Skip to content

[SPARK-25714][SQL][followup] improve the comment inside BooleanSimplification rule #22711

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
cloud-fan wants to merge 2 commits into from
Closed

[SPARK-25714][SQL][followup] improve the comment inside BooleanSimplification rule #22711

Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
02e6100
improve the comment inside BooleanSimplification rule
cloud-fan Oct 13, 2018
21dab84
address comments
cloud-fan Oct 13, 2018
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
24 changes: 15 additions & 9 deletions sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -276,31 +276,37 @@ object BooleanSimplification extends Rule[LogicalPlan] with PredicateHelper {
case a And b if a.semanticEquals(b) => a
case a Or b if a.semanticEquals(b) => a

// The following optimization is applicable only when the operands are not nullable,
// The following optimizations are applicable only when the operands are not nullable,
// since the three-value logic of AND and OR are different in NULL handling.
// See the chart:
// +---------+---------+---------+---------+
// | p | q | p OR q | p AND q |
// | operand | operand | OR | AND |
Copy link
Contributor Author

@cloud-fan cloud-fan Oct 13, 2018

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

AND and OR is commutative, so we can reduce the entries in this table

// +---------+---------+---------+---------+
// | TRUE | TRUE | TRUE | TRUE |
// | TRUE | FALSE | TRUE | FALSE |
// | TRUE | UNKNOWN | TRUE | UNKNOWN |
// | FALSE | TRUE | TRUE | FALSE |
// | FALSE | FALSE | FALSE | FALSE |
// | FALSE | UNKNOWN | UNKNOWN | FALSE |
// | UNKNOWN | TRUE | TRUE | UNKNOWN |
// | UNKNOWN | FALSE | UNKNOWN | FALSE |
// | UNKNOWN | UNKNOWN | UNKNOWN | UNKNOWN |
// +---------+---------+---------+---------+

// This can break if a is null and c is false, so a can't be nullable.
Copy link
Contributor Author

@cloud-fan cloud-fan Oct 13, 2018

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

explain which input can break it, so it's easier to understand.

Copy link
Member

@gatorsmile gatorsmile Oct 13, 2018

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

The current code will not break. Thus, the comment is confusing to the future reader. To make it clear, we can just give the actual value.

(NULL And (NULL Or FALSE)) = NULL, but (NULL And FALSE) = FALSE. Thus, a can't be nullable.

case a And (b Or c) if !a.nullable && Not(a).semanticEquals(b) => And(a, c)
// This can break if a is null and b is false, so a can't be nullable.
case a And (b Or c) if !a.nullable && Not(a).semanticEquals(c) => And(a, b)
case (a Or b) And c if !a.nullable && a.semanticEquals(Not(c)) => And(b, c)
case (a Or b) And c if !b.nullable && b.semanticEquals(Not(c)) => And(a, c)
// This can break if c is null and b is false, so c can't be nullable.
case (a Or b) And c if !c.nullable && a.semanticEquals(Not(c)) => And(b, c)
Copy link
Contributor Author

@cloud-fan cloud-fan Oct 13, 2018

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

b.nullable and c.nullable are same, because a.semanticEquals(Not(c)).

// This can break if c is null and a is false, so c can't be nullable.
case (a Or b) And c if !c.nullable && b.semanticEquals(Not(c)) => And(a, c)

// This can break if a is null and c is true, so a can't be nullable.
case a Or (b And c) if !a.nullable && Not(a).semanticEquals(b) => Or(a, c)
// This can break if a is null and b is true, so a can't be nullable.
case a Or (b And c) if !a.nullable && Not(a).semanticEquals(c) => Or(a, b)
case (a And b) Or c if !a.nullable && a.semanticEquals(Not(c)) => Or(b, c)
case (a And b) Or c if !b.nullable && b.semanticEquals(Not(c)) => Or(a, c)
// This can break if c is null and b is true, so c can't be nullable.
case (a And b) Or c if !c.nullable && a.semanticEquals(Not(c)) => Or(b, c)
// This can break if c is null and a is true, so c can't be nullable.
case (a And b) Or c if !c.nullable && b.semanticEquals(Not(c)) => Or(a, c)

// Common factor elimination for conjunction
case and @ (left And right) =>
Expand Down