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[SPARK-4937][SQL] Comment for the newly optimization rules in BooleanSimplification #4086

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[SPARK-4937][SQL] Comment for the newly optimization rules in BooleanSimplification #4086

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2d3406e
added comment for spark-4937
scwf Jan 17, 2015
aaf89f6
code style issue
scwf Jan 17, 2015
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18 changes: 16 additions & 2 deletions sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -311,13 +311,20 @@ object BooleanSimplification extends Rule[LogicalPlan] with PredicateHelper {
// a && a => a
case (l, r) if l fastEquals r => l
case (_, _) =>
/* Do optimize for predicates using formula (a || b) && (a || c) => a || (b && c)
* 1. Split left and right to get the disjunctive predicates,
* i.e. lhsSet = (a, b), rhsSet = (a, c)
* 2. Find the common predict between lhsSet and rhsSet, i.e. common = (a)
* 3. Remove common predict from lhsSet and rhsSet, i.e. ldiff = (b), rdiff = (c)
* 4. Apply the formula, get the optimized predict: common || (ldiff && rdiff)
*/
val lhsSet = splitDisjunctivePredicates(left).toSet
val rhsSet = splitDisjunctivePredicates(right).toSet
val common = lhsSet.intersect(rhsSet)
val ldiff = lhsSet.diff(common)
val rdiff = rhsSet.diff(common)
if (ldiff.size == 0 || rdiff.size == 0) {
// a && (a || b)
// a && (a || b) => a
common.reduce(Or)
} else {
// (a || b || c || ...) && (a || b || d || ...) && (a || b || e || ...) ... =>
Expand All @@ -339,13 +346,20 @@ object BooleanSimplification extends Rule[LogicalPlan] with PredicateHelper {
// a || a => a
case (l, r) if l fastEquals r => l
case (_, _) =>
/* Do optimize for predicates using formula (a && b) || (a && c) => a && (b || c)
* 1. Split left and right to get the conjunctive predicates,
* i.e. lhsSet = (a, b), rhsSet = (a, c)
* 2. Find the common predict between lhsSet and rhsSet, i.e. common = (a)
* 3. Remove common predict from lhsSet and rhsSet, i.e. ldiff = (b), rdiff = (c)
* 4. Apply the formula, get the optimized predict: common && (ldiff || rdiff)
*/
val lhsSet = splitConjunctivePredicates(left).toSet
val rhsSet = splitConjunctivePredicates(right).toSet
val common = lhsSet.intersect(rhsSet)
val ldiff = lhsSet.diff(common)
val rdiff = rhsSet.diff(common)
if ( ldiff.size == 0 || rdiff.size == 0) {
// a || (b && a)
// a || (b && a) => a
common.reduce(And)
} else {
// (a && b && c && ...) || (a && b && d && ...) || (a && b && e && ...) ... =>
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