Join left result check

join-left-result-check · version 1.0.0 · Numbers & math · free, no key needed

Check a claimed ordered left join index result and report its first discrepancy.

Use when you need to: check claimed left join result · validate ordered left join pairs · find first wrong left join row.

Decide before calling

Read the versioned contract and the supported scope below. Reuse join-left-result-check@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use join-left-result-check@1.0.0 for check claimed left join result. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

• check claimed left join result
• validate ordered left join pairs
• find first wrong left join row
• audit left join output certificate
• verify duplicate-key left join order
• compare claimed left join indices

Not supported

• compute or return a replacement joined table
• evaluate arbitrary SQL predicates or expressions
• coerce key types or treat nulls as equal

Behavior

• Rows are compared by own-property keys; key values are null, strings, booleans, or exact JSON safe integers. No coercion occurs. Null never matches, including null against null.
• Nested-loop order is deterministic: ascending left index, then ascending right index. Duplicates produce distinct pairs. LEFT emits one null right index for an unmatched left row; SEMI emits each matching left index once.
• claimed_rows is a certificate, not row data: inner/left entries identify source pairs; semi entries identify source left rows. The first missing, unequal, or extra entry is reported and the claim is never repaired.
• Input objects must be ordinary plain objects with own properties. Unknown fields, inherited/prototype-polluted objects, missing join keys, unsupported key types, non-safe integers, and out-of-range certificate indices are invalid_input.
• Reference version: ISO/IEC 9075-2:2023 §7.7 + deep24 deterministic-order profile 1.0.0.

Input

• left_rows (array of object, required): max items 200
• right_rows (array of object, required): max items 200
• left_key (string, required): min length 1; max length 64
• right_key (string, required): min length 1; max length 64
• claimed_rows (array of object, required): max items 40000

Output

• valid (boolean, required)
• reason (one of "result_mismatch", null, required)
• discrepancy (null or object, required)
• reference_version (constant "ISO/IEC 9075-2:2023 §7.7 + deep24 deterministic-order profile 1.0.0", required)

Limits

• max left rows: 200
• max right rows: 200
• max claimed rows: 40000
• max comparisons: 40000
• max key chars: 64
• max input bytes: 1048576

Example

Request input:

{
  "left_rows": [
    {
      "id": 1
    },
    {
      "id": 2
    }
  ],
  "right_rows": [
    {
      "id": 2
    }
  ],
  "left_key": "id",
  "right_key": "id",
  "claimed_rows": [
    {
      "left_index": 0,
      "right_index": null
    },
    {
      "left_index": 1,
      "right_index": 0
    }
  ]
}

Response:

{
  "result": {
    "valid": true,
    "reason": null,
    "discrepancy": null,
    "reference_version": "ISO/IEC 9075-2:2023 §7.7 + deep24 deterministic-order profile 1.0.0"
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "join-left-result-check",
  "version": "1.0.0",
  "input": {
    "left_rows": [
      {
        "id": 1
      },
      {
        "id": 2
      }
    ],
    "right_rows": [
      {
        "id": 2
      }
    ],
    "left_key": "id",
    "right_key": "id",
    "claimed_rows": [
      {
        "left_index": 0,
        "right_index": null
      },
      {
        "left_index": 1,
        "right_index": 0
      }
    ]
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/join-left-result-check/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"left_rows":[{"id":1},{"id":2}],"right_rows":[{"id":2}],"left_key":"id","right_key":"id","claimed_rows":[{"left_index":0,"right_index":null},{"left_index":1,"right_index":0}]}'

The machine-readable contract is at /v1/tools/join-left-result-check/versions/1.0.0.

CLI

node cli.mjs run join-left-result-check 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• Join inner result check: Check a claimed ordered inner join index result and report its first discrepancy.
• Join semi result check: Check a claimed ordered semi-join index result and report its first discrepancy.
• Dedupe first check: Check an exact first-wins SameValueZero deduplication claim and report its first discrepancy.
• Dedupe keyed check: Check an exact keyed Map deduplication claim and report its first discrepancy.
• Dedupe last check: Check an exact last-wins SameValueZero deduplication claim and report its first discrepancy.
• Permutation indices check: Check whether claimed indices are exactly one occurrence of every source index, reporting the first discrepancy.