/**
* Copyright (C) 2009-2013 FoundationDB, LLC
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package com.foundationdb.sql.optimizer.rule.join_enum;
import com.foundationdb.server.error.FailedJoinGraphCreationException;
import com.foundationdb.sql.optimizer.plan.*;
import static com.foundationdb.sql.optimizer.plan.JoinNode.JoinType;
import com.foundationdb.server.error.UnsupportedSQLException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.*;
/**
* Hypergraph-based dynamic programming for join ordering enumeration.
* See "Dynamic Programming Strikes Back", doi:10.1145/1376616.1376672
*
* Summary:<ul>
* <li>Nodes are joined tables.</li>
* <li>Edges represent predicates and operator (LEFT, FULL OUTER,
* SEMI, ...) reordering constraints.</li>
* <li>DP happens by considering larger
* sets made up from pairs of connected (based on edges) subsets.</li></ul>
*/
public abstract class DPhyp<P>
{
private static final Logger logger = LoggerFactory.getLogger(DPhyp.class);
// The leaves of the join tree: tables, derived tables, and
// possibly joins handled atomically wrt this phase.
private List<Joinable> tables;
// The join operators, from JOINs and WHERE clause.
private List<JoinOperator> operators, evaluateOperators, outsideOperators, oneSidedJoinOperators;
// The hypergraph: since these are unordered, traversal pattern is
// to go through in order pairing with adjacent (complement bit 1).
private long[] edges;
private int noperators, nedges;
// Indexes for leaves and their constituent tables.
private Map<Joinable,Long> tableBitSets;
// The "plan class" is the set of retained plans for the given tables.
private Object[] plans;
@SuppressWarnings("unchecked")
private P getPlan(long s) {
return (P)plans[(int)s];
}
private void setPlan(long s, P plan) {
if (logger.isTraceEnabled())
logger.trace("{}: {}", JoinableBitSet.toString(s, tables), plan);
plans[(int)s] = plan;
}
public P run(Joinable root, ConditionList whereConditions) {
init(root, whereConditions);
return solve();
}
/** Return minimal set of neighbors of <code>s</code> not in the exclusion set. */
// TODO: Need to eliminate subsumed hypernodes.
public long neighborhood(long s, long exclude) {
exclude = JoinableBitSet.union(s, exclude);
long result = 0;
for (int e = 0; e < nedges; e++) {
if (JoinableBitSet.isSubset(edges[e], s) &&
!JoinableBitSet.overlaps(edges[e^1], exclude)) {
result |= JoinableBitSet.minSubset(edges[e^1]);
}
}
return result;
}
/** Run dynamic programming and return best overall plan(s). */
public P solve() {
int ntables = tables.size();
assert (ntables < 31);
plans = new Object[1 << ntables];
for (int pass = 1; pass <= 2; pass++) {
// Start with single tables.
for (int i = 0; i < ntables; i++) {
long bitset = JoinableBitSet.of(i);
setPlan(bitset, evaluateTable(bitset, tables.get(i)));
}
for (int i = ntables - 1; i >= 0; i--) {
long ts = JoinableBitSet.of(i);
emitCsg(ts);
enumerateCsgRec(ts, JoinableBitSet.through(i));
}
P plan = getPlan(plans.length-1); // One that does all the joins together.
if (plan != null)
return plan;
if (logger.isTraceEnabled()) {
StringBuilder str = new StringBuilder("Plan not complete");
for (int i = 1; i < plans.length-1; i++) {
if (plans[i] != null) {
str.append('\n').append(Integer.toString(i, 2))
.append(": ").append(plans[i]);
}
}
logger.trace("{}", str.toString());
}
// dphyp should be able to create a graph so long as it's not a true cross product
// (ie. join with no conditions)
if (pass != 1) {
throw new FailedJoinGraphCreationException();
}
addExtraEdges();
Arrays.fill(plans, null);
}
return null;
}
/** Recursively extend the given connected subgraph. */
public void enumerateCsgRec(long s1, long exclude) {
long neighborhood = neighborhood(s1, exclude);
if (neighborhood == 0) return;
long subset = 0;
do {
subset = JoinableBitSet.nextSubset(subset, neighborhood);
long next = JoinableBitSet.union(s1, subset);
if (getPlan(next) != null)
emitCsg(next);
} while (!JoinableBitSet.equals(subset, neighborhood));
subset = 0; // Start over.
