1 files changed, 382 insertions, 0 deletions
diff --git a/src/backend/access/gist/gistscan.c b/src/backend/access/gist/gistscan.c
new file mode 100644
index 00000000000..f09c52019b1
--- /dev/null
+++ b/src/backend/access/gist/gistscan.c
@@ -0,0 +1,382 @@
+/*-------------------------------------------------------------------------
+ *
+ * gistscan.c--
+ *    routines to manage scans on index relations
+ *
+ *
+ * IDENTIFICATION
+ *    /usr/local/devel/pglite/cvs/src/backend/access/gist/gistscan.c,v 1.7 1995/06/14 00:10:05 jolly Exp
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "c.h"
+#include "postgres.h"
+
+#include "storage/bufmgr.h"
+#include "storage/bufpage.h"
+
+#include "utils/elog.h"
+#include "utils/palloc.h"
+#include "utils/rel.h"
+
+#include "access/heapam.h"
+#include "access/genam.h"
+#include "access/gist.h"
+#include "access/giststrat.h"
+
+/* routines defined and used here */
+static void gistregscan(IndexScanDesc s);
+static void gistdropscan(IndexScanDesc s);
+static void gistadjone(IndexScanDesc s, int op, BlockNumber blkno,
+		     OffsetNumber offnum);
+static void adjuststack(GISTSTACK *stk, BlockNumber blkno,
+			OffsetNumber offnum);
+static void adjustiptr(IndexScanDesc s, ItemPointer iptr,
+		       int op, BlockNumber blkno, OffsetNumber offnum);
+
+/*
+ *  Whenever we start a GiST scan in a backend, we register it in private
+ *  space.  Then if the GiST index gets updated, we check all registered
+ *  scans and adjust them if the tuple they point at got moved by the
+ *  update.  We only need to do this in private space, because when we update
+ *  an GiST we have a write lock on the tree, so no other process can have
+ *  any locks at all on it.  A single transaction can have write and read
+ *  locks on the same object, so that's why we need to handle this case.
+ */
+
+typedef struct GISTScanListData {
+    IndexScanDesc		gsl_scan;
+    struct GISTScanListData	*gsl_next;
+} GISTScanListData;
+
+typedef GISTScanListData	*GISTScanList;
+
+/* pointer to list of local scans on GiSTs */
+static GISTScanList GISTScans = (GISTScanList) NULL;
+     
+IndexScanDesc
+gistbeginscan(Relation r,
+	    bool fromEnd,
+	    uint16 nkeys,
+	    ScanKey key)
+{
+    IndexScanDesc s;
+    
+    RelationSetLockForRead(r);
+    s = RelationGetIndexScan(r, fromEnd, nkeys, key);
+    gistregscan(s);
+    
+    return (s);
+}
+
+void
+gistrescan(IndexScanDesc s, bool fromEnd, ScanKey key)
+{
+    GISTScanOpaque p;
+    int i;
+    
+    if (!IndexScanIsValid(s)) {
+	elog(WARN, "gistrescan: invalid scan.");
+	return;
+    }
+    
+    /*
+     *  Clear all the pointers.
+     */
+    
+    ItemPointerSetInvalid(&s->previousItemData);
+    ItemPointerSetInvalid(&s->currentItemData);
+    ItemPointerSetInvalid(&s->nextItemData);
+    ItemPointerSetInvalid(&s->previousMarkData);
+    ItemPointerSetInvalid(&s->currentMarkData);
+    ItemPointerSetInvalid(&s->nextMarkData);
+    
+    /*
+     *  Set flags.
