorigin/matrixone

robll-v1 · 2026-03-09T10:46:29Z

What type of PR is this?

Which issue(s) this PR fixes:

What this PR does / why we need it:

Fix LOAD DATA ... PARALLEL 'TRUE' failure on tables with JSON columns and irregular indexes (for example IVFFLAT).

This change adds a safe identity cast path for JSON -> JSON, which prevents parallel load from failing with:

internal error: unsupported cast from json to JSON
Root Cause
For LOAD DATA on tables with irregular indexes, the planner may fall back to the legacy load path.
In the parallel branch, that path introduces an extra cast layer. For JSON columns, execution could reach the generic jsonToOthers() cast path.

Before this change, jsonToOthers() did not handle JSON -> JSON, so parallel load could fail even though the source and target types were both JSON.

Fix
Add an explicit identity cast branch for JSON -> JSON in pkg/sql/plan/function/func_cast.go
Copy JSON values safely via GetStrValue()/AppendBytes() instead of using a generic fixed-type duplication path
Add a regression unit test for JSON -> JSON cast in pkg/sql/plan/function/func_cast_test.go
Impact
This fixes parallel LOAD DATA for scenarios like:

JSON column present
IVFFLAT index present
LOAD DATA URL S3OPTION ... PARALLEL 'TRUE'
The fix is intentionally minimal and does not change the broader legacy load path behavior.

Files Changed
pkg/sql/plan/function/func_cast.go
pkg/sql/plan/function/func_cast_test.go
Validation
Unit Test
go test ./pkg/sql/plan/function -run 'TestCastJsonTo(Json|Numeric)' -count=1
Build
make build
Runtime Verification
Verified with a real LOAD DATA URL S3OPTION ... PARALLEL 'TRUE' flow against local MinIO.

Scenario:

table with JSON column
VECF64 column
IVFFLAT index
large CSV file (parallel path actually triggered)
Result:

before fix: internal error: unsupported cast from json to JSON
after fix: parallel load succeeded

Notes
This PR is a minimal functional fix to unblock the reported issue.
If needed, the legacy parallel LOAD DATA cast path can be further cleaned up in a follow-up change.

CLAassistant · 2026-03-09T10:46:39Z

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qodo-code-review · 2026-03-09T10:46:47Z

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Review Summary by Qodo

Fix JSON to JSON cast in parallel LOAD DATA operations

🐞 Bug fix

Walkthroughs

Description

• Add identity cast path for JSON to JSON conversion
• Prevent parallel LOAD DATA failures on tables with JSON columns
• Use safe value copying via GetStrValue()/AppendBytes() methods
• Add regression test for JSON to JSON cast operation

Diagram

flowchart LR
  A["LOAD DATA PARALLEL on JSON column"] -->|encounters irregular index| B["Legacy load path with cast layer"]
  B -->|JSON to JSON cast| C["jsonToOthers function"]
  C -->|before fix| D["❌ unsupported cast error"]
  C -->|after fix| E["✓ Identity cast with safe copy"]
  E --> F["Parallel load succeeds"]

File Changes

1. pkg/sql/plan/function/func_cast.go 🐞 Bug fix +9/-0

Add JSON to JSON identity cast handler

• Add explicit case handler for types.T_json in jsonToOthers() function
• Implement identity cast using GetStrValue() and AppendBytes() for safe JSON value copying
• Handle null values correctly during the cast operation

pkg/sql/plan/function/func_cast.go

2. pkg/sql/plan/function/func_cast_test.go 🧪 Tests +16/-0

Add regression test for JSON to JSON cast

• Add new test function TestCastJsonToJson() for JSON to JSON casting
• Test with multiple JSON values including objects, arrays, and null
• Verify cast preserves original encoded JSON data

pkg/sql/plan/function/func_cast_test.go

qodo-code-review · 2026-03-09T10:46:48Z

Code Review by Qodo

🐞 Bugs (1) 📘 Rule violations (0) 📎 Requirement gaps (0)

1. Planner rejects JSON→JSON 🐞 Bug ✓ Correctness

Description

jsonToOthers() now implements JSON→JSON at execution time, but CAST overload resolution still
rejects (json,json) because supportedTypeCast for T_json omits T_json. As a result, binder-generated
CAST expressions can fail in GetFunctionByName("cast", [json,json]) even though the execution path
now supports it.