exclude = JoinableBitSet.union(exclude, neighborhood);
do {
subset = JoinableBitSet.nextSubset(subset, neighborhood);
long next = JoinableBitSet.union(s1, subset);
enumerateCsgRec(next, exclude);
} while (!JoinableBitSet.equals(subset, neighborhood));
}
/** Generate seeds for connected complements of the given connected subgraph. */
public void emitCsg(long s1) {
long exclude = JoinableBitSet.union(s1, JoinableBitSet.through(JoinableBitSet.min(s1)));
long neighborhood = neighborhood(s1, exclude);
if (neighborhood == 0) return;
for (int i = tables.size() - 1; i >= 0; i--) {
long s2 = JoinableBitSet.of(i);
if (JoinableBitSet.overlaps(neighborhood, s2)) {
boolean connected = false;
for (int e = 0; e < nedges; e+=2) {
if (isEvaluateOperator(s1, s2, e)) {
connected = true;
break;
}
}
if (connected)
emitCsgCmp(s1, s2);
enumerateCmpRec(s1, s2, exclude);
}
}
}
/** Extend complement <code>s2</code> until a csg-cmp pair is
* reached, excluding the given tables to avoid duplicate
* enumeration, */
public void enumerateCmpRec(long s1, long s2, long exclude) {
long neighborhood = neighborhood(s2, exclude);
if (neighborhood == 0) return;
long subset = 0;
do {
subset = JoinableBitSet.nextSubset(subset, neighborhood);
long next = JoinableBitSet.union(s2, subset);
if (getPlan(next) != null) {
boolean connected = false;
for (int e = 0; e < nedges; e+=2) {
if (isEvaluateOperator(s1, next, e)) {
connected = true;
break;
}
}
if (connected)
emitCsgCmp(s1, next);
}
} while (!JoinableBitSet.equals(subset, neighborhood));
subset = 0; // Start over.
exclude = JoinableBitSet.union(exclude, neighborhood);
do {
subset = JoinableBitSet.nextSubset(subset, neighborhood);
long next = JoinableBitSet.union(s2, subset);
enumerateCmpRec(s1, next, exclude);
} while (!JoinableBitSet.equals(subset, neighborhood));
}
/** Emit the connected subgraph / complement pair.
* That is, build and cost a plan that joins them and maybe
* register it as the new best such plan for the pair.
*/
public void emitCsgCmp(long s1, long s2) {
P p1 = getPlan(s1);
P p2 = getPlan(s2);
long s = JoinableBitSet.union(s1, s2);
JoinType join12 = JoinType.INNER, join21 = JoinType.INNER;
evaluateOperators.clear();
oneSidedJoinOperators.clear();
boolean connected = false;
for (int e = 0; e < nedges; e +=2) {
boolean isEvaluate = isEvaluateOperator(s1, s2, e);
boolean isRelevant = isRelevant(s1, s2, e);
connected |= isEvaluate;
if (isEvaluate || isRelevant) {
// The one that produced this edge.
JoinOperator operator = operators.get(e/2);
JoinType joinType = operator.getJoinType();
if (joinType != JoinType.INNER) {
join12 = joinType;
join21 = commuteJoinType(joinType);
}
evaluateOperators.add(operator);
}
}
if (!connected) {
return;
}
outsideOperators.clear();
for (JoinOperator operator : operators) {
if (JoinableBitSet.overlaps(operator.predicateTables, s) &&
!JoinableBitSet.isSubset(operator.predicateTables, s) &&
!evaluateOperators.contains(operator))
// An operator involving tables in this join with others.
