0002-Remove-redundant-hash-function-_hash_step-and-do-som.patch

From ef4180ffcaea44054d5b4894240be804c3970c6d Mon Sep 17 00:00:00 2001
From: ashu <ashutosh12.1@example.com>
Date: Mon, 7 Aug 2017 16:22:19 +0530
Subject: [PATCH] Remove redundant hash function _hash_step and do some code
 cleanup.

Remove redundant function _hash_step() and some of the unused members
of HashScanOpaqueData. The function _hash_step() used to find the next
qualifing tuple in the index page is no more required as new hash index
works page at a time which means it reads all the qualifing tuples in a
page at once with the help of _hash_readpage().

Patch by Ashutosh Sharma <ashu.coek88@gmail.com>
---
 src/backend/access/hash/hashsearch.c | 206 -----------------------------------
 src/include/access/hash.h            |  15 ---
 2 files changed, 221 deletions(-)

diff --git a/src/backend/access/hash/hashsearch.c b/src/backend/access/hash/hashsearch.c
index f4408ab..58eb108 100644
--- a/src/backend/access/hash/hashsearch.c
+++ b/src/backend/access/hash/hashsearch.c
@@ -431,212 +431,6 @@ _hash_first(IndexScanDesc scan, ScanDirection dir)
 }
 
 /*
- *	_hash_step() -- step to the next valid item in a scan in the bucket.
- *
- *		If no valid record exists in the requested direction, return
- *		false.  Else, return true and set the hashso_curpos for the
- *		scan to the right thing.
- *
- *		Here we need to ensure that if the scan has started during split, then
- *		skip the tuples that are moved by split while scanning bucket being
- *		populated and then scan the bucket being split to cover all such
- *		tuples.  This is done to ensure that we don't miss tuples in the scans
- *		that are started during split.
- *
- *		'bufP' points to the current buffer, which is pinned and read-locked.
- *		On success exit, we have pin and read-lock on whichever page
- *		contains the right item; on failure, we have released all buffers.
- */
-bool
-_hash_step(IndexScanDesc scan, Buffer *bufP, ScanDirection dir)
-{
-	Relation	rel = scan->indexRelation;
-	HashScanOpaque so = (HashScanOpaque) scan->opaque;
-	ItemPointer current;
-	Buffer		buf;
-	Page		page;
-	HashPageOpaque opaque;
-	OffsetNumber maxoff;
-	OffsetNumber offnum;
-	BlockNumber blkno;
-	IndexTuple	itup;
-
-	current = &(so->hashso_curpos);
-
-	buf = *bufP;
-	_hash_checkpage(rel, buf, LH_BUCKET_PAGE | LH_OVERFLOW_PAGE);
-	page = BufferGetPage(buf);
-	opaque = (HashPageOpaque) PageGetSpecialPointer(page);
-
-	/*
-	 * If _hash_step is called from _hash_first, current will not be valid, so
-	 * we can't dereference it.  However, in that case, we presumably want to
-	 * start at the beginning/end of the page...
-	 */
-	maxoff = PageGetMaxOffsetNumber(page);
-	if (ItemPointerIsValid(current))
-		offnum = ItemPointerGetOffsetNumber(current);
-	else
-		offnum = InvalidOffsetNumber;
-
-	/*
-	 * 'offnum' now points to the last tuple we examined (if any).
-	 *
-	 * continue to step through tuples until: 1) we get to the end of the
-	 * bucket chain or 2) we find a valid tuple.
-	 */
-	do
-	{
-		switch (dir)
-		{
-			case ForwardScanDirection:
-				if (offnum != InvalidOffsetNumber)
-					offnum = OffsetNumberNext(offnum);	/* move forward */
-				else
-				{
-					/* new page, locate starting position by binary search */
-					offnum = _hash_binsearch(page, so->hashso_sk_hash);
-				}
-
-				for (;;)
-				{
-					/*
-					 * check if we're still in the range of items with the
-					 * target hash key
-					 */
-					if (offnum <= maxoff)
-					{
-						Assert(offnum >= FirstOffsetNumber);
-						itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum));
-
-						/*
-						 * skip the tuples that are moved by split operation
-						 * for the scan that has started when split was in
-						 * progress
-						 */
-						if (so->hashso_buc_populated && !so->hashso_buc_split &&
-							(itup->t_info & INDEX_MOVED_BY_SPLIT_MASK))
-						{
-							offnum = OffsetNumberNext(offnum);	/* move forward */
-							continue;
-						}
-
-						if (so->hashso_sk_hash == _hash_get_indextuple_hashkey(itup))
-							break;	/* yes, so exit for-loop */
-					}
-
-					/* Before leaving current page, deal with any killed items */
-					if (so->numKilled > 0)
-						_hash_kill_items(scan);
-
-					/*
-					 * ran off the end of this page, try the next
-					 */
-					_hash_readnext(scan, &buf, &page, &opaque);
-					if (BufferIsValid(buf))
-					{
-						maxoff = PageGetMaxOffsetNumber(page);
-						offnum = _hash_binsearch(page, so->hashso_sk_hash);
-					}
-					else
-					{
-						itup = NULL;
-						break;	/* exit for-loop */
-					}
-				}
-				break;
-
-			case BackwardScanDirection:
-				if (offnum != InvalidOffsetNumber)
-					offnum = OffsetNumberPrev(offnum);	/* move back */
-				else
-				{
-					/* new page, locate starting position by binary search */
-					offnum = _hash_binsearch_last(page, so->hashso_sk_hash);
-				}
-
-				for (;;)
-				{
-					/*
-					 * check if we're still in the range of items with the
-					 * target hash key
-					 */
-					if (offnum >= FirstOffsetNumber)
-					{
-						Assert(offnum <= maxoff);
-						itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum));
-
-						/*
-						 * skip the tuples that are moved by split operation
-						 * for the scan that has started when split was in
-						 * progress
-						 */
-						if (so->hashso_buc_populated && !so->hashso_buc_split &&
-							(itup->t_info & INDEX_MOVED_BY_SPLIT_MASK))
-						{
-							offnum = OffsetNumberPrev(offnum);	/* move back */
-							continue;
-						}
-
-						if (so->hashso_sk_hash == _hash_get_indextuple_hashkey(itup))
-							break;	/* yes, so exit for-loop */
-					}
-
-					/* Before leaving current page, deal with any killed items */
-					if (so->numKilled > 0)
-						_hash_kill_items(scan);
-
-					/*
-					 * ran off the end of this page, try the next
-					 */
-					_hash_readprev(scan, &buf, &page, &opaque);
-					if (BufferIsValid(buf))
-					{
-						TestForOldSnapshot(scan->xs_snapshot, rel, page);
-						maxoff = PageGetMaxOffsetNumber(page);
-						offnum = _hash_binsearch_last(page, so->hashso_sk_hash);
-					}
-					else
-					{
-						itup = NULL;
-						break;	/* exit for-loop */
-					}
-				}
-				break;
-
-			default:
-				/* NoMovementScanDirection */
-				/* this should not be reached */
-				itup = NULL;
-				break;
-		}
-
-		if (itup == NULL)
-		{
-			/*
-			 * We ran off the end of the bucket without finding a match.
-			 * Release the pin on bucket buffers.  Normally, such pins are
-			 * released at end of scan, however scrolling cursors can
-			 * reacquire the bucket lock and pin in the same scan multiple
-			 * times.
-			 */
-			*bufP = so->hashso_curbuf = InvalidBuffer;
-			ItemPointerSetInvalid(current);
-			_hash_dropscanbuf(rel, so);
-			return false;
-		}
-
-		/* check the tuple quals, loop around if not met */
-	} while (!_hash_checkqual(scan, itup));
-
-	/* if we made it to here, we've found a valid tuple */
-	blkno = BufferGetBlockNumber(buf);
-	*bufP = so->hashso_curbuf = buf;
-	ItemPointerSet(current, blkno, offnum);
-	return true;
-}
-
-/*
  *	_hash_readpage() -- Load data from current index page into so->currPos
  *
  *	We scan all the items in the current index page and save them into
diff --git a/src/include/access/hash.h b/src/include/access/hash.h
index 3e90b89..19fb147 100644
--- a/src/include/access/hash.h
+++ b/src/include/access/hash.h
@@ -159,14 +159,6 @@ typedef struct HashScanOpaqueData
 	/* Hash value of the scan key, ie, the hash key we seek */
 	uint32		hashso_sk_hash;
 
