Skip to content

P
Postgres FD Implementation
Commit 226a1005 authored by Tom Lane's avatar Tom Lane
Browse files
Options

Code review for btree page split WAL reduction patch. Make it actually work 

(original code *always* created a full-page image for the left page, thus
leaving the intended savings unrealized), avoid risk of not having enough room
on the page during xlog restore, squeeze out another couple bytes in the xlog
record, clean up neglected comments.
parent f7424b0d
Expand all Hide whitespace changes
Inline Side-by-side
Showing with 167 additions and 127 deletions
src/backend/access/nbtree/nbtinsert.c
View file @ 226a1005
This diff is collapsed.
src/backend/access/nbtree/nbtxlog.c
View file @ 226a1005
......@@ -8,7 +8,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtxlog.c,v 1.42 2007/02/08 05:05:53 momjian Exp $
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtxlog.c,v 1.43 2007/04/11 20:47:38 tgl Exp $
*
*-------------------------------------------------------------------------
*/
......@@ -125,7 +125,8 @@ forget_matching_deletion(RelFileNode node, BlockNumber delblk)
* in correct itemno sequence, but physically the opposite order from the
* original, because we insert them in the opposite of itemno order. This
* does not matter in any current btree code, but it's something to keep an
* eye on. Is it worth changing just on general principles?
* eye on. Is it worth changing just on general principles? See also the
* notes in btree_xlog_split().
*/
static void
_bt_restore_page(Page page, char *from, int len)
......@@ -264,14 +265,12 @@ btree_xlog_split(bool onleft, bool isroot,
{
xl_btree_split *xlrec = (xl_btree_split *) XLogRecGetData(record);
Relation reln;
Buffer lbuf, rbuf;
Page lpage, rpage;
BTPageOpaque ropaque, lopaque;
Buffer rbuf;
Page rpage;
BTPageOpaque ropaque;
char *datapos;
int datalen;
bool bkp_left = record->xl_info & XLR_BKP_BLOCK_1;
bool bkp_nextsib = record->xl_info & XLR_BKP_BLOCK_2;
OffsetNumber newitemoff;
OffsetNumber newitemoff = 0;
Item newitem = NULL;
Size newitemsz = 0;
......@@ -283,6 +282,7 @@ btree_xlog_split(bool onleft, bool isroot,
/* Forget any split this insertion completes */
if (xlrec->level > 0)
{
/* we assume SizeOfBtreeSplit is at least 16-bit aligned */
BlockNumber downlink = BlockIdGetBlockNumber((BlockId) datapos);
datapos += sizeof(BlockIdData);
......@@ -291,19 +291,22 @@ btree_xlog_split(bool onleft, bool isroot,
forget_matching_split(xlrec->node, downlink, false);
}
/* Extract newitem and newitemoff */
if (!bkp_left && onleft)
/* Extract newitem and newitemoff, if present */
if (onleft && !(record->xl_info & XLR_BKP_BLOCK_1))
{
IndexTupleData itupdata;
/* Extract the offset of the new tuple and it's contents */
/* Extract the offset (still assuming 16-bit alignment) */
memcpy(&newitemoff, datapos, sizeof(OffsetNumber));
datapos += sizeof(OffsetNumber);
datalen -= sizeof(OffsetNumber);
/*
* We need to copy the tuple header to apply IndexTupleDSize, because
* of alignment considerations. However, we assume that PageAddItem
* doesn't care about the alignment of the newitem pointer it's given.
