Improve code comments

petere · petere · commit 88c6cff8e71e · 2017-06-13T10:43:36.000-04:00
Author: Erik Rijkers &lt;er@xs4all.nl&gt;
diff --git a/src/backend/replication/logical/tablesync.c b/src/backend/replication/logical/tablesync.c
@@ -12,18 +12,18 @@
  *	  logical replication.
  *
  *	  The initial data synchronization is done separately for each table,
- *	  in separate apply worker that only fetches the initial snapshot data
- *	  from the publisher and then synchronizes the position in stream with
+ *	  in a separate apply worker that only fetches the initial snapshot data
+ *	  from the publisher and then synchronizes the position in the stream with
  *	  the main apply worker.
  *
- *	  The are several reasons for doing the synchronization this way:
+ *	  There are several reasons for doing the synchronization this way:
  *	   - It allows us to parallelize the initial data synchronization
  *		 which lowers the time needed for it to happen.
  *	   - The initial synchronization does not have to hold the xid and LSN
  *		 for the time it takes to copy data of all tables, causing less
  *		 bloat and lower disk consumption compared to doing the
- *		 synchronization in single process for whole database.
- *	   - It allows us to synchronize the tables added after the initial
+ *		 synchronization in a single process for the whole database.
+ *	   - It allows us to synchronize any tables added after the initial
  *		 synchronization has finished.
  *
  *	  The stream position synchronization works in multiple steps.
@@ -147,7 +147,7 @@ finish_sync_worker(void)
 }
 
 /*
- * Wait until the relation synchronization state is set in catalog to the
+ * Wait until the relation synchronization state is set in the catalog to the
  * expected one.
  *
  * Used when transitioning from CATCHUP state to SYNCDONE.
@@ -206,12 +206,12 @@ wait_for_relation_state_change(Oid relid, char expected_state)
 }
 
 /*
- * Wait until the the apply worker changes the state of our synchronization
+ * Wait until the apply worker changes the state of our synchronization
  * worker to the expected one.
  *
  * Used when transitioning from SYNCWAIT state to CATCHUP.
  *
- * Returns false if the apply worker has disappeared or table state has been
+ * Returns false if the apply worker has disappeared or the table state has been
  * reset.
  */
 static bool
@@ -225,7 +225,7 @@ wait_for_worker_state_change(char expected_state)
 
 		CHECK_FOR_INTERRUPTS();
 
-		/* Bail if he apply has died. */
+		/* Bail if the apply has died. */
 		LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
 		worker = logicalrep_worker_find(MyLogicalRepWorker->subid,
 										InvalidOid, false);
@@ -333,7 +333,7 @@ process_syncing_tables_for_apply(XLogRecPtr current_lsn)
 
 	Assert(!IsTransactionState());
 
-	/* We need up to date sync state info for subscription tables here. */
+	/* We need up-to-date sync state info for subscription tables here. */
 	if (!table_states_valid)
 	{
 		MemoryContext oldctx;
@@ -365,7 +365,7 @@ process_syncing_tables_for_apply(XLogRecPtr current_lsn)
 	}
 
 	/*
-	 * Prepare hash table for tracking last start times of workers, to avoid
+	 * Prepare a hash table for tracking last start times of workers, to avoid
 	 * immediate restarts.  We don't need it if there are no tables that need
 	 * syncing.
 	 */
@@ -401,7 +401,7 @@ process_syncing_tables_for_apply(XLogRecPtr current_lsn)
 		{
 			/*
 			 * Apply has caught up to the position where the table sync has
-			 * finished.  Time to mark the table as ready so that apply will
+			 * finished.  Mark the table as ready so that the apply will
 			 * just continue to replicate it normally.
 			 */
 			if (current_lsn >= rstate->lsn)
@@ -436,7 +436,7 @@ process_syncing_tables_for_apply(XLogRecPtr current_lsn)
 			else
 
 				/*
-				 * If no sync worker for this table yet, count running sync
+				 * If there is no sync worker for this table yet, count running sync
 				 * workers for this subscription, while we have the lock, for
 				 * later.
 				 */
@@ -477,7 +477,7 @@ process_syncing_tables_for_apply(XLogRecPtr current_lsn)
 
 			/*
 			 * If there is no sync worker registered for the table and there
-			 * is some free sync worker slot, start new sync worker for the
+			 * is some free sync worker slot, start a new sync worker for the
 			 * table.
 			 */
 			else if (!syncworker && nsyncworkers < max_sync_workers_per_subscription)
@@ -551,7 +551,7 @@ copy_read_data(void *outbuf, int minread, int maxread)
 	int			bytesread = 0;
 	int			avail;
 
-	/* If there are some leftover data from previous read, use them. */
+	/* If there are some leftover data from previous read, use it. */
 	avail = copybuf->len - copybuf->cursor;
 	if (avail)
 	{
@@ -694,7 +694,7 @@ fetch_remote_table_info(char *nspname, char *relname,
 				(errmsg("could not fetch table info for table \"%s.%s\": %s",
 						nspname, relname, res->err)));
 
-	/* We don't know number of rows coming, so allocate enough space. */
+	/* We don't know the number of rows coming, so allocate enough space. */
 	lrel->attnames = palloc0(MaxTupleAttributeNumber * sizeof(char *));
 	lrel->atttyps = palloc0(MaxTupleAttributeNumber * sizeof(Oid));
 	lrel->attkeys = NULL;
@@ -852,22 +852,22 @@ LogicalRepSyncTableStart(XLogRecPtr *origin_startpos)
 				pgstat_report_stat(false);
 
 				/*
-				 * We want to do the table data sync in single transaction.
+				 * We want to do the table data sync in a single transaction.
 				 */
 				StartTransactionCommand();
 
 				/*
-				 * Use standard write lock here. It might be better to
-				 * disallow access to table while it's being synchronized. But
+				 * Use a standard write lock here. It might be better to
+				 * disallow access to the table while it's being synchronized. But
 				 * we don't want to block the main apply process from working
-				 * and it has to open relation in RowExclusiveLock when
+				 * and it has to open the relation in RowExclusiveLock when
 				 * remapping remote relation id to local one.
 				 */
 				rel = heap_open(MyLogicalRepWorker->relid, RowExclusiveLock);
 
 				/*
-				 * Create temporary slot for the sync process. We do this
-				 * inside transaction so that we can use the snapshot made by
+				 * Create a temporary slot for the sync process. We do this
+				 * inside the transaction so that we can use the snapshot made by
 				 * the slot to get existing data.
 				 */
 				res = walrcv_exec(wrconn,
@@ -883,7 +883,7 @@ LogicalRepSyncTableStart(XLogRecPtr *origin_startpos)
 				 * Create new temporary logical decoding slot.
 				 *
 				 * We'll use slot for data copy so make sure the snapshot is
-				 * used for the transaction, that way the COPY will get data
+				 * used for the transaction; that way the COPY will get data
 				 * that is consistent with the lsn used by the slot to start
 				 * decoding.
 				 */