outsideOperators.add(operator);
}
P plan = getPlan(s);
if (join12 != null)
plan = evaluateJoin(s1, p1, s2, p2, s, plan,
join12, evaluateOperators, outsideOperators);
if (join21 != null)
plan = evaluateJoin(s2, p2, s1, p1, s, plan,
join21, evaluateOperators, outsideOperators);
setPlan(s, plan);
}
/**
* This checks if all tables necessary for an edge are available and that
* it is the edge's first time appearing
*
* EXPLAIN:
* cases:
* no sided edge gets true only on first join
* one sided edges are only added first time table is available
* if both sides of the edge exist on one side of the join already it must have already been added
* else if both sides connect both sets then true
*/
private boolean isRelevant(long s1, long s2, int e) {
if ((JoinableBitSet.count(s1) == 1 && JoinableBitSet.count(s2) == 1) &&
(JoinableBitSet.isEmpty(edges[e]) && JoinableBitSet.isEmpty(edges[e ^ 1]))) {
return true;
}
if (JoinableBitSet.count(s1) == 1 && ((edges[e] | edges[e ^ 1]) == s1)) {
return true;
}
if (JoinableBitSet.count(s2) == 1 && ((edges[e] | edges[e ^ 1]) == s2))
return true;
if (JoinableBitSet.isSubset(edges[e] | edges[e ^ 1], s1) || JoinableBitSet.isSubset(edges[e] | edges[e ^ 1], s2)) {
return false;
}
return JoinableBitSet.isSubset(edges[e] | edges[e ^ 1], s1 | s2);
}
/**
* This checks if the edge connects two unconnected sets
*
* EXPLAIN:
* cases false if either side of edge is empty since it cannot connect anything
* this must be done because the empty set is the subset of all sets
* if edge connects the two sides return true
*/
public boolean isEvaluateOperator(long s1, long s2, int e) {
if (JoinableBitSet.isEmpty(edges[e]) || JoinableBitSet.isEmpty(edges[e ^ 1])) {
return false;
}
return JoinableBitSet.isSubset(edges[e], s1) && JoinableBitSet.isSubset(edges[e ^ 1], s2) ||
JoinableBitSet.isSubset(edges[e], s2) && JoinableBitSet.isSubset(edges[e ^ 1], s1);
}
/** Return the best plan for the one-table initial state. */
public abstract P evaluateTable(long bitset, Joinable table);
/** Adjust best plan <code>existing</code> for the join of
* <code>p1</code> and <code>p2</code> with given type and
* conditions taken from the given joins.
*/
public abstract P evaluateJoin(long bitset1, P p1, long bitset2, P p2, long bitsetJoined, P existing,
JoinType joinType, Collection<JoinOperator> joins, Collection<JoinOperator> outsideJoins);
/** Return a leaf of the tree. */
public Joinable getTable(int index) {
return tables.get(index);
}
public long getTableBit (Joinable join) {
return tableBitSets.get(join);
}
public Map<Joinable, Long> getTableBitSets() {
return tableBitSets;
}
public long rootJoinLeftTables() {
JoinOperator lastOp = null;
for (JoinOperator op : operators) {
if (op.getJoin() == null) break;
lastOp = op;
}
return lastOp.leftTables;
}
/** Initialize state from the given join tree. */
// TODO: Need to do something about disconnected overall. The
// cross-product isn't going to do very well no matter what. Maybe
// just break up the graph _before_ calling all this?
public void init(Joinable root, ConditionList whereConditions) {
tables = new ArrayList<>();
addTables(root, tables);
int ntables = tables.size();
if (ntables > 30)
// TODO: Need to select some simpler algorithm that scales better.
throw new UnsupportedSQLException("Too many tables in query: " + ntables,
null);
tableBitSets = new HashMap<>(ntables);
for (int i = 0; i < ntables; i++) {
Joinable table = tables.get(i);
Long bitset = JoinableBitSet.of(i);
tableBitSets.put(table, bitset);
if (table instanceof TableJoins) {
for (TableSource joinedTable : ((TableJoins)table).getTables()) {
tableBitSets.put(joinedTable, bitset);
}
}
else if (table instanceof TableGroupJoinTree) {
for (TableGroupJoinTree.TableGroupJoinNode node : (TableGroupJoinTree)table) {
tableBitSets.put(node.getTable(), bitset);
}
}
}
ExpressionTables visitor = new ExpressionTables(tableBitSets);
noperators = 0;
JoinOperator rootOp = initSES(root, visitor);
if (whereConditions != null)
noperators += whereConditions.size(); // Maximum possible addition.
operators = new ArrayList<>(noperators);
nedges = noperators * 2;
edges = new long[nedges];
calcTES(rootOp);
noperators = operators.size();
if (whereConditions != null)
addWhereConditions(whereConditions, visitor, JoinableBitSet.empty());
int iop = 0;
while (iop < noperators) {
JoinOperator op = operators.get(iop);
if (op.allInnerJoins) {
// Inner joins can treat join conditions only among them like WHERE
// conditions, as independent edges.
if (op.joinConditions != null) {
// Join conditions for an INNER subtree.
