Database Index Selectivity / Cardinality Estimator implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t5-079

Effect

Computation or source lookup only

Input and validation requirements

The formulas have undefined results when total_rows or distinct_values is zero, and the specification does not state input validation for zero or for distinct_values greater than total_rows. The specification also does not define a threshold or rule for the requested index-usefulness verdict, so that output cannot be reliably produced.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "total_rows": 1000000,
    "distinct_values": 1000000
  },
  "expected_outputs": {
    "selectivity_ratio": 1,
    "estimated_rows_per_lookup": 1,
    "index_usefulness_verdict": "UNDEFINED_BY_SPEC"
  },
  "working": "selectivity_ratio = distinct_values / total_rows = 1000000 / 1000000 = 1. estimated_rows_per_lookup = total_rows / distinct_values = 1000000 / 1000000 = 1 row per lookup. The index-usefulness verdict has no specified formula or threshold."
}

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche5/tranche5-results.json