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CALCITE-1790 Simplify boolean CASE into AND/OR #450

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CALCITE-1790 Simplify boolean CASE into AND/OR #450

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81 changes: 51 additions & 30 deletions core/src/main/java/org/apache/calcite/rex/RexSimplify.java
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Original file line number Diff line number Diff line change
Expand Up @@ -407,7 +407,6 @@ private RexNode simplifyCase(RexCall call) {
}
return last;
}
trueFalse:
if (call.getType().getSqlTypeName() == SqlTypeName.BOOLEAN) {
// Optimize CASE where every branch returns constant true or constant
// false.
Expand Down Expand Up @@ -448,45 +447,67 @@ private RexNode simplifyCase(RexCall call) {
return disjunction;
}
}
// 2) Another simplification
// CASE
// WHEN p1 THEN TRUE
// WHEN p2 THEN FALSE
// WHEN p3 THEN TRUE
// ELSE FALSE
// END
// if p1...pn cannot be nullable
for (Ord<Pair<RexNode, RexNode>> pair : Ord.zip(pairs)) {
if (pair.e.getKey().getType().isNullable()) {
break trueFalse;
}
if (!pair.e.getValue().isAlwaysTrue()
&& !pair.e.getValue().isAlwaysFalse()
&& (!unknownAsFalse || !RexUtil.isNull(pair.e.getValue()))) {
break trueFalse;

if (pairs.size() < 20) {
// 2) Simplify generic boolean CASE into AND/OR:
// CASE
// WHEN p1 THEN e1
// WHEN p2 THEN e2
// ELSE <else>
// END
// (p1 and e1) or (!p1 and p2 and e2) or (!p1 and !p2 and <else>)
// p1..pn not nullable
// if e1..en, <else> are TRUE/FALSE they may
// simplify the final epxression
// p1..pn being TRUE/FALSE were already eliminated by now by casePairs

// We start the NOT predicates with a TRUE
// It will be eliminated by simplification
// It has the role of an empty initial expression
boolean successAnyExpression = true;

RexNode notPredicates = rexBuilder.makeLiteral(true);
final List<RexNode> terms = new ArrayList<>();
for (Ord<Pair<RexNode, RexNode>> pair : Ord.zip(pairs)) {
if (pair.e.getKey().getType().isNullable()) {
successAnyExpression = false;
break;
}
final RexNode toAdd = RexUtil.composeConjunction(rexBuilder,
ImmutableList.<RexNode>of(
notPredicates,
pair.e.getKey(),
pair.e.getValue()),
false);
terms.add(toAdd);
// If the value is TRUE we can skip the key from the NOT list:
// p1 or (!p1 and p2) => p1 or p2
if (!pair.e.getValue().isAlwaysTrue()) {
notPredicates = RexUtil.composeConjunction(rexBuilder,
ImmutableList.<RexNode>of(
notPredicates,
RexUtil.not(pair.e.getKey())),
false);
notPredicates = simplify(notPredicates);
}
}
}
final List<RexNode> terms = new ArrayList<>();
final List<RexNode> notTerms = new ArrayList<>();
for (Ord<Pair<RexNode, RexNode>> pair : Ord.zip(pairs)) {
if (pair.e.getValue().isAlwaysTrue()) {
terms.add(RexUtil.andNot(rexBuilder, pair.e.getKey(), notTerms));
} else {
notTerms.add(pair.e.getKey());

if (successAnyExpression) {
final RexNode disjunction = simplify(RexUtil.composeDisjunction(rexBuilder, terms));
if (!call.getType().equals(disjunction.getType())) {
return rexBuilder.makeCast(call.getType(), disjunction);
}
return disjunction;
}
}
final RexNode disjunction = RexUtil.composeDisjunction(rexBuilder, terms);
if (!call.getType().equals(disjunction.getType())) {
return rexBuilder.makeCast(call.getType(), disjunction);
}
return disjunction;
}
if (newOperands.equals(operands)) {
return call;
}
return call.clone(call.getType(), newOperands);
}