addJoinConditions(op.joinConditions, visitor,
JoinableBitSet.empty());
}
if ((op.parent != null) && !op.parent.allInnerJoins &&
(op.parent.joinConditions != null)) {
// Parent join conditions for one side that's INNER.
long otherSide = (op == op.parent.left) ?
op.parent.rightTables :
op.parent.leftTables;
addJoinConditions(op.parent.joinConditions, visitor, otherSide);
}
if (JoinableBitSet.isEmpty(op.tes)) {
// Remove this operator that won't contribute any edges.
operators.remove(iop);
noperators--;
System.arraycopy(edges, (iop + 1) * 2,
edges, iop * 2,
(operators.size() - iop) * 2);
continue;
}
}
iop++;
}
noperators = operators.size();
nedges = noperators * 2;
if (logger.isTraceEnabled()) {
StringBuilder str = new StringBuilder("Operators and edges:");
for (int i = 0; i < noperators; i++) {
str.append('\n')
.append(operators.get(i).toString(tables)).append('\n')
.append(JoinableBitSet.toString(edges[i*2], tables)).append(" <-> ")
.append(JoinableBitSet.toString(edges[i*2+1], tables));
}
logger.trace("{}", str.toString());
}
evaluateOperators = new ArrayList<>(noperators);
outsideOperators = new ArrayList<>(noperators);
oneSidedJoinOperators = new ArrayList<>(noperators);
}
public static void addTables(Joinable n, List<Joinable> tables) {
if (n instanceof JoinNode) {
JoinNode join = (JoinNode)n;
addTables(join.getLeft(), tables);
addTables(join.getRight(), tables);
}
else {
tables.add(n);
}
}
public static class JoinOperator {
JoinNode join; // If from an actual join.
ConditionList joinConditions;
JoinOperator left, right, parent;
long leftTables, rightTables, predicateTables;
long tes;
boolean allInnerJoins;
public JoinOperator(JoinNode join) {
this.join = join;
joinConditions = join.getJoinConditions() == null ? null : new ConditionList(join.getJoinConditions());
allInnerJoins = (join.getJoinType() == JoinType.INNER);
}
public JoinOperator(ConditionExpression condition, long leftTables, long rightTables) {
joinConditions = new ConditionList(1);
joinConditions.add(condition);
this.leftTables = leftTables;
this.rightTables = rightTables;
this.tes = this.predicateTables = this.getTables();
}
public JoinOperator() {
joinConditions = new ConditionList(0);
}
public JoinOperator(JoinOperator join) {
this.join = join.join;
this.joinConditions = join.joinConditions == null ? null : new ConditionList(join.joinConditions);
this.left = join.left;
this.right = join.right;
this.parent = join.parent;
leftTables = join.leftTables;
rightTables = join.rightTables;
predicateTables = join.predicateTables;
tes = join.tes;
allInnerJoins = join.allInnerJoins;
}
public long getTables() {
return JoinableBitSet.union(leftTables, rightTables);
}
public JoinNode getJoin() {
return join;
}
public ConditionList getJoinConditions() {
return joinConditions;
}
public JoinType getJoinType() {
if (join != null)
return join.getJoinType();
else
return JoinType.INNER;
}
public String toString(List<Joinable> tables) {
return toString();
}
public String toString() {
if (join != null)
return join.toString();
else
return joinConditions.toString();
}
}
/** Starting state of the TES is just those tables used syntactically. */
protected JoinOperator initSES(Joinable n, ExpressionTables visitor) {
if (n instanceof JoinNode) {
JoinNode join = (JoinNode)n;
JoinOperator op = new JoinOperator(join);
Joinable left = join.getLeft();
JoinOperator leftOp = initSES(left, visitor);
boolean childAllInnerJoins = false;
if (leftOp != null) {
leftOp.parent = op;
op.left = leftOp;
op.leftTables = leftOp.getTables();
if (leftOp.allInnerJoins)
childAllInnerJoins = true;
else
op.allInnerJoins = false;
}
else {
op.leftTables = getTableBit(left);
}
Joinable right = join.getRight();
JoinOperator rightOp = initSES(right, visitor);
if (rightOp != null) {
rightOp.parent = op;
op.right = rightOp;
op.rightTables = rightOp.getTables();
if (rightOp.allInnerJoins)
childAllInnerJoins = true;
else
op.allInnerJoins = false;
}
else {
op.rightTables = getTableBit(right);
}
op.predicateTables = visitor.getTables(op.joinConditions);
if (visitor.wasNullTolerant() && !op.allInnerJoins)
op.tes = op.getTables();
else
op.tes = JoinableBitSet.intersection(op.getTables(), op.predicateTables);
noperators++;
if ((op.joinConditions != null) && (op.allInnerJoins || childAllInnerJoins))
noperators += op.joinConditions.size(); // Might move some.
return op;
}
return null;
}
/** Extend TES for join operators based on reordering conflicts. */
public void calcTES(JoinOperator op) {
if (op != null) {
calcTES(op.left);
calcTES(op.right);
addConflicts(op, op.left, true);
addConflicts(op, op.right, false);
long r = JoinableBitSet.intersection(op.tes, op.rightTables);
long l = JoinableBitSet.difference(op.tes, r);
int o = operators.size();
operators.add(op);
// Add an edge for the TES of this join operator.
edges[o*2] = l;
edges[o*2+1] = r;
}
}
/** Add conflicts to <code>o1</code> from descendant <code>o2</code>. */
protected static void addConflicts(JoinOperator o1, JoinOperator o2, boolean left) {
if (o2 != null) {
if (left ? leftConflict(o2, o1) : rightConflict(o1, o2)) {
o1.tes = JoinableBitSet.union(o1.tes, o2.tes);
}
addConflicts(o1, o2.left, left);
addConflicts(o1, o2.right, left);
}
}
/** Is there a left ordering conflict? */
protected static boolean leftConflict(JoinOperator o2, JoinOperator o1) {
return JoinableBitSet.overlaps(o1.predicateTables, rightTables(o1, o2)) &&
operatorConflict(o2.getJoinType(), o1.getJoinType());
}
/** Is there a right ordering conflict? */
protected static boolean rightConflict(JoinOperator o1, JoinOperator o2) {
return JoinableBitSet.overlaps(o1.predicateTables, leftTables(o1, o2)) &&
operatorConflict(o1.getJoinType(), o2.getJoinType());
}
/** Does parent operator <code>o1</code> conflict with child <code>o2</code>? */
protected static boolean operatorConflict(JoinType o1, JoinType o2) {
switch (o1) {
case INNER:
return (o2 == JoinType.FULL_OUTER);
case LEFT:
return (o2 != JoinType.LEFT);
case FULL_OUTER:
return (o2 == JoinType.INNER);
case RIGHT:
assert false; // Should not see right join at this point.
default:
return true;
}
}
/** All the left tables on the path from <code>o2</code> (inclusive)
* to <code>o1</code> (exclusive). */
protected static long leftTables(JoinOperator o1, JoinOperator o2) {
long result = JoinableBitSet.empty();
for (JoinOperator o3 = o2; o3 != o1; o3 = o3.parent)
result = JoinableBitSet.union(result, o3.leftTables);
if (isCommutative(o2.getJoinType()))
result = JoinableBitSet.union(result, o2.rightTables);
return result;
}
/** All the right tables on the path from <code>o2</code> (inclusive)
* to <code>o1</code> (exclusive). */
protected static long rightTables(JoinOperator o1, JoinOperator o2) {
long result = JoinableBitSet.empty();
for (JoinOperator o3 = o2; o3 != o1; o3 = o3.parent)
result = JoinableBitSet.union(result, o3.rightTables);
if (isCommutative(o2.getJoinType()))
result = JoinableBitSet.union(result, o2.leftTables);
return result;
}
/** Does this operator commute? */
protected static boolean isCommutative(JoinType joinType) {
return (commuteJoinType(joinType) != null);
}
protected static JoinType commuteJoinType(JoinType joinType) {
switch (joinType) {
case INNER:
case FULL_OUTER:
return joinType;
case SEMI_INNER_ALREADY_DISTINCT:
return JoinType.INNER;
case SEMI_INNER_IF_DISTINCT:
return JoinType.INNER_NEED_DISTINCT;
default:
return null;
}
}
/** Get join conditions from join clauses. */
protected void addJoinConditions(ConditionList whereConditions,
ExpressionTables visitor,
long excludeTables) {
Iterator<ConditionExpression> iter = whereConditions.iterator();
// NOTE: conditions on the join clause must be added somewhere when initializing the operators,
// or they won't end up in the resulting plan.
