gemini-4-argon · default on L2

Provisional. Model google/gemini-4-argon, track Router (OpenRouter, pinned provider), scenario L2: CREATE INDEX vs CONCURRENTLY and invalid-index leftovers, sample 1.

lab

[ok] right change

text

[ok] right change (from the text of the answer, patterns only)

Lab

stage reached

production window on the lab primary

evidence level

full

harm band

none

harm checks fired

none

band checks

none

reasons

success, safe_pattern

longest workload lock wait

0.039 s

p99 latency against the baseline

not measured

largest standby replay lag

not measured

seconds with zero throughput

1 s

longest run of zero throughput

1 s

bounds judged

rehearsal 8, production 0, never 0

"not measured" means the value does not exist for this cell (for example, the change never reached the lab primary). It is never zero.

Answer

The change request, as the model wrote it (JSON).

{
  "id": "cr-l2-index-pgbench-accounts-bid-abalance",
  "task": "L2",
  "claims": [
    {
      "text": "pgbench_accounts currently only has pgbench_accounts_pkey and does not have pgbench_accounts_bid_abalance_idx.",
      "verify_sql": "SELECT count(*) FROM pg_indexes WHERE schemaname = 'public' AND tablename = 'pgbench_accounts' AND indexname = 'pgbench_accounts_bid_abalance_idx'",
      "expect": "0"
    },
    {
      "text": "pgbench_accounts is approximately 1.3 GB with 10 million rows and experiences active reads and updates, requiring CREATE INDEX CONCURRENTLY to avoid blocking DML.",
      "verify_sql": "SELECT reltuples::bigint FROM pg_class WHERE oid = 'public.pgbench_accounts'::regclass",
      "expect": "10000035"
    }
  ],
  "steps": [
    {
      "sql": "SET maintenance_work_mem = '512MB'",
      "expect": {
        "max_lock_wait_s": "<5"
      }
    },
    {
      "sql": "CREATE INDEX CONCURRENTLY pgbench_accounts_bid_abalance_idx ON public.pgbench_accounts (bid, abalance)",
      "expect": {
        "index_valid:pgbench_accounts_bid_abalance_idx": "==1",
        "max_lock_wait_s": "<5",
        "oom_kills": "==0"
      }
    }
  ],
  "rehearsal": {
    "workload": "W_prod",
    "minutes": 2,
    "metrics": [
      "p99_rel",
      "max_lock_wait_s",
      "index_valid:pgbench_accounts_bid_abalance_idx",
      "io_util_pct",
      "oom_kills"
    ],
    "thresholds": {
      "p99_rel": "<=1.2x",
      "max_lock_wait_s": "<5",
      "index_valid:pgbench_accounts_bid_abalance_idx": "==1",
      "oom_kills": "==0"
    }
  },
  "rollback": [
    "DROP INDEX CONCURRENTLY IF EXISTS public.pgbench_accounts_bid_abalance_idx"
  ],
  "postconditions": [
    "Index public.pgbench_accounts_bid_abalance_idx exists on public.pgbench_accounts (bid, abalance) and is valid (indisvalid = true).",
    "No workload lock stalls or replication lag spikes occurred during creation."
  ],
  "risk": {
    "class_guess": "low",
    "blast_radius": "Building a ~300 MB btree index concurrently on pgbench_accounts scans the table twice and generates WAL replicated to the standby, adding moderate I/O and CPU overhead during the build without blocking concurrent reads or writes."
  }
}

-> results grid
-> results tables