fix: sync rows query after error

packages/pg/lib/query.js

@@ -120,7 +120,12 @@ class Query extends EventEmitter {
   }
 
   handleError(err, connection) {
-    // need to sync after error during a prepared statement
+    // rows-mode uses Flush instead of pipelining Sync in _getRows. After an
+    // ErrorResponse the backend ignores messages until Sync, so send one here
+    // to ensure ReadyForQuery arrives and the client can process later queries.
+    if (this.rows) {
+      connection.sync()
+    }
     if (this._canceledDueToError) {
       err = this._canceledDueToError
       this._canceledDueToError = false

packages/pg/test/unit/client/query-error-sync-tests.js

@@ -0,0 +1,36 @@
+'use strict'
+const helper = require('./test-helper')
+const Query = require('../../../lib/query')
+const assert = require('assert')
+const suite = new helper.Suite()
+const test = suite.test.bind(suite)
+
+test('rows-mode query syncs after an error', function () {
+  let syncCalls = 0
+  const query = new Query({ text: 'select 1', rows: 2 }, function (err) {
+    assert.equal(err.message, 'boom')
+  })
+
+  query.handleError(new Error('boom'), {
+    sync: function () {
+      syncCalls++
+    },
+  })
+
+  assert.equal(syncCalls, 1)
+})
+
+test('normal query does not send an extra sync after an error', function () {
+  let syncCalls = 0
+  const query = new Query({ text: 'select 1' }, function (err) {
+    assert.equal(err.message, 'boom')
+  })
+
+  query.handleError(new Error('boom'), {
+    sync: function () {
+      syncCalls++
+    },
+  })
+
+  assert.equal(syncCalls, 0)
+})