/** Given "CASE WHEN p1 THEN v1 ... ELSE e END"
* returns [(p1, v1), ..., (true, e)]. */
private static List<Pair<RexNode, RexNode>> casePairs(RexBuilder rexBuilder,
Expand Down
152 changes: 149 additions & 3 deletions core/src/test/java/org/apache/calcite/test/RexProgramTest.java
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Expand Up @@ -1100,12 +1100,12 @@ private void checkExponentialCnf(int n) {

// case: remove false branches
checkSimplify(case_(eq(bRef, cRef), dRef, falseLiteral, aRef, eRef),
"CASE(=(?0.b, ?0.c), ?0.d, ?0.e)");
"OR(AND(=(?0.b, ?0.c), ?0.d), AND(<>(?0.b, ?0.c), ?0.e))");

// case: true branches become the last branch
checkSimplify(
case_(eq(bRef, cRef), dRef, trueLiteral, aRef, eq(cRef, dRef), eRef, cRef),
"CASE(=(?0.b, ?0.c), ?0.d, ?0.a)");
"OR(AND(=(?0.b, ?0.c), ?0.d), AND(<>(?0.b, ?0.c), ?0.a))");

// case: singleton
checkSimplify(case_(trueLiteral, aRef, eq(cRef, dRef), eRef, cRef), "?0.a");
Expand All @@ -1117,7 +1117,7 @@ private void checkExponentialCnf(int n) {
// case: trailing false and null, no simplification
checkSimplify2(
case_(aRef, trueLiteral, bRef, trueLiteral, cRef, falseLiteral, unknownLiteral),
"CASE(?0.a, true, ?0.b, true, ?0.c, false, null)",
"OR(?0.a, ?0.b, AND(null, NOT(?0.c)))",
"CAST(OR(?0.a, ?0.b)):BOOLEAN");

// case: form an AND of branches that return true
Expand Down Expand Up @@ -1318,6 +1318,152 @@ private void checkExponentialCnf(int n) {
assertThat(result, is(caseNode));
}

@Test public void testSimplifyCaseAsAndOr() throws Exception {
final RelDataType intType = typeFactory.createSqlType(SqlTypeName.INTEGER);
final RelDataType strType = typeFactory.createSqlType(SqlTypeName.VARCHAR, 255);
final RelDataType rowType = typeFactory.builder()
.add("i", intType)
.add("s", strType)
.build();

final RexDynamicParam range = rexBuilder.makeDynamicParam(rowType, 0);
final RexNode intRef = rexBuilder.makeFieldAccess(range, 0);
final RexNode strRef = rexBuilder.makeFieldAccess(range, 1);
final RexNode val3 = rexBuilder.makeLiteral(3, intType, false);
final RexNode val5 = rexBuilder.makeLiteral(5, intType, false);
final RexNode val7 = rexBuilder.makeLiteral(7, intType, false);
final RexNode val10 = rexBuilder.makeLiteral(10, intType, false);
final RexNode val11 = rexBuilder.makeLiteral(11, intType, false);
final RexNode val13 = rexBuilder.makeLiteral(13, intType, false);
final RexNode val25 = rexBuilder.makeLiteral(25, intType, false);
final RexNode val50 = rexBuilder.makeLiteral(50, intType, false);
final RexNode val100 = rexBuilder.makeLiteral(100, intType, false);
final RexNode val200 = rexBuilder.makeLiteral(200, intType, false);
final RexNode valFoo = rexBuilder.makeLiteral("foo");
final RexNode valBar = rexBuilder.makeLiteral("bar");
final RexNode valFar = rexBuilder.makeLiteral("far");
final RexNode valCar = rexBuilder.makeLiteral("car");