Code

pkg/sql/plan/function/func_cast.go[R1834-1842]

+	case types.T_json:
+		rs := vector.MustFunctionResult[types.Varlena](result)
+		for i := uint64(0); i < uint64(length); i++ {
+			v, null := source.GetStrValue(i)
+			if err := rs.AppendBytes(v, null); err != nil {
+				return err
+			}
+		}
+		return nil

Evidence
Execution support was added in jsonToOthers() for toType.Oid==T_json, but the CAST operator’s type
check consults IfTypeCastSupported(), which only returns true when the target OID is present in
supportedTypeCast[source]. supportedTypeCast[types.T_json] does not include types.T_json, so
IfTypeCastSupported(T_json,T_json) is false; the binder always constructs CAST expressions by
calling function.GetFunctionByName("cast", argsType), so planning/binding a JSON→JSON cast can fail
before reaching the new runtime path. The new unit test calls NewCast directly (bypassing
binder/type-check), so it doesn’t cover this mismatch.
pkg/sql/plan/function/func_cast.go[1830-1846]
pkg/sql/plan/function/func_cast.go[363-369]
pkg/sql/plan/function/func_cast.go[411-420]
pkg/sql/plan/function/list_operator.go[2549-2560]
pkg/sql/plan/base_binder.go[135-146]
pkg/sql/plan/base_binder.go[2401-2410]
pkg/sql/plan/function/func_testcase.go[141-142]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

### Issue description
`jsonToOthers()` now supports JSON→JSON casts at execution time, but CAST overload resolution still rejects `(T_json -&gt; T_json)` because `supportedTypeCast[types.T_json]` does not include `types.T_json`. This can cause explicit `CAST(json_expr AS JSON)` (and any binder-inserted JSON→JSON cast) to fail during `GetFunctionByName(&quot;cast&quot;, ...)` even though runtime can execute it.

### Issue Context
- CAST operator resolution uses `IfTypeCastSupported(inputs[0].Oid, inputs[1].Oid)`.
- `IfTypeCastSupported` only returns true when the target OID is present in `supportedTypeCast[source]`.
- Unit tests added in this PR call `NewCast` directly and do not validate overload resolution/binding.

### Fix Focus Areas
- pkg/sql/plan/function/func_cast.go[363-369]
- pkg/sql/plan/function/func_cast.go[411-420]
- pkg/sql/plan/function/list_operator.go[2549-2560]
- pkg/sql/plan/function/func_cast_test.go[2491-2505]

### Suggested fix
1. Update `supportedTypeCast` for `types.T_json` to include `types.T_json` (identity cast).
2. Add a regression test that ensures overload resolution succeeds for JSON→JSON, e.g. calling `function.GetFunctionByName(ctx, &quot;cast&quot;, []types.Type{types.T_json.ToType(), types.T_json.ToType()})` and asserting it returns successfully (or asserting `IfTypeCastSupported(types.T_json, types.T_json)` is true).

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pkg/sql/plan/function/func_cast.go

mergify · 2026-03-11T10:28:05Z

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mergify · 2026-03-11T11:23:43Z

Merge Queue Status

✅ Entered queue — 2026-03-11 11:23 UTC · Rule: main
✅ Checks passed · in-place
✅ Merged — 2026-03-11 11:23 UTC · at 82057606ec46eec646cba81a31590d31db6e3dc8

This pull request spent 11 seconds in the queue, with no time running CI.

Required conditions to merge

fix load data report 'unsupported cast from json to JSON'

53309ee

robll-v1 requested review from aunjgr and ouyuanning as code owners March 9, 2026 10:46

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pkg/sql/plan/function/func_cast.go Show resolved Hide resolved

updated cast overload resolution

214572f

robll-v1 temporarily deployed to ci March 10, 2026 03:22 — with GitHub Actions Inactive

aunjgr approved these changes Mar 11, 2026

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Merge branch 'main' into issue/23822

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fix load data report 'unsupported cast from json to JSON'#23825

fix load data report 'unsupported cast from json to JSON'#23825
mergify[bot] merged 3 commits intomatrixorigin:mainfrom
robll-v1:issue/23822

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robll-v1 commented Mar 9, 2026

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