Fix typos and duplicate words

This fixes various typos, duplicated words, and tiny bits of whitespace
mainly in code comments but also in docs.

Author: Daniel Gustafsson <daniel@yesql.se>
Author: Heikki Linnakangas <hlinnaka@iki.fi>
Author: Alexander Lakhin <exclusion@gmail.com>
Author: David Rowley <dgrowleyml@gmail.com>
Author: Nazir Bilal Yavuz <byavuz81@gmail.com>
Discussion: https://postgr.es/m/3F577953-A29E-4722-98AD-2DA9EFF2CBB8@yesql.se

src/backend/access/gin/ginbtree.c

@@ -766,7 +766,7 @@ ginFinishSplit(GinBtree btree, GinBtreeStack *stack, bool freestack,
 /*
  * An entry point to ginFinishSplit() that is used when we stumble upon an
  * existing incompletely split page in the tree, as opposed to completing a
- * split that we just made outselves. The difference is that stack->buffer may
+ * split that we just made ourselves. The difference is that stack->buffer may
  * be merely share-locked on entry, and will be upgraded to exclusive mode.
  *
  * Note: Upgrading the lock momentarily releases it. Doing that in a scan

src/backend/access/heap/pruneheap.c

@@ -33,7 +33,7 @@
 typedef struct
 {
 	/*-------------------------------------------------------
-	 * Arguments passed to heap_page_and_freeze()
+	 * Arguments passed to heap_page_prune_and_freeze()
 	 *-------------------------------------------------------
 	 */
 
@@ -306,7 +306,7 @@ heap_page_prune_opt(Relation relation, Buffer buffer)
  * If the HEAP_PRUNE_FREEZE option is set, we will also freeze tuples if it's
  * required in order to advance relfrozenxid / relminmxid, or if it's
  * considered advantageous for overall system performance to do so now.  The
- * 'cutoffs', 'presult', 'new_refrozen_xid' and 'new_relmin_mxid' arguments
+ * 'cutoffs', 'presult', 'new_relfrozen_xid' and 'new_relmin_mxid' arguments
  * are required when freezing.  When HEAP_PRUNE_FREEZE option is set, we also
  * set presult->all_visible and presult->all_frozen on exit, to indicate if
  * the VM bits can be set.  They are always set to false when the
@@ -337,7 +337,7 @@ heap_page_prune_opt(Relation relation, Buffer buffer)
  * off_loc is the offset location required by the caller to use in error
  * callback.
  *
- * new_relfrozen_xid and new_relmin_xid must provided by the caller if the
+ * new_relfrozen_xid and new_relmin_mxid must provided by the caller if the
  * HEAP_PRUNE_FREEZE option is set.  On entry, they contain the oldest XID and
  * multi-XID seen on the relation so far.  They will be updated with oldest
  * values present on the page after pruning.  After processing the whole

src/backend/access/nbtree/nbtutils.c

@@ -1756,7 +1756,7 @@ _bt_start_prim_scan(IndexScanDesc scan, ScanDirection dir)
  *
  * (The rules are the same for backwards scans, except that the operators are
  * flipped: just replace the precondition's >= operator with a <=, and the
- * postcondition's <= operator with with a >=.  In other words, just swap the
+ * postcondition's <= operator with a >=.  In other words, just swap the
  * precondition with the postcondition.)
  *
  * We also deal with "advancing" non-required arrays here.  Callers whose
@@ -4133,7 +4133,7 @@ _bt_checkkeys_look_ahead(IndexScanDesc scan, BTReadPageState *pstate,
 	else
 	{
 		/*
-		 * Failure -- "ahead" tuple is too far ahead (we were too aggresive).
+		 * Failure -- "ahead" tuple is too far ahead (we were too aggressive).
 		 *
 		 * Reset the number of rechecks, and aggressively reduce the target
 		 * distance (we're much more aggressive here than we were when the

src/backend/access/rmgrdesc/xactdesc.c

@@ -25,7 +25,7 @@
  * Parse the WAL format of an xact commit and abort records into an easier to
  * understand format.
  *
- * This routines are in xactdesc.c because they're accessed in backend (when
+ * These routines are in xactdesc.c because they're accessed in backend (when
  * replaying WAL) and frontend (pg_waldump) code. This file is the only xact
  * specific one shared between both. They're complicated enough that
  * duplication would be bothersome.