Fix typos in comments

Dmitriy Olshevskiy

src/backend/access/gin/ginpostinglist.c

@@ -23,7 +23,7 @@
 /*
  * For encoding purposes, item pointers are represented as 64-bit unsigned
  * integers. The lowest 11 bits represent the offset number, and the next
- * lowest 32 bits are the block number. That leaves 17 bits unused, ie.
+ * lowest 32 bits are the block number. That leaves 17 bits unused, i.e.
  * only 43 low bits are used.
  *
  * These 43-bit integers are encoded using varbyte encoding. In each byte,
@@ -51,16 +51,16 @@
  * Removing number is actually replacement of two numbers with their sum. We
  * have to prove that varbyte encoding of a sum can't be longer than varbyte
  * encoding of its summands. Sum of two numbers is at most one bit wider than
- * than the larger of the summands. Widening a number by one bit enlarges its
- * length in varbyte encoding by at most one byte. Therefore, varbyte encoding
- * of sum is at most one byte longer than varbyte encoding of larger summand.
- * Lesser summand is at least one byte, so the sum cannot take more space than
- * the summands, Q.E.D.
+ * the larger of the summands. Widening a number by one bit enlarges its length
+ * in varbyte encoding by at most one byte. Therefore, varbyte encoding of sum
+ * is at most one byte longer than varbyte encoding of larger summand. Lesser
+ * summand is at least one byte, so the sum cannot take more space than the
+ * summands, Q.E.D.
  *
  * This property greatly simplifies VACUUM, which can assume that posting
  * lists always fit on the same page after vacuuming. Note that even though
  * that holds for removing items from a posting list, you must also be
- * careful to not cause expansion e.g when merging uncompressed items on the
+ * careful to not cause expansion e.g. when merging uncompressed items on the
  * page into the compressed lists, when vacuuming.
  */
 

src/backend/access/heap/heapam.c

@@ -7289,7 +7289,7 @@ ExtractReplicaIdentity(Relation relation, HeapTuple tp, bool key_changed, bool *
 		{
 			/*
 			 * The OID column can appear in an index definition, but that's
-			 * OK, becuse we always copy the OID if present (see below). Other
+			 * OK, because we always copy the OID if present (see below). Other
 			 * system columns may not.
 			 */
 			if (attno == ObjectIdAttributeNumber)

src/backend/access/nbtree/README

@@ -470,7 +470,7 @@ not be seen under normal circumstances; only if insertion to the parent
 has failed for some reason.
 
 We flag the left page, even though it's the right page that's missing the
-downlink, beacuse it's more convenient to know already when following the
+downlink, because it's more convenient to know already when following the
 right-link from the left page to the right page that it will need to have
 its downlink inserted to the parent.
 

src/backend/access/transam/xact.c

@@ -2005,7 +2005,7 @@ CommitTransaction(void)
 	if (!is_parallel_worker)
 	{
 		/*
-		 * We need to mark our XIDs as commited in pg_clog.  This is where we
+		 * We need to mark our XIDs as committed in pg_clog.  This is where we
 		 * durably commit.
 		 */
 		latestXid = RecordTransactionCommit();
@@ -2764,7 +2764,7 @@ CommitTransactionCommand(void)
 			/*
 			 * Here we are in the middle of a transaction block but one of the
 			 * commands caused an abort so we do nothing but remain in the
-			 * abort state.  Eventually we will get a ROLLBACK comand.
+			 * abort state.  Eventually we will get a ROLLBACK command.
 			 */
 		case TBLOCK_ABORT:
 		case TBLOCK_SUBABORT: