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SQL: Fix issue with folding of CASE/IIF
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Add extra checks to prevent ConstantFolding rule to try to fold
the CASE/IIF functions early before the SimplifyCase rule gets applied.

Fixes: elastic#49387
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@matriv
matriv committed Nov 21, 2019
1 parent 4db330d commit 895f331
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Showing 2 changed files with 78 additions and 7 deletions.
14 changes: 12 additions & 2 deletions .../sql/src/main/java/org/elasticsearch/xpack/sql/expression/predicate/conditional/Case.java
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Original file line number Diff line number Diff line change
Expand Up @@ -120,8 +120,18 @@ protected TypeResolution resolveType() {
*/
@Override
public boolean foldable() {
return (conditions.isEmpty() && elseResult.foldable()) ||
(conditions.size() == 1 && conditions.get(0).condition().foldable() && conditions.get(0).result().foldable());
if (conditions.isEmpty() && elseResult.foldable()) {
return true;
}
if (conditions.size() == 1 && conditions.get(0).condition().foldable()) {
// Need to prevent ConstantFolding rule to get applied before SimplifyCase rule
if (conditions.get(0).condition().fold() == Boolean.TRUE) {
return conditions().get(0).result().foldable();
} else {
return elseResult().foldable();
}
}
return false;
}

@Override
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71 changes: 66 additions & 5 deletions x-pack/plugin/sql/src/test/java/org/elasticsearch/xpack/sql/optimizer/OptimizerTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -671,6 +671,8 @@ public void testSimplifyCaseConditionsFoldWhenFalse() {
new IfConditional(EMPTY, new Equals(EMPTY, TWO, ONE), Literal.of(EMPTY, "bar2")),
new IfConditional(EMPTY, new GreaterThan(EMPTY, getFieldAttribute(), ONE), Literal.of(EMPTY, "foo2")),
Literal.of(EMPTY, "default")));
assertFalse(c.foldable());

Expression e = new SimplifyCase().rule(c);
assertEquals(Case.class, e.getClass());
c = (Case) e;
Expand All @@ -696,13 +698,15 @@ public void testSimplifyCaseConditionsFoldWhenTrue() {
// ELSE 'default'
// END

SimplifyCase rule = new SimplifyCase();
Case c = new Case(EMPTY, Arrays.asList(
new IfConditional(EMPTY, new Equals(EMPTY, getFieldAttribute(), ONE), Literal.of(EMPTY, "foo1")),
new IfConditional(EMPTY, new Equals(EMPTY, ONE, ONE), Literal.of(EMPTY, "bar1")),
new IfConditional(EMPTY, new Equals(EMPTY, TWO, ONE), Literal.of(EMPTY, "bar2")),
new IfConditional(EMPTY, new GreaterThan(EMPTY, getFieldAttribute(), ONE), Literal.of(EMPTY, "foo2")),
Literal.of(EMPTY, "default")));
assertFalse(c.foldable());

SimplifyCase rule = new SimplifyCase();
Expression e = rule.rule(c);
assertEquals(Case.class, e.getClass());
c = (Case) e;
Expand All @@ -713,7 +717,7 @@ public void testSimplifyCaseConditionsFoldWhenTrue() {
assertEquals(TypeResolution.TYPE_RESOLVED, c.typeResolved());
}

public void testSimplifyCaseConditionsFoldCompletely() {
public void testSimplifyCaseConditionsFoldCompletely_FoldableElse() {
// CASE WHEN 1 = 2 THEN 'foo1'
// WHEN 1 = 1 THEN 'foo2'
// ELSE 'default'
Expand All @@ -723,11 +727,13 @@ public void testSimplifyCaseConditionsFoldCompletely() {
//
// 'foo2'

SimplifyCase rule = new SimplifyCase();
Case c = new Case(EMPTY, Arrays.asList(
new IfConditional(EMPTY, new Equals(EMPTY, ONE, TWO), Literal.of(EMPTY, "foo1")),
new IfConditional(EMPTY, new Equals(EMPTY, ONE, ONE), Literal.of(EMPTY, "foo2")),
Literal.of(EMPTY, "default")));
assertFalse(c.foldable());