*/
newitem = datapos;
/* Need to copy tuple header due to alignment considerations */
memcpy(&itupdata, datapos, sizeof(IndexTupleData));
newitemsz = IndexTupleDSize(itupdata);
newitemsz = MAXALIGN(newitemsz);
......@@ -311,7 +314,7 @@ btree_xlog_split(bool onleft, bool isroot,
datalen -= newitemsz;
}
/* Reconstruct right (new) sibling */
/* Reconstruct right (new) sibling from scratch */
rbuf = XLogReadBuffer(reln, xlrec->rightsib, true);
Assert(BufferIsValid(rbuf));
rpage = (Page) BufferGetPage(rbuf);
......@@ -331,57 +334,71 @@ btree_xlog_split(bool onleft, bool isroot,
PageSetTLI(rpage, ThisTimeLineID);
MarkBufferDirty(rbuf);
/* don't release the buffer yet, because reconstructing the left sibling
* needs to access the data on the right page
*/
/* Reconstruct left (original) sibling */
/* don't release the buffer yet; we touch right page's first item below */
if(!bkp_left)
/*
* Reconstruct left (original) sibling if needed. Note that this code
* ensures that the items remaining on the left page are in the correct
* item number order, but it does not reproduce the physical order they
* would have had. Is this worth changing? See also _bt_restore_page().
*/
if (!(record->xl_info & XLR_BKP_BLOCK_1))
{
lbuf = XLogReadBuffer(reln, xlrec->leftsib, false);
Buffer lbuf = XLogReadBuffer(reln, xlrec->leftsib, false);
if (BufferIsValid(lbuf))
{
lpage = (Page) BufferGetPage(lbuf);
lopaque = (BTPageOpaque) PageGetSpecialPointer(lpage);
Page lpage = (Page) BufferGetPage(lbuf);
BTPageOpaque lopaque = (BTPageOpaque) PageGetSpecialPointer(lpage);
if (!XLByteLE(lsn, PageGetLSN(lpage)))
{
/* Remove the items from the left page that were copied to
* right page, and add the new item if it was inserted to
* left page.
*/
OffsetNumber off;
OffsetNumber maxoff = PageGetMaxOffsetNumber(lpage);
OffsetNumber deletable[MaxOffsetNumber];
int ndeletable = 0;
ItemId hiItemId;
Item hiItem;
for(off = maxoff ; off >= xlrec->firstright; off--)
PageIndexTupleDelete(lpage, off);
/*
* Remove the items from the left page that were copied to
* the right page. Also remove the old high key, if any.
* (We must remove everything before trying to insert any
* items, else we risk not having enough space.)
*/
if (!P_RIGHTMOST(lopaque))
{
deletable[ndeletable++] = P_HIKEY;
/*
* newitemoff is given to us relative to the original
* page's item numbering, so adjust it for this deletion.
*/
newitemoff--;
}
for (off = xlrec->firstright; off <= maxoff; off++)
deletable[ndeletable++] = off;
if (ndeletable > 0)
PageIndexMultiDelete(lpage, deletable, ndeletable);
/*
* Add the new item if it was inserted on left page.
*/
if (onleft)
{
if (PageAddItem(lpage, newitem, newitemsz, newitemoff,
if (PageAddItem(lpage, newitem, newitemsz, newitemoff,
LP_USED) == InvalidOffsetNumber)
elog(PANIC, "can't add new item to left sibling after split");
elog(PANIC, "failed to add new item to left page after split");
}
/* Set high key equal to the first key on the right page */
hiItemId = PageGetItemId(rpage, P_FIRSTDATAKEY(ropaque));
hiItem = PageGetItem(rpage, hiItemId);
if(!P_RIGHTMOST(lopaque))
{
/* but remove the old high key first */
PageIndexTupleDelete(lpage, P_HIKEY);
}
if(PageAddItem(lpage, hiItem, ItemIdGetLength(hiItemId),
P_HIKEY, LP_USED) == InvalidOffsetNumber)
elog(PANIC, "can't add high key after split to left page");