// CASE
// WHEN i = 3 THEN TRUE
// WHEN i = 5 THEN TRUE
// ELSE FALSE
// END
checkSimplifyFilter(
case_(
eq(intRef, val3), trueLiteral,
eq(intRef, val5), trueLiteral,
falseLiteral),
"OR(=(?0.i, 3), =(?0.i, 5))");

// CASE
// WHEN $1 = 3 THEN TRUE
// WHEN $1 = 5 THEN TRUE
// ELSE TRUE
// END
checkSimplifyFilter(
case_(
eq(intRef, val3), trueLiteral,
eq(intRef, val5), trueLiteral,
trueLiteral),
"true");

// CASE
// WHEN $1 = 3 THEN $2 = foo
// WHEN $1 = 5 THEN $2= bar
// ELSE TRUE
// END
checkSimplifyFilter(
case_(
eq(intRef, val3), eq(strRef, valFoo),
eq(intRef, val5), eq(strRef, valBar),
trueLiteral),
"OR("
+ "AND(=(?0.i, 3), =(?0.s, 'foo')), "
+ "AND(<>(?0.i, 3), =(?0.i, 5), =(?0.s, 'bar')), "
+ "AND(<>(?0.i, 3), <>(?0.i, 5)))");

// CASE
// WHEN $1 = 3 THEN $2 = foo
// WHEN $1 = 5 THEN $2= bar
// ELSE FALSE
// END
checkSimplifyFilter(
case_(
eq(intRef, val3), eq(strRef, valFoo),
eq(intRef, val5), eq(strRef, valBar),
falseLiteral),
"OR("
+ "AND(=(?0.i, 3), =(?0.s, 'foo')), "
+ "AND(<>(?0.i, 3), =(?0.i, 5), =(?0.s, 'bar')))");

// CASE
// WHEN $1 = 3 THEN $2 = foo
// WHEN $1 > 10 THEN
// CASE
// WHEN $i = 11 THEN $2 = bar
// WHEN $i = 13 THEN $2 = far
// ELSE ...
// WHEN $1 < 3 THEN $2 = car
// ELSE ...
// END
checkSimplifyFilter(
case_(
eq(intRef, val3), eq(strRef, valFoo),
gt(intRef, val10), case_(
eq(intRef, val11), eq(strRef, valBar),
eq(intRef, val13), eq(strRef, valFar),
falseLiteral),
lt(intRef, val3), eq(strRef, valCar),
trueLiteral),
"OR("
+ "AND(=(?0.i, 3), =(?0.s, 'foo')), "
+ "AND(<>(?0.i, 3), >(?0.i, 10), OR("
+ "AND(=(?0.i, 11), =(?0.s, 'bar')), "
+ "AND(<>(?0.i, 11), =(?0.i, 13), =(?0.s, 'far')))), "
+ "AND(<>(?0.i, 3), <(?0.i, 3), =(?0.s, 'car')), "
+ "AND(<>(?0.i, 3), <=(?0.i, 10), >=(?0.i, 3)))");

// CASE
// WHEN $1 = 3 THEN $2 = foo
// WHEN CASE
// WHEN $i >100 THEN $1 < 200
// WHEN $i < 50 THEN $1 > 25
// ELSE ...
// END THEN $2=bar
// WHEN $1 < 3 THEN $2 = car
// ELSE ...
// END
checkSimplifyFilter(
case_(
eq(intRef, val3), eq(strRef, valFoo),
case_(
gt(intRef, val100), lt(intRef, val200),
lt(intRef, val50), gt(intRef, val25),
trueLiteral), eq(strRef, valCar),
lt(intRef, val3), eq(strRef, valCar),
falseLiteral),
"OR("
+ "AND(=(?0.i, 3), =(?0.s, 'foo')),"
+ " AND(<>(?0.i, 3), OR("
+ "AND(>(?0.i, 100), <(?0.i, 200)),"
+ " AND(<=(?0.i, 100), <(?0.i, 50), >(?0.i, 25)),"
+ " AND(<=(?0.i, 100), >=(?0.i, 50))"
+ "), =(?0.s, 'car')),"
+ " AND(<>(?0.i, 3), OR("
+ "<=(?0.i, 100), "
+ ">=(?0.i, 200)"
+ "), OR("
+ ">(?0.i, 100), "
+ ">=(?0.i, 50), "
+ "<=(?0.i, 25)"
+ "), OR("
+ ">(?0.i, 100), "
+ "<(?0.i, 50)), "
+ "<(?0.i, 3), "
+ "=(?0.s, 'car')))");
}

