Fix some typos

Author: Yongtao Huang
Discussion: https://postgr.es/m/CAOe1Go1F99o5JsphtXdDC5bxm7AzetU8q3AxLh4AAVGKu1AzEQ@mail.gmail.com

src/backend/access/index/indexam.c

@@ -142,7 +142,7 @@ index_open(Oid relationId, LOCKMODE lockmode)
 }
 
 /* ----------------
- *		try_index_open - open a index relation by relation OID
+ *		try_index_open - open an index relation by relation OID
  *
  *		Same as index_open, except return NULL instead of failing
  *		if the relation does not exist.

src/backend/commands/explain.c

@@ -2395,7 +2395,7 @@ show_sort_keys(SortState *sortstate, List *ancestors, ExplainState *es)
 }
 
 /*
- * Show the sort keys for a IncrementalSort node.
+ * Show the sort keys for an IncrementalSort node.
  */
 static void
 show_incremental_sort_keys(IncrementalSortState *incrsortstate,

src/backend/replication/logical/worker.c

@@ -332,7 +332,7 @@ static TransactionId stream_xid = InvalidTransactionId;
  */
 static uint32 parallel_stream_nchanges = 0;
 
-/* Are we initializing a apply worker? */
+/* Are we initializing an apply worker? */
 bool		InitializingApplyWorker = false;
 
 /*

src/backend/utils/activity/wait_event.c

@@ -49,7 +49,7 @@ uint32	   *my_wait_event_info = &local_my_wait_event_info;
  * Hash tables for storing custom wait event ids and their names in
  * shared memory.
  *
- * WaitEventExtensionHashById is used to find the name from a event id.
+ * WaitEventExtensionHashById is used to find the name from an event id.
  * Any backend can search it to find custom wait events.
  *
  * WaitEventExtensionHashByName is used to find the event ID from a name.

src/test/modules/test_ginpostinglist/expected/test_ginpostinglist.out

@@ -1,7 +1,7 @@
 CREATE EXTENSION test_ginpostinglist;
 --
 -- All the logic is in the test_ginpostinglist() function. It will throw
--- a error if something fails.
+-- an error if something fails.
 --
 SELECT test_ginpostinglist();
 NOTICE:  testing with (0, 1), (0, 2), max 14 bytes

src/test/modules/test_ginpostinglist/sql/test_ginpostinglist.sql

@@ -2,6 +2,6 @@ CREATE EXTENSION test_ginpostinglist;
 
 --
 -- All the logic is in the test_ginpostinglist() function. It will throw
--- a error if something fails.
+-- an error if something fails.
 --
 SELECT test_ginpostinglist();