SimplifyCase rule = new SimplifyCase();
Expression e = rule.rule(c);
assertEquals(Case.class, e.getClass());
c = (Case) e;
Expand All @@ -738,9 +744,34 @@ public void testSimplifyCaseConditionsFoldCompletely() {
assertEquals(TypeResolution.TYPE_RESOLVED, c.typeResolved());
}

public void testSimplifyIif_ConditionTrue() {
public void testSimplifyCaseConditionsFoldCompletely_NonFoldableElse() {
// CASE WHEN 1 = 2 THEN 'foo1'
// ELSE myField
// END
//
// ==>
//
// myField (non-foldable)

Case c = new Case(EMPTY, Arrays.asList(
new IfConditional(EMPTY, new Equals(EMPTY, ONE, TWO), Literal.of(EMPTY, "foo1")),
getFieldAttribute("myField")));
assertFalse(c.foldable());

SimplifyCase rule = new SimplifyCase();
Expression e = rule.rule(c);
assertEquals(Case.class, e.getClass());
c = (Case) e;
assertEquals(0, c.conditions().size());
assertFalse(c.foldable());
assertEquals("myField", Expressions.name(c.elseResult()));
}

public void testSimplifyIif_ConditionTrue_FoldableResult() {
SimplifyCase rule = new SimplifyCase();
Iif iif = new Iif(EMPTY, new Equals(EMPTY, ONE, ONE), Literal.of(EMPTY, "foo"), Literal.of(EMPTY, "bar"));
assertTrue(iif.foldable());

Expression e = rule.rule(iif);
assertEquals(Iif.class, e.getClass());
iif = (Iif) e;
Expand All @@ -750,9 +781,26 @@ public void testSimplifyIif_ConditionTrue() {
assertEquals(TypeResolution.TYPE_RESOLVED, iif.typeResolved());
}

public void testSimplifyIif_ConditionFalse() {
public void testSimplifyIif_ConditionTrue_NonFoldableResult() {
SimplifyCase rule = new SimplifyCase();
Iif iif = new Iif(EMPTY, new Equals(EMPTY, ONE, ONE), getFieldAttribute("myField"), Literal.of(EMPTY, "bar"));
assertFalse(iif.foldable());

Expression e = rule.rule(iif);
assertEquals(Iif.class, e.getClass());
iif = (Iif) e;
assertEquals(1, iif.conditions().size());
assertFalse(iif.foldable());
assertTrue(iif.conditions().get(0).condition().foldable());
assertEquals(Boolean.TRUE, iif.conditions().get(0).condition().fold());
assertEquals("myField", Expressions.name(iif.conditions().get(0).result()));
}

public void testSimplifyIif_ConditionFalse_FoldableResult() {
SimplifyCase rule = new SimplifyCase();
Iif iif = new Iif(EMPTY, new Equals(EMPTY, ONE, TWO), Literal.of(EMPTY, "foo"), Literal.of(EMPTY, "bar"));
assertTrue(iif.foldable());

Expression e = rule.rule(iif);
assertEquals(Iif.class, e.getClass());
iif = (Iif) e;
Expand All @@ -762,6 +810,19 @@ public void testSimplifyIif_ConditionFalse() {
assertEquals(TypeResolution.TYPE_RESOLVED, iif.typeResolved());
}

public void testSimplifyIif_ConditionFalse_NonFoldableResult() {
SimplifyCase rule = new SimplifyCase();
Iif iif = new Iif(EMPTY, new Equals(EMPTY, ONE, TWO), Literal.of(EMPTY, "foo"), getFieldAttribute("myField"));
assertFalse(iif.foldable());

Expression e = rule.rule(iif);
assertEquals(Iif.class, e.getClass());
iif = (Iif) e;
assertEquals(0, iif.conditions().size());
assertFalse(iif.foldable());
assertEquals("myField", Expressions.name(iif.elseResult()));
}

//
// Logical simplifications
//
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