@Test public void testSimplifyAnd() {
RelDataType booleanNotNullableType =
typeFactory.createTypeWithNullability(
Expand Down
8 changes: 4 additions & 4 deletions core/src/test/resources/org/apache/calcite/test/RelOptRulesTest.xml
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Expand Up @@ -27,7 +27,7 @@ where case when (sal = 1000) then
<Resource name="planAfter">
<![CDATA[
LogicalProject(SAL=[$5])
LogicalFilter(condition=[CASE(=($5, 1000), =($5, 1000), =($5, 2000))])
LogicalFilter(condition=[OR(=($5, 1000), AND(<>($5, 1000), =($5, 2000)))])
LogicalTableScan(table=[[CATALOG, SALES, EMP]])
]]>
</Resource>
Expand Down Expand Up @@ -5631,7 +5631,7 @@ LogicalAggregate(group=[{}], EXPR$0=[COUNT()])
<![CDATA[
LogicalAggregate(group=[{}], EXPR$0=[COUNT()])
LogicalProject($f0=[1])
LogicalFilter(condition=[=($7, 10)])
LogicalFilter(condition=[AND(<>($7, 20), =($7, 10))])
LogicalTableScan(table=[[CATALOG, SALES, EMP]])
]]>
</Resource>
Expand All @@ -5656,7 +5656,7 @@ LogicalAggregate(group=[{}], EXPR$0=[COUNT()])
<![CDATA[
LogicalAggregate(group=[{}], EXPR$0=[COUNT()])
LogicalProject($f0=[1])
LogicalFilter(condition=[=($7, 10)])
LogicalFilter(condition=[OR(AND(<>($7, 20), =($7, 10)), AND(<>($7, 20), null))])
LogicalTableScan(table=[[CATALOG, SALES, EMP]])
]]>
</Resource>
Expand All @@ -5683,7 +5683,7 @@ LogicalAggregate(group=[{}], EXPR$0=[COUNT()])
<![CDATA[
LogicalAggregate(group=[{}], EXPR$0=[COUNT()])
LogicalProject($f0=[1])
LogicalFilter(condition=[OR(=($7, 30), =($7, 10))])
LogicalFilter(condition=[OR(=($7, 30), AND(<>($7, 20), =($7, 10)))])
LogicalTableScan(table=[[CATALOG, SALES, EMP]])
]]>
</Resource>
Expand Down
2 changes: 1 addition & 1 deletion core/src/test/resources/org/apache/calcite/test/SqlToRelConverterTest.xml
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Expand Up @@ -1921,7 +1921,7 @@ from dept]]>
</Resource>
<Resource name="plan">
<![CDATA[
LogicalProject(NAME=[$1], EXPR$1=[CASE(=($2, 0), false, IS NOT NULL($6), true, <($3, $2), null, false)])
LogicalProject(NAME=[$1], EXPR$1=[OR(AND(<>($2, 0), IS NOT NULL($6)), AND(<>($2, 0), <($3, $2), null))])
LogicalJoin(condition=[=($4, $5)], joinType=[left])
LogicalProject($f0=[$0], $f1=[$1], $f2=[$2], $f3=[$3], $f4=[$0])
LogicalJoin(condition=[true], joinType=[inner])
Expand Down