Better error if trying to run query during copy

Author: porsager

README.md

@@ -1331,6 +1331,11 @@ This error is thrown for any queries that were pending when the timeout to [`sql
 
 This error is thrown if the startup phase of the connection (tcp, protocol negotiation, and auth) took more than the default 30 seconds or what was specified using `connect_timeout` or `PGCONNECT_TIMEOUT`.
 
+##### COPY_IN_PROGRESS
+> You cannot execute queries during copy
+
+This error is thrown if trying to run a query during a copy operation (writable / readable).
+
 ## TypeScript support
 
 `postgres` has TypeScript support. You can pass a row list type for your queries in this way:

src/connection.js

@@ -154,7 +154,10 @@ function Connection(options, queues = {}, { onopen = noop, onend = noop, onclose
   function execute(q) {
     if (terminated)
       return queryError(q, Errors.connection('CONNECTION_DESTROYED', options))
-
+    
+    if (stream)
+      return queryError(q, Errors.generic('COPY_IN_PROGRESS', 'You cannot execute queries during copy'))
+    
     if (q.cancelled)
       return
 
@@ -849,6 +852,7 @@ function Connection(options, queues = {}, { onopen = noop, onend = noop, onclose
       final(callback) {
         socket.write(b().c().end())
         final = callback
+        stream = null
       }
     })
     query.resolve(stream)

tests/index.js

@@ -2614,3 +2614,16 @@ t('Ensure reserve on query throws proper error', async() => {
     'wat', x, reserved.release()
   ]
 })
+
+t('query during copy error', async() => {
+  const sql = postgres(options) // eslint-disable-line
+  await sql`create table test (id serial primary key, name text)`
+  const copy = await sql`copy test from stdin`.writable()
+  const error = await sql`select 1`.catch(e => e)
+  await copy.end()
+
+  return [
+    'COPY_IN_PROGRESS', error.code,
+    await sql`drop table test`
+  ]
+})