if (PageAddItem(lpage, hiItem, ItemIdGetLength(hiItemId),
P_HIKEY, LP_USED) == InvalidOffsetNumber)
elog(PANIC, "failed to add high key to left page after split");
/* Fix opaque fields */
/* Fix opaque fields */
lopaque->btpo_flags = (xlrec->level == 0) ? BTP_LEAF : 0;
lopaque->btpo_next = xlrec->rightsib;
lopaque->btpo_cycleid = 0;
......@@ -393,16 +410,16 @@ btree_xlog_split(bool onleft, bool isroot,
UnlockReleaseBuffer(lbuf);
}
}
/* we no longer need the right buffer. */
/* We no longer need the right buffer */
UnlockReleaseBuffer(rbuf);
/* Fix left-link of the page to the right of the new right sibling */
if (!bkp_nextsib && xlrec->rnext != P_NONE)
if (xlrec->rnext != P_NONE && !(record->xl_info & XLR_BKP_BLOCK_2))
{
Buffer buffer = XLogReadBuffer(reln, xlrec->rnext, false);
if (BufferIsValid(buffer))
{
Page page = (Page) BufferGetPage(buffer);
......@@ -410,6 +427,7 @@ btree_xlog_split(bool onleft, bool isroot,
if (!XLByteLE(lsn, PageGetLSN(page)))
{
BTPageOpaque pageop = (BTPageOpaque) PageGetSpecialPointer(page);
pageop->btpo_prev = xlrec->rightsib;
PageSetLSN(page, lsn);
......@@ -770,48 +788,48 @@ btree_desc(StringInfo buf, uint8 xl_info, char *rec)
{
xl_btree_split *xlrec = (xl_btree_split *) rec;
appendStringInfo(buf, "split_l: rel %u/%u/%u ",
appendStringInfo(buf, "split_l: rel %u/%u/%u ",
xlrec->node.spcNode, xlrec->node.dbNode,
xlrec->node.relNode);
appendStringInfo(buf, "left %u, right %u off %u level %u",
xlrec->leftsib, xlrec->rightsib,
xlrec->firstright, xlrec->level);
appendStringInfo(buf, "left %u, right %u, next %u, level %u, firstright %d",
xlrec->leftsib, xlrec->rightsib, xlrec->rnext,
xlrec->level, xlrec->firstright);
break;
}
case XLOG_BTREE_SPLIT_R:
{
xl_btree_split *xlrec = (xl_btree_split *) rec;
appendStringInfo(buf, "split_r: rel %u/%u/%u ",
appendStringInfo(buf, "split_r: rel %u/%u/%u ",
xlrec->node.spcNode, xlrec->node.dbNode,
xlrec->node.relNode);
appendStringInfo(buf, "left %u, right %u off %u level %u",
xlrec->leftsib, xlrec->rightsib,
xlrec->firstright, xlrec->level);
appendStringInfo(buf, "left %u, right %u, next %u, level %u, firstright %d",
xlrec->leftsib, xlrec->rightsib, xlrec->rnext,
xlrec->level, xlrec->firstright);
break;
}
case XLOG_BTREE_SPLIT_L_ROOT:
{
xl_btree_split *xlrec = (xl_btree_split *) rec;
appendStringInfo(buf, "split_l_root: rel %u/%u/%u ",
appendStringInfo(buf, "split_l_root: rel %u/%u/%u ",
xlrec->node.spcNode, xlrec->node.dbNode,
xlrec->node.relNode);
appendStringInfo(buf, "left %u, right %u off %u level %u",
xlrec->leftsib, xlrec->rightsib,
xlrec->firstright, xlrec->level);
appendStringInfo(buf, "left %u, right %u, next %u, level %u, firstright %d",
xlrec->leftsib, xlrec->rightsib, xlrec->rnext,
xlrec->level, xlrec->firstright);
break;
}
case XLOG_BTREE_SPLIT_R_ROOT:
{
xl_btree_split *xlrec = (xl_btree_split *) rec;
appendStringInfo(buf, "split_r_root: rel %u/%u/%u ",
appendStringInfo(buf, "split_r_root: rel %u/%u/%u ",
xlrec->node.spcNode, xlrec->node.dbNode,
xlrec->node.relNode);
appendStringInfo(buf, "left %u, right %u off %u level %u",
xlrec->leftsib, xlrec->rightsib,
xlrec->firstright, xlrec->level);
appendStringInfo(buf, "left %u, right %u, next %u, level %u, firstright %d",
xlrec->leftsib, xlrec->rightsib, xlrec->rnext,
xlrec->level, xlrec->firstright);
break;
}
case XLOG_BTREE_DELETE:
......