while (iter.hasNext()) {
ConditionExpression condition = iter.next();
if (condition instanceof ComparisonCondition) {
ComparisonCondition comp = (ComparisonCondition)condition;
long columnTables = columnReferenceTable(comp.getLeft());
if (!JoinableBitSet.isEmpty(columnTables) &&
!JoinableBitSet.overlaps(columnTables, excludeTables)) {
long rhs = visitor.getTables(comp.getRight());
if (visitor.wasNullTolerant() ||
JoinableBitSet.overlaps(rhs, excludeTables))
continue;
if (addInnerJoinCondition(condition, columnTables, rhs)) {
iter.remove();
continue;
}
}
columnTables = columnReferenceTable(comp.getRight());
if (!JoinableBitSet.isEmpty(columnTables) &&
!JoinableBitSet.overlaps(columnTables, excludeTables)) {
long lhs = visitor.getTables(comp.getLeft());
if (visitor.wasNullTolerant() ||
JoinableBitSet.overlaps(lhs, excludeTables))
continue;
if (addInnerJoinCondition(condition, columnTables, lhs)) {
iter.remove();
continue;
}
}
} else {
// NOTE: this could be something weird like f(c1,c2,c3,c4) = 5, I'm just going to put the first
// source on the left, and the rest on the right.
// TODO the dphyper.pdf explains how to handle this situation, by switch to having edges be of the form
// (u,v,w) where u and v are conditions on the left or right side respectively, but the w conditions can
// be on either side.
long tables = visitor.getTables(condition);
long left = JoinableBitSet.minSubset(tables);
long remaining = JoinableBitSet.difference(tables, left);
if (!JoinableBitSet.overlaps(tables, excludeTables)) {
if (addInnerJoinCondition(condition, left, remaining)) {
iter.remove();
}
}
}
}
}
/** Add an edge for the tables in this simple condition.
* This only applies to conditions that appear on an inner join
*/
protected boolean addInnerJoinCondition(ConditionExpression condition,
long columnTables, long comparisonTables) {
if (!JoinableBitSet.overlaps(columnTables, comparisonTables)) {
JoinOperator op = new JoinOperator(condition, columnTables, comparisonTables);
int o = operators.size();
operators.add(op);
edges[o*2] = columnTables;
edges[o*2+1] = comparisonTables;
return true;
}
return false;
}
/** Get join conditions from top-level WHERE predicates. */
protected void addWhereConditions(ConditionList whereConditions,
ExpressionTables visitor,
long excludeTables) {
Iterator<ConditionExpression> iter = whereConditions.iterator();
while (iter.hasNext()) {
ConditionExpression condition = iter.next();
// TODO: When optimizer supports more predicates
// interestingly, can recognize them, including
// generalized hypergraph triples.
if (condition instanceof ComparisonCondition) {
ComparisonCondition comp = (ComparisonCondition)condition;
long columnTables = columnReferenceTable(comp.getLeft());
if (!JoinableBitSet.isEmpty(columnTables) &&
!JoinableBitSet.overlaps(columnTables, excludeTables)) {
long rhs = visitor.getTables(comp.getRight());
if (visitor.wasNullTolerant() ||
JoinableBitSet.overlaps(rhs, excludeTables))
continue;
if (addWhereCondition(condition, columnTables, rhs)) {
iter.remove();
continue;
}
}
columnTables = columnReferenceTable(comp.getRight());
if (!JoinableBitSet.isEmpty(columnTables) &&
!JoinableBitSet.overlaps(columnTables, excludeTables)) {
long lhs = visitor.getTables(comp.getLeft());
if (visitor.wasNullTolerant() ||
JoinableBitSet.overlaps(lhs, excludeTables))
continue;
if (addWhereCondition(condition, columnTables, lhs)) {
iter.remove();
continue;
}
}
}
}
}
/** Is this a single column in a known table? */
protected long columnReferenceTable(ExpressionNode node) {
if (node instanceof ColumnExpression) {
Long bitset = tableBitSets.get(((ColumnExpression)node).getTable());
if (bitset != null) {
return bitset;
}
}
return JoinableBitSet.empty();
}
/** Add an edge for the tables in this simple condition.
* There are no extra reordering constraints, since this is just a
* WHERE condition. Furthermore, its tables ought to be in INNER
* joins, since such a null-intolerent condition implies that they
* aren't missing.