-	/*
-	 * We also want to remember which buffer we're currently examining in the
-	 * scan. We keep the buffer pinned (but not locked) across hashgettuple
-	 * calls, in order to avoid doing a ReadBuffer() for every tuple in the
-	 * index.
-	 */
-	Buffer		hashso_curbuf;
-
 	/* remember the buffer associated with primary bucket */
 	Buffer		hashso_bucket_buf;
 
@@ -177,12 +169,6 @@ typedef struct HashScanOpaqueData
 	 */
 	Buffer		hashso_split_bucket_buf;
 
-	/* Current position of the scan, as an index TID */
-	ItemPointerData hashso_curpos;
-
-	/* Current position of the scan, as a heap TID */
-	ItemPointerData hashso_heappos;
-
 	/* Whether scan starts on bucket being populated due to split */
 	bool		hashso_buc_populated;
 
@@ -432,7 +418,6 @@ extern void _hash_finish_split(Relation rel, Buffer metabuf, Buffer obuf,
 /* hashsearch.c */
 extern bool _hash_next(IndexScanDesc scan, ScanDirection dir);
 extern bool _hash_first(IndexScanDesc scan, ScanDirection dir);
-extern bool _hash_step(IndexScanDesc scan, Buffer *bufP, ScanDirection dir);
 
 /* hashsort.c */
 typedef struct HSpool HSpool;	/* opaque struct in hashsort.c */
-- 
1.8.3.1