+     */
+    if (RelationGetNumberOfBlocks(s->relation) == 0) {
+	s->flags = ScanUnmarked;
+    } else if (fromEnd) {
+	s->flags = ScanUnmarked | ScanUncheckedPrevious;
+    } else {
+	s->flags = ScanUnmarked | ScanUncheckedNext;
+    }
+    
+    s->scanFromEnd = fromEnd;
+    
+    if (s->numberOfKeys > 0) {
+	memmove(s->keyData,
+		key,
+		s->numberOfKeys * sizeof(ScanKeyData));
+    }
+    
+    p = (GISTScanOpaque) s->opaque;
+    if (p != (GISTScanOpaque) NULL) {
+	freestack(p->s_stack);
+	freestack(p->s_markstk);
+	p->s_stack = p->s_markstk = (GISTSTACK *) NULL;
+	p->s_flags = 0x0;
+    } else {
+	/* initialize opaque data */
+	p = (GISTScanOpaque) palloc(sizeof(GISTScanOpaqueData));
+	p->s_stack = p->s_markstk = (GISTSTACK *) NULL;
+	p->s_flags = 0x0;
+	s->opaque = p;
+	p->giststate = (GISTSTATE *)palloc(sizeof(GISTSTATE));
+	initGISTstate(p->giststate, s->relation);
+	if (s->numberOfKeys > 0) 
+	  /* 
+	  ** Play games here with the scan key to use the Consistent
+	  ** function for all comparisons:
+	  ** 1) the sk_procedure field will now be used to hold the 
+	  **    strategy number
+	  ** 2) the sk_func field will point to the Consistent function 
+	  */
+	  for (i = 0; i < s->numberOfKeys; i++) {
+	    /* s->keyData[i].sk_procedure 
+		= index_getprocid(s->relation, 1, GIST_CONSISTENT_PROC); */
+	      s->keyData[i].sk_procedure 
+		= RelationGetGISTStrategy(s->relation, s->keyData[i].sk_attno, 
+					  s->keyData[i].sk_procedure);
+	      s->keyData[i].sk_func = p->giststate->consistentFn;
+	  }
+    }
+}
+
+void
+gistmarkpos(IndexScanDesc s)
+{
+    GISTScanOpaque p;
+    GISTSTACK *o, *n, *tmp;
+    
+    s->currentMarkData = s->currentItemData;
+    p = (GISTScanOpaque) s->opaque;
+    if (p->s_flags & GS_CURBEFORE)
+	p->s_flags |= GS_MRKBEFORE;
+    else
+	p->s_flags &= ~GS_MRKBEFORE;
+    
+    o = (GISTSTACK *) NULL;
+    n = p->s_stack;
+    
+    /* copy the parent stack from the current item data */
+    while (n != (GISTSTACK *) NULL) {
+	tmp = (GISTSTACK *) palloc(sizeof(GISTSTACK));
+	tmp->gs_child = n->gs_child;
+	tmp->gs_blk = n->gs_blk;
+	tmp->gs_parent = o;
+	o = tmp;
+	n = n->gs_parent;
+    }
+    
+    freestack(p->s_markstk);
+    p->s_markstk = o;
+}
+
+void
+gistrestrpos(IndexScanDesc s)
+{
+    GISTScanOpaque p;
+    GISTSTACK *o, *n, *tmp;
+    
+    s->currentItemData = s->currentMarkData;
+    p = (GISTScanOpaque) s->opaque;
+    if (p->s_flags & GS_MRKBEFORE)
+	p->s_flags |= GS_CURBEFORE;
+    else
+	p->s_flags &= ~GS_CURBEFORE;
+    
+    o = (GISTSTACK *) NULL;
+    n = p->s_markstk;
+    
+    /* copy the parent stack from the current item data */
+    while (n != (GISTSTACK *) NULL) {
+	tmp = (GISTSTACK *) palloc(sizeof(GISTSTACK));
+	tmp->gs_child = n->gs_child;
+	tmp->gs_blk = n->gs_blk;
+	tmp->gs_parent = o;
+	o = tmp;
+	n = n->gs_parent;
+    }
+    
+    freestack(p->s_stack);
+    p->s_stack = o;
+}
+
+void
+gistendscan(IndexScanDesc s)
+{
+    GISTScanOpaque p;
+    
+    p = (GISTScanOpaque) s->opaque;
+    
+    if (p != (GISTScanOpaque) NULL) {
+	freestack(p->s_stack);
+	freestack(p->s_markstk);
+    }
+    
+    gistdropscan(s);
+    /* XXX don't unset read lock -- two-phase locking */
+}
+
+static void
+gistregscan(IndexScanDesc s)
+{
+    GISTScanList l;
+    
+    l = (GISTScanList) palloc(sizeof(GISTScanListData));
+    l->gsl_scan = s;
+    l->gsl_next = GISTScans;
+    GISTScans = l;
+}
+
+static void
+gistdropscan(IndexScanDesc s)
+{
+    GISTScanList l;
+    GISTScanList prev;
+    
+    prev = (GISTScanList) NULL;
+    
+    for (l = GISTScans;
+	 l != (GISTScanList) NULL && l->gsl_scan != s;
+	 l = l->gsl_next) {
+	prev = l;
+    }
+    
+    if (l == (GISTScanList) NULL)
+	elog(WARN, "GiST scan list corrupted -- cannot find 0x%lx", s);
+    
+    if (prev == (GISTScanList) NULL)
+	GISTScans = l->gsl_next;
+    else
+	prev->gsl_next = l->gsl_next;
+    
+    pfree(l);
+}
+
+void
+gistadjscans(Relation r, int op, BlockNumber blkno, OffsetNumber offnum)
+{
+    GISTScanList l;
+    Oid relid;
+    
+    relid = r->rd_id;
+    for (l = GISTScans; l != (GISTScanList) NULL; l = l->gsl_next) {
+	if (l->gsl_scan->relation->rd_id == relid)
+	    gistadjone(l->gsl_scan, op, blkno, offnum);
+    }
+}
+
+/*
+ *  gistadjone() -- adjust one scan for update.
+ *
+ *	By here, the scan passed in is on a modified relation.  Op tells
+ *	us what the modification is, and blkno and offind tell us what
+ *	block and offset index were affected.  This routine checks the
+ *	current and marked positions, and the current and marked stacks,
+ *	to see if any stored location needs to be changed because of the
+ *	update.  If so, we make the change here.
+ */
+static void
+gistadjone(IndexScanDesc s,
+	 int op,
+	 BlockNumber blkno,
+	 OffsetNumber offnum)
+{
+    GISTScanOpaque so;
+    
+    adjustiptr(s, &(s->currentItemData), op, blkno, offnum);
+    adjustiptr(s, &(s->currentMarkData), op, blkno, offnum);
+    
+    so = (GISTScanOpaque) s->opaque;
+    
+    if (op == GISTOP_SPLIT) {
+	adjuststack(so->s_stack, blkno, offnum);
+	adjuststack(so->s_markstk, blkno, offnum);
+    }
+}
+
+/*
+ *  adjustiptr() -- adjust current and marked item pointers in the scan
+ *
+ *	Depending on the type of update and the place it happened, we
+ *	need to do nothing, to back up one record, or to start over on
+ *	the same page.
+ */
+static void
+adjustiptr(IndexScanDesc s,
+	   ItemPointer iptr,
+	   int op,
+	   BlockNumber blkno,
+	   OffsetNumber offnum)
+{
+    OffsetNumber curoff;
+    GISTScanOpaque so;
+    
+    if (ItemPointerIsValid(iptr)) {
+	if (ItemPointerGetBlockNumber(iptr) == blkno) {
+	    curoff = ItemPointerGetOffsetNumber(iptr);
+	    so = (GISTScanOpaque) s->opaque;
+	    
+	    switch (op) {
+	    case GISTOP_DEL:
+		/* back up one if we need to */
+		if (curoff >= offnum) {
+		    
+		    if (curoff > FirstOffsetNumber) {
+			/* just adjust the item pointer */
+			ItemPointerSet(iptr, blkno, OffsetNumberPrev(curoff));
+		    } else {
+			/* remember that we're before the current tuple */
+			ItemPointerSet(iptr, blkno, FirstOffsetNumber);
+			if (iptr == &(s->currentItemData))
+			    so->s_flags |= GS_CURBEFORE;
+			else
+			    so->s_flags |= GS_MRKBEFORE;
+		    }
+		}
+		break;
+		
+	    case GISTOP_SPLIT:
+		/* back to start of page on split */
+		ItemPointerSet(iptr, blkno, FirstOffsetNumber);
+		if (iptr == &(s->currentItemData))
+		    so->s_flags &= ~GS_CURBEFORE;
+		else
+		    so->s_flags &= ~GS_MRKBEFORE;
+		break;
+		
+	    default:
+		elog(WARN, "Bad operation in GiST scan adjust: %d", op);
+	    }
+	}
+    }
+}
+
+/*
+ *  adjuststack() -- adjust the supplied stack for a split on a page in
+ *		     the index we're scanning.
+ *
+ *	If a page on our parent stack has split, we need to back up to the
+ *	beginning of the page and rescan it.  The reason for this is that
+ *	the split algorithm for GiSTs doesn't order tuples in any useful
+ *	way on a single page.  This means on that a split, we may wind up
+ *	looking at some heap tuples more than once.  This is handled in the
+ *	access method update code for heaps; if we've modified the tuple we
+ *	are looking at already in this transaction, we ignore the update
+ *	request.
+ */
+/*ARGSUSED*/
+static void
+adjuststack(GISTSTACK *stk,
+	    BlockNumber blkno,
+	    OffsetNumber offnum)
+{
+    while (stk != (GISTSTACK *) NULL) {
+	if (stk->gs_blk == blkno)
+	    stk->gs_child = FirstOffsetNumber;
+	
+	stk = stk->gs_parent;
+    }
+}