Postgres95 1.01 Distribution - Virgin SourcesPG95-1_01

1 files changed, 239 insertions, 0 deletions

diff --git a/src/backend/access/hash/hashinsert.c b/src/backend/access/hash/hashinsert.c
new file mode 100644
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+++ b/src/backend/access/hash/hashinsert.c
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+/*-------------------------------------------------------------------------
+ *
+ * hashinsert.c--
+ *    Item insertion in hash tables for Postgres.
+ *
+ * Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *    $Header: /cvsroot/pgsql/src/backend/access/hash/hashinsert.c,v 1.1.1.1 1996/07/09 06:21:10 scrappy Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "storage/bufmgr.h"
+#include "storage/bufpage.h"
+
+#include "utils/elog.h"
+#include "utils/palloc.h"
+#include "utils/rel.h"
+#include "utils/excid.h"
+
+#include "access/heapam.h"
+#include "access/genam.h"
+#include "access/hash.h"
+
+static InsertIndexResult _hash_insertonpg(Relation rel, Buffer buf, int keysz, ScanKey scankey, HashItem hitem, Buffer metabuf);
+static OffsetNumber _hash_pgaddtup(Relation rel, Buffer buf, int keysz, ScanKey itup_scankey, Size itemsize, HashItem hitem);
+
+/*
+ *  _hash_doinsert() -- Handle insertion of a single HashItem in the table.
+ *
+ *	This routine is called by the public interface routines, hashbuild
+ *	and hashinsert.  By here, hashitem is filled in, and has a unique
+ *	(xid, seqno) pair. The datum to be used as a "key" is in the
+ * 	hashitem. 
+ */
+InsertIndexResult
+_hash_doinsert(Relation rel, HashItem hitem)
+{
+    Buffer buf;
+    Buffer metabuf;
+    BlockNumber blkno;
+    HashMetaPage metap;
+    IndexTuple itup;
+    InsertIndexResult res;
+    ScanKey itup_scankey;
+    int natts;
+    Page page;
+    
+    metabuf = _hash_getbuf(rel, HASH_METAPAGE, HASH_READ);
+    metap = (HashMetaPage) BufferGetPage(metabuf);
+    _hash_checkpage((Page) metap, LH_META_PAGE);
+    
+    /* we need a scan key to do our search, so build one */
+    itup = &(hitem->hash_itup);
+    if ((natts = rel->rd_rel->relnatts) != 1)
+	elog(WARN, "Hash indices valid for only one index key.");
+    itup_scankey = _hash_mkscankey(rel, itup, metap);
+    
+    /* 
+     * find the first page in the bucket chain containing this key and
+     * place it in buf.  _hash_search obtains a read lock for us.
+     */
+    _hash_search(rel, natts, itup_scankey, &buf, metap);
+    page = BufferGetPage(buf);
+    _hash_checkpage(page, LH_BUCKET_PAGE);
+
+    /*
+     * trade in our read lock for a write lock so that we can do the
+     * insertion.
+     */
+    blkno = BufferGetBlockNumber(buf);
+    _hash_relbuf(rel, buf, HASH_READ);
+    buf = _hash_getbuf(rel, blkno, HASH_WRITE);
+    
+    
+    /*
+     * XXX btree comment (haven't decided what to do in hash): don't
+     * think the bucket can be split while we're reading the metapage.
+     *
+     * If the page was split between the time that we surrendered our
+     * read lock and acquired our write lock, then this page may no
+     * longer be the right place for the key we want to insert.
+     */
+    
+    /* do the insertion */
+    res = _hash_insertonpg(rel, buf, natts, itup_scankey,
+			   hitem, metabuf);
+    
+    /* be tidy */
+    _hash_freeskey(itup_scankey);
+    
+    return (res);
+}
+
+/*
+ *  _hash_insertonpg() -- Insert a tuple on a particular page in the table.
+ *
+ *	This recursive procedure does the following things:
+ *
+ *	    +  if necessary, splits the target page.  
+ *	    +  inserts the tuple.
+ *
+ *	On entry, we must have the right buffer on which to do the
+ *	insertion, and the buffer must be pinned and locked.  On return,
+ *	we will have dropped both the pin and the write lock on the buffer.