src/include/access/nbtree.h
View file @ 226a1005
......@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/nbtree.h,v 1.112 2007/04/09 22:04:08 tgl Exp $
* $PostgreSQL: pgsql/src/include/access/nbtree.h,v 1.113 2007/04/11 20:47:38 tgl Exp $
*
*-------------------------------------------------------------------------
*/
......@@ -260,17 +260,17 @@ typedef struct xl_btree_insert
#define SizeOfBtreeInsert (offsetof(xl_btreetid, tid) + SizeOfIptrData)
/*
* On insert with split we save items of both left and right siblings
* and restore content of both pages from log record. This way takes less
* xlog space than the normal approach, because if we did it standardly,
* On insert with split, we save all the items going into the right sibling
* so that we can restore it completely from the log record. This way takes
* less xlog space than the normal approach, because if we did it standardly,
* XLogInsert would almost always think the right page is new and store its
* whole page image.
* whole page image. The left page, however, is handled in the normal
* incremental-update fashion.
*
* Note: the four XLOG_BTREE_SPLIT xl_info codes all use this data record.
* The _L and _R variants indicate whether the inserted tuple went into the
* left or right split page (and thus, whether newitemoff and the new item
* are stored or not.
* page of the split pair). The _ROOT variants indicate that we are splitting
* are stored or not). The _ROOT variants indicate that we are splitting
* the root page, and thus that a newroot record rather than an insert or
* split record should follow. Note that a split record never carries a
* metapage update --- we'll do that in the parent-level update.
......@@ -278,20 +278,25 @@ typedef struct xl_btree_insert
typedef struct xl_btree_split
{
RelFileNode node;
BlockNumber leftsib; /* orig page / new left page */
BlockNumber rightsib; /* new right page */
OffsetNumber firstright; /* first item stored on right page */
BlockNumber rnext; /* next/right block pointer */
uint32 level; /* tree level of page being split */
/* BlockIdData downlink follows if level > 0 */
/* OffsetNumber newitemoff follows in the _L variants. */
/* New item follows in the _L variants */
/* RIGHT PAGES TUPLES FOLLOW AT THE END */
BlockNumber leftsib; /* orig page / new left page */
BlockNumber rightsib; /* new right page */
BlockNumber rnext; /* next block (orig page's rightlink) */
uint32 level; /* tree level of page being split */
OffsetNumber firstright; /* first item moved to right page */
/*
* If level > 0, BlockIdData downlink follows. (We use BlockIdData
* rather than BlockNumber for alignment reasons: SizeOfBtreeSplit
* is only 16-bit aligned.)
*
* In the _L variants, next are OffsetNumber newitemoff and the new item.
* (In the _R variants, the new item is one of the right page's tuples.)
*
* Last are the right page's tuples in the form used by _bt_restore_page.
*/
} xl_btree_split;
#define SizeOfBtreeSplit (offsetof(xl_btree_split, level) + sizeof(uint32))
#define SizeOfBtreeSplit (offsetof(xl_btree_split, firstright) + sizeof(OffsetNumber))
/*
* This is what we need to know about delete of individual leaf index tuples.
......
src/include/catalog/catversion.h
View file @ 226a1005
......@@ -37,7 +37,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.402 2007/04/09 22:04:08 tgl Exp $
* $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.403 2007/04/11 20:47:38 tgl Exp $
*
*-------------------------------------------------------------------------
*/
......@@ -53,6 +53,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 200704091
#define CATALOG_VERSION_NO 200704111
#endif
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment