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/* Copyright (C) 2003 MySQL AB
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
#define DBTUX_STAT_CPP
#include "Dbtux.hpp"
void
Dbtux::execREAD_PSEUDO_REQ(Signal* signal)
{
jamEntry();
ScanOpPtr scanPtr;
scanPtr.i = signal->theData[0];
c_scanOpPool.getPtr(scanPtr);
if (signal->theData[1] == AttributeHeader::RECORDS_IN_RANGE) {
jam();
statRecordsInRange(scanPtr, &signal->theData[0]);
} else {
ndbassert(false);
}
}
/*
* Estimate entries in range. Scan is at first entry. Search for last
* entry i.e. start of descending scan. Use the 2 positions to estimate
* entries before and after the range. Finally get entries in range by
* subtracting from total. Errors come from imperfectly balanced tree
* and from uncommitted entries which differ only in tuple version.
*
* Returns 4 Uint32 values: 0) total entries 1) in range 2) before range
* 3) after range. 1-3) are estimates and need not add up to 0).
*/
void
Dbtux::statRecordsInRange(ScanOpPtr scanPtr, Uint32* out)
{
ScanOp& scan = *scanPtr.p;
Frag& frag = *c_fragPool.getPtr(scan.m_fragPtrI);
TreeHead& tree = frag.m_tree;
// get first and last position
TreePos pos1 = scan.m_scanPos;
TreePos pos2;
{ // as in scanFirst()
TreeHead& tree = frag.m_tree;
setKeyAttrs(frag);
const unsigned idir = 1;
const ScanBound& bound = *scan.m_bound[idir];
ScanBoundIterator iter;
bound.first(iter);
for (unsigned j = 0; j < bound.getSize(); j++) {
jam();
c_dataBuffer[j] = *iter.data;
bound.next(iter);
}
searchToScan(frag, c_dataBuffer, scan.m_boundCnt[idir], true, pos2);
// committed read (same timeslice) and range not empty
ndbrequire(pos2.m_loc != NullTupLoc);
}
out[0] = frag.m_tree.m_entryCount;
out[2] = getEntriesBeforeOrAfter(frag, pos1, 0);
out[3] = getEntriesBeforeOrAfter(frag, pos2, 1);
if (pos1.m_loc == pos2.m_loc) {
ndbrequire(pos2.m_pos >= pos1.m_pos);
out[1] = pos2.m_pos - pos1.m_pos + 1;
} else {
Uint32 rem = out[2] + out[3];
if (out[0] > rem) {
out[1] = out[0] - rem;
} else {
// random guess one node apart
out[1] = tree.m_maxOccup;
}
}
}
/*
* Estimate number of entries strictly before or after given position.
* Each branch to right direction wins parent node and the subtree on
* the other side. Subtree entries is estimated from depth and total
* entries by assuming that the tree is perfectly balanced.
*/
Uint32
Dbtux::getEntriesBeforeOrAfter(Frag& frag, TreePos pos, unsigned idir)
{
NodeHandle node(frag);
selectNode(node, pos.m_loc);
Uint16 path[MaxTreeDepth + 1];
unsigned depth = getPathToNode(node, path);
ndbrequire(depth != 0 && depth <= MaxTreeDepth);
TreeHead& tree = frag.m_tree;
Uint32 cnt = 0;
Uint32 tot = tree.m_entryCount;
unsigned i = 0;
// contribution from levels above
while (i + 1 < depth) {
unsigned occup2 = (path[i] >> 8);
unsigned side = (path[i + 1] & 0xFF);
// subtree of this node has about half the entries
tot = tot >= occup2 ? (tot - occup2) / 2 : 0;
// branch to other side wins parent and a subtree
if (side != idir) {
cnt += occup2;
cnt += tot;
}
i++;
}
// contribution from this node
unsigned occup = (path[i] >> 8);
ndbrequire(pos.m_pos < occup);
if (idir == 0) {
if (pos.m_pos != 0)
cnt += pos.m_pos - 1;
} else {
cnt += occup - (pos.m_pos + 1);
}
// contribution from levels below
tot = tot >= occup ? (tot - occup) / 2 : 0;
cnt += tot;
return cnt;
}
/*
* Construct path to given node. Returns depth. Root node has path
* 2 and depth 1. In general the path is 2{0,1}* where 0,1 is the side
* (left,right branch). In addition the occupancy of each node is
* returned in the upper 8 bits.
*/
unsigned
Dbtux::getPathToNode(NodeHandle node, Uint16* path)
{
TupLoc loc = node.m_loc;
unsigned i = MaxTreeDepth;
while (loc != NullTupLoc) {
jam();
selectNode(node, loc);
path[i] = node.getSide() | (node.getOccup() << 8);
loc = node.getLink(2);
ndbrequire(i != 0);
i--;
}
unsigned depth = MaxTreeDepth - i;
unsigned j = 0;
while (j < depth) {
path[j] = path[i + 1 + j];
j++;
}
path[j] = 0xFFFF; // catch bug
return depth;
}
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