+ *
+ */
+static InsertIndexResult
+_hash_insertonpg(Relation rel,
+		 Buffer buf,
+		 int keysz,
+		 ScanKey scankey,
+		 HashItem hitem,
+		 Buffer metabuf)
+{
+    InsertIndexResult res; 
+    Page page;
+    BlockNumber itup_blkno;
+    OffsetNumber itup_off;
+    int itemsz;
+    HashPageOpaque pageopaque;
+    bool do_expand = false;	 
+    Buffer ovflbuf;
+    HashMetaPage metap;
+    Bucket bucket;
+    
+    metap = (HashMetaPage) BufferGetPage(metabuf);
+    _hash_checkpage((Page) metap, LH_META_PAGE);
+    
+    page = BufferGetPage(buf);
+    _hash_checkpage(page, LH_BUCKET_PAGE|LH_OVERFLOW_PAGE);
+    pageopaque = (HashPageOpaque) PageGetSpecialPointer(page);
+    bucket = pageopaque->hasho_bucket;
+
+    itemsz = IndexTupleDSize(hitem->hash_itup)
+	+ (sizeof(HashItemData) - sizeof(IndexTupleData));
+    itemsz = DOUBLEALIGN(itemsz);
+    
+    while (PageGetFreeSpace(page) < itemsz) {
+	/* 
+         * no space on this page; check for an overflow page 
+	 */
+	if (BlockNumberIsValid(pageopaque->hasho_nextblkno)) {
+	    /* 
+	     * ovfl page exists; go get it.  if it doesn't have room,
+	     * we'll find out next pass through the loop test above.
+	     */
+	    ovflbuf = _hash_getbuf(rel, pageopaque->hasho_nextblkno,
+				   HASH_WRITE);
+	    _hash_relbuf(rel, buf, HASH_WRITE);
+	    buf = ovflbuf;
+	    page = BufferGetPage(buf);
+	} else {
+	    /* 
+	     * we're at the end of the bucket chain and we haven't
+	     * found a page with enough room.  allocate a new overflow
+	     * page.
+	     */
+	    do_expand = true;
+	    ovflbuf = _hash_addovflpage(rel, &metabuf, buf);
+	    _hash_relbuf(rel, buf, HASH_WRITE);
+	    buf = ovflbuf;
+	    page = BufferGetPage(buf);
+
+	    if (PageGetFreeSpace(page) < itemsz) {
+		/* it doesn't fit on an empty page -- give up */
+		elog(WARN, "hash item too large");
+	    }
+	}
+	_hash_checkpage(page, LH_OVERFLOW_PAGE);
+	pageopaque = (HashPageOpaque) PageGetSpecialPointer(page);
+	Assert(pageopaque->hasho_bucket == bucket);
+    }
+
+    itup_off = _hash_pgaddtup(rel, buf, keysz, scankey, itemsz, hitem);
+    itup_blkno = BufferGetBlockNumber(buf);
+    
+    /* by here, the new tuple is inserted */
+    res = (InsertIndexResult) palloc(sizeof(InsertIndexResultData));
+    
+    ItemPointerSet(&(res->pointerData), itup_blkno, itup_off);
+    
+    if (res != NULL) {
+	/* 
+	 * Increment the number of keys in the table.
+	 * We switch lock access type just for a moment
+	 * to allow greater accessibility to the metapage. 
+	 */
+	metap = (HashMetaPage) _hash_chgbufaccess(rel, &metabuf,
+						  HASH_READ, HASH_WRITE);
+	metap->hashm_nkeys += 1;
+	metap = (HashMetaPage) _hash_chgbufaccess(rel, &metabuf,
+						  HASH_WRITE, HASH_READ);
+	
+    }
+    
+    _hash_wrtbuf(rel, buf);
+    
+    if (do_expand || 
+	(metap->hashm_nkeys / (metap->hashm_maxbucket + 1))
+	> metap->hashm_ffactor) {
+	_hash_expandtable(rel, metabuf);
+    }
+    _hash_relbuf(rel, metabuf, HASH_READ);
+    return (res);
+}	
+
+/*
+ *  _hash_pgaddtup() -- add a tuple to a particular page in the index.
+ *
+ *	This routine adds the tuple to the page as requested, and keeps the
+ *	write lock and reference associated with the page's buffer.  It is
+ *	an error to call pgaddtup() without a write lock and reference.
+ */
+static OffsetNumber
+_hash_pgaddtup(Relation rel,
+	       Buffer buf,
+	       int keysz,
+	       ScanKey itup_scankey,
+	       Size itemsize,
+	       HashItem hitem)
+{
+    OffsetNumber itup_off;
+    Page page;
+    
+    page = BufferGetPage(buf);
+    _hash_checkpage(page, LH_BUCKET_PAGE|LH_OVERFLOW_PAGE);
+
+    itup_off = OffsetNumberNext(PageGetMaxOffsetNumber(page));
+    (void) PageAddItem(page, (Item) hitem, itemsize, itup_off, LP_USED);
+    
+    /* write the buffer, but hold our lock */
+    _hash_wrtnorelbuf(rel, buf);
+    
+    return (itup_off);
+}