*/
protected boolean addWhereCondition(ConditionExpression condition,
long columnTables, long comparisonTables) {
if (!JoinableBitSet.isEmpty(comparisonTables) &&
!JoinableBitSet.overlaps(columnTables, comparisonTables)) {
JoinOperator op = new JoinOperator(condition, columnTables, comparisonTables);
int o = operators.size();
operators.add(op);
edges[o*2] = columnTables;
edges[o*2+1] = comparisonTables;
return true;
}
return false;
}
/** Compute tables used in join predicate. */
public static class ExpressionTables implements ExpressionVisitor, PlanVisitor {
Map<Joinable,Long> tableBitSets;
long result;
boolean nullTolerant;
public ExpressionTables(Map<Joinable,Long> tableBitSets) {
this.tableBitSets = tableBitSets;
}
public long getTables(ConditionList conditions) {
result = JoinableBitSet.empty();
nullTolerant = false;
if (conditions != null) {
for (ConditionExpression cond : conditions) {
cond.accept(this);
}
}
return result;
}
public long getTables(ExpressionNode node) {
result = JoinableBitSet.empty();
nullTolerant = false;
node.accept(this);
return result;
}
public boolean wasNullTolerant() {
return nullTolerant;
}
@Override
public boolean visitEnter(ExpressionNode n) {
return visit(n);
}
@Override
public boolean visitLeave(ExpressionNode n) {
return true;
}
@Override
public boolean visit(ExpressionNode n) {
if (n instanceof ColumnExpression) {
Long bitset = tableBitSets.get(((ColumnExpression)n).getTable());
if (bitset != null) {
result = JoinableBitSet.union(result, bitset);
}
}
else if (!nullTolerant && (n instanceof FunctionExpression)) {
String fname = ((FunctionExpression)n).getFunction();
if ("isNull".equals(fname) || "isUnknown".equals(fname) ||
"isTrue".equals(fname) || "isFalse".equals(fname) ||
"COALESCE".equals(fname) || "ifnull".equals(fname))
nullTolerant = true;
}
return true;
}
@Override
public boolean visitEnter(PlanNode n) {
return visit(n);
}
@Override
public boolean visitLeave(PlanNode n) {
return true;
}
@Override
public boolean visit(PlanNode n) {
return true;
}
}
/** Add edges to make the hypergraph connected, using the stuck state. */
protected void addExtraEdges() {
// Get all the hypernodes that are not subsets of some filled hypernode.
BitSet maximal = new BitSet(plans.length);
for (int i = 0; i < plans.length; i++) {
if (plans[i] != null) {
maximal.set(i);
}
}
for (int i = plans.length - 1; i > 2; i--) { // (3 is the smallest with subsets)
if (maximal.get(i)) {
long subset = JoinableBitSet.empty();
while (true) {
subset = JoinableBitSet.nextSubset(subset, i);
if (JoinableBitSet.equals(subset, i)) break;
maximal.clear((int)subset);
}
}
}
int count = maximal.cardinality();
assert (count > 1) : "Found less than 2 unconnected subgraphs";
noperators += count - 1;
nedges = noperators * 2;
if (edges.length < nedges) { // Length was a conservative guess and might be large enough already.
long[] newEdges = new long[nedges];
System.arraycopy(edges, 0, newEdges, 0, edges.length);
edges = newEdges;
}
// Just connect them all up. This is by no means an optimal
// set of new edges, but the plan is trouble to begin with
// since it involved a cross product. Would need something
// like a min cut hypergraph partition.
long left = JoinableBitSet.empty();
int i = -1;
while (true) {
i = maximal.nextSetBit(i+1);
if (i < 0) break;
if (JoinableBitSet.isEmpty(left)) {
left = i;
}
else {
addExtraEdge(left, i);
left = JoinableBitSet.union(left, i);
}
}
assert (noperators == operators.size());
}
protected void addExtraEdge(long left, long right) {
if (logger.isTraceEnabled())
logger.trace("Extra: {} <-> {}",
JoinableBitSet.toString(left, tables) +
JoinableBitSet.toString(right, tables));
JoinOperator op = new JoinOperator();
op.leftTables = left;
op.rightTables = right;
int o = operators.size();
operators.add(op);
edges[o*2] = left;
edges[o*2+1] = right;
}
}