Tolerate concurrent stats index creation

Proof: observed the deployed stats fix restart app pods once when concurrent startup index creation hit PostgreSQL pg_class_relname_nsp_index; added an idempotent schema-index helper that treats concurrent already-created index errors as success and added regression tests for the exact duplicate-index race and unrelated duplicate errors. Revalidated targeted stats/schema tests, full npm test, and operator dashboard bundle build.

Assumptions: PostgreSQL error 23505 on pg_class_relname_nsp_index and 42P07 during CREATE INDEX IF NOT EXISTS mean another repo-owned process created the same schema object concurrently, so continuing is equivalent to the intended idempotent schema state.

Still fake: this does not remove already-written duplicate statistic rows with malformed historical stat_id strings; the loader de-dupes them at read time, and venue-native settlement truth remains limited to existing durable evidence.

src/lib/postgres.mjs

@@ -440,7 +440,7 @@ export async function ensureQuoteLifecycleRetentionSchema(pool) {
     CREATE INDEX IF NOT EXISTS ${QUOTE_LIFECYCLE_STATISTIC_SUBJECTS_TABLE}_bucket_idx
     ON ${QUOTE_LIFECYCLE_STATISTIC_SUBJECTS_TABLE} (bucket, latest_stage_at DESC NULLS LAST)
   `);
-  await pool.query(`
+  await ensureSchemaIndex(pool, `
     CREATE INDEX IF NOT EXISTS ${QUOTE_LIFECYCLE_STATISTIC_SUBJECTS_TABLE}_updated_idx
     ON ${QUOTE_LIFECYCLE_STATISTIC_SUBJECTS_TABLE} (updated_at DESC)
   `);
@@ -6418,8 +6418,25 @@ function withDepositCreatedAt(payload, effectiveAt) {
 }
 
 async function ensureExpressionIndex(pool, { name, table, expression }) {
-  await pool.query(`
+  await ensureSchemaIndex(pool, `
     CREATE INDEX IF NOT EXISTS ${name}
     ON ${table} (${expression})
   `);
 }
+
+export async function ensureSchemaIndex(pool, sql) {
+  try {
+    await pool.query(sql);
+  } catch (error) {
+    if (isConcurrentSchemaIndexExistsError(error)) return;
+    throw error;
+  }
+}
+
+function isConcurrentSchemaIndexExistsError(error) {
+  return error?.code === '42P07'
+    || (
+      error?.code === '23505'
+      && error?.constraint === 'pg_class_relname_nsp_index'
+    );
+}

test/postgres-quote-lifecycle-statistics.test.mjs

@@ -5,6 +5,7 @@ import {
   buildQuoteLifecycleStatistics,
 } from '../src/core/quote-lifecycle-statistics.mjs';
 import {
+  ensureSchemaIndex,
   loadQuoteLifecycleStatistics,
   refreshQuoteLifecycleStatistics,
 } from '../src/lib/postgres.mjs';
@@ -192,3 +193,35 @@ test('postgres quote lifecycle statistics loader returns all-time and clamped gr
   assert.match(issuedSql, /PARTITION BY grain, window_start, window_end/);
   assert.match(issuedSql, /duplicate_rank = 1/);
 });
+
+test('postgres schema index creation tolerates concurrent already-created index race', async () => {
+  let queryCount = 0;
+  const pool = {
+    async query() {
+      queryCount += 1;
+      const error = new Error('duplicate key value violates unique constraint "pg_class_relname_nsp_index"');
+      error.code = '23505';
+      error.constraint = 'pg_class_relname_nsp_index';
+      throw error;
+    },
+  };
+
+  await ensureSchemaIndex(pool, 'CREATE INDEX IF NOT EXISTS quote_lifecycle_stat_subjects_updated_idx ON quote_lifecycle_stat_subjects (updated_at DESC)');
+  assert.equal(queryCount, 1);
+});
+
+test('postgres schema index creation still rejects unrelated duplicate errors', async () => {
+  const pool = {
+    async query() {
+      const error = new Error('duplicate key value violates unrelated constraint');
+      error.code = '23505';
+      error.constraint = 'other_unique_constraint';
+      throw error;
+    },
+  };
+
+  await assert.rejects(
+    () => ensureSchemaIndex(pool, 'CREATE INDEX IF NOT EXISTS unrelated_idx ON some_table (id)'),
+    /unrelated constraint/,
+  );
+});