/** Counters taken in one shot from `pg_stat_activity`. */
export interface DbPressureCounters {
    connections: number;
    idleInTxn: number;
    oldestIdleTxnS: number;
    maxSameQuery: number;
    trivialQueryMs: number;
}
export type DbPressure = ({
    measured: true;
    warnings: string[];
} & DbPressureCounters) | {
    measured: false;
    reason: string;
};
export declare const MAX_IDLE_TXN_AGE_S = 60;
export declare const MAX_TRIVIAL_QUERY_MS = 1000;
export declare const MAX_SAME_QUERY_CONCURRENCY = 10;
export declare const DB_PRESSURE_SQL = "\nSELECT\n  count(*)::int AS connections,\n  count(*) FILTER (WHERE state = 'idle in transaction')::int AS idle_in_txn,\n  coalesce(round(max(extract(epoch from (now() - state_change)))\n    FILTER (WHERE state = 'idle in transaction'))::int, 0) AS oldest_idle_txn_s,\n  coalesce((\n    SELECT max(c) FROM (\n      SELECT count(*)::int AS c FROM pg_stat_activity\n      WHERE pid <> pg_backend_pid()\n        AND datname = current_database()\n        AND state = 'active'\n        AND query <> ''\n      GROUP BY query\n    ) q\n  ), 0)::int AS max_same_query\nFROM pg_stat_activity\nWHERE pid <> pg_backend_pid()\n  AND datname = current_database()";
export declare function dbPressureWarnings(p: DbPressureCounters): string[];
export declare function probeDbPressure(exec: {
    execute: (sql: string) => Promise<unknown>;
}, options?: {
    trivialQueryMs?: number;
}): Promise<DbPressure>;