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Posted to reviews@spark.apache.org by GitBox <gi...@apache.org> on 2022/02/09 14:57:52 UTC
[GitHub] [spark] Dooyoung-Hwang opened a new pull request #35465: [SPARK-38168][SQL] LikeSimplification rule handles escape characters
Dooyoung-Hwang opened a new pull request #35465:
URL: https://github.com/apache/spark/pull/35465
### What changes were proposed in this pull request?
Currently, LikeSimplification rule is skipped if the pattern in LIKE filter contains an escape character.
Thus, the filter "LIKE '%100\\%'" in this query is not optimized into 'EndsWith' of StringType.
```
spark.sql("SELECT * FROM tbl LIKE '%100\\%'").explain(true)
...
== Optimized Logical Plan ==
Filter (isnotnull(c_1#0) && c_1#0 LIKE %100\%)
+- Relation[c_1#0,c_2#1,c_3#2]
...
```
LikeSimplification rule can consider a special character(wildcard(%, _) or escape character) as a plain character if the special character follows an escape character. By doing that, LikeSimplification rule can optimize the filter like below.
```
spark.sql("SELECT * FROM tbl LIKE '%100\\%'").explain(true)
...
== Optimized Logical Plan ==
Filter (isnotnull(c_1#0) && EndsWith(c_1#0, 100%))
+- Relation[c_1#0,c_2#1,c_3#2]
```
### Why are the changes needed?
To enhance performance of processing LIKE filters such as "LIKE '%100\\%'", "LIKE '\\%100\\%'", "LIKE '%\\%100\\%%'", "LIKE '100\\%%'", "LIKE '100\\%%90\\%'"
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
Test suites are added in LikeSimplificationSuite.
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[GitHub] [spark] AmplabJenkins commented on pull request #35465: [SPARK-38168][SQL] LikeSimplification rule handles escape characters
Posted by GitBox <gi...@apache.org>.
AmplabJenkins commented on pull request #35465:
URL: https://github.com/apache/spark/pull/35465#issuecomment-1034512588
Can one of the admins verify this patch?
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[GitHub] [spark] cloud-fan commented on a change in pull request #35465: [SPARK-38168][SQL] LikeSimplification rule handles escape characters
Posted by GitBox <gi...@apache.org>.
cloud-fan commented on a change in pull request #35465:
URL: https://github.com/apache/spark/pull/35465#discussion_r803309117
##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
##########
@@ -680,42 +680,50 @@ object PushFoldableIntoBranches extends Rule[LogicalPlan] with PredicateHelper {
* pattern.
*/
object LikeSimplification extends Rule[LogicalPlan] {
- // if guards below protect from escapes on trailing %.
- // Cases like "something\%" are not optimized, but this does not affect correctness.
- private val startsWith = "([^_%]+)%".r
- private val endsWith = "%([^_%]+)".r
- private val startsAndEndsWith = "([^_%]+)%([^_%]+)".r
- private val contains = "%([^_%]+)%".r
- private val equalTo = "([^_%]*)".r
-
private def simplifyLike(
input: Expression, pattern: String, escapeChar: Char = '\\'): Option[Expression] = {
- if (pattern.contains(escapeChar)) {
- // There are three different situations when pattern containing escapeChar:
- // 1. pattern contains invalid escape sequence, e.g. 'm\aca'
- // 2. pattern contains escaped wildcard character, e.g. 'ma\%ca'
- // 3. pattern contains escaped escape character, e.g. 'ma\\ca'
- // Although there are patterns can be optimized if we handle the escape first, we just
- // skip this rule if pattern contains any escapeChar for simplicity.
Review comment:
This is a trade-off between code simplicity and performance. The assumption is that using escape char is rare and we shouldn't add a complicated implementation for it.
Besides, Spark now provides `starts_with`, `ends_with`, etc. functions and people can use them directly.
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[GitHub] [spark] Dooyoung-Hwang commented on a change in pull request #35465: [SPARK-38168][SQL] LikeSimplification rule handles escape characters
Posted by GitBox <gi...@apache.org>.
Dooyoung-Hwang commented on a change in pull request #35465:
URL: https://github.com/apache/spark/pull/35465#discussion_r803313544
##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
##########
@@ -680,42 +680,50 @@ object PushFoldableIntoBranches extends Rule[LogicalPlan] with PredicateHelper {
* pattern.
*/
object LikeSimplification extends Rule[LogicalPlan] {
- // if guards below protect from escapes on trailing %.
- // Cases like "something\%" are not optimized, but this does not affect correctness.
- private val startsWith = "([^_%]+)%".r
- private val endsWith = "%([^_%]+)".r
- private val startsAndEndsWith = "([^_%]+)%([^_%]+)".r
- private val contains = "%([^_%]+)%".r
- private val equalTo = "([^_%]*)".r
-
private def simplifyLike(
input: Expression, pattern: String, escapeChar: Char = '\\'): Option[Expression] = {
- if (pattern.contains(escapeChar)) {
- // There are three different situations when pattern containing escapeChar:
- // 1. pattern contains invalid escape sequence, e.g. 'm\aca'
- // 2. pattern contains escaped wildcard character, e.g. 'ma\%ca'
- // 3. pattern contains escaped escape character, e.g. 'ma\\ca'
- // Although there are patterns can be optimized if we handle the escape first, we just
- // skip this rule if pattern contains any escapeChar for simplicity.
Review comment:
Ok, thank you.
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[GitHub] [spark] Dooyoung-Hwang commented on pull request #35465: [SPARK-38168][SQL] LikeSimplification rule handles escape characters
Posted by GitBox <gi...@apache.org>.
Dooyoung-Hwang commented on pull request #35465:
URL: https://github.com/apache/spark/pull/35465#issuecomment-1033858911
Could you review this patch?
@cloud-fan @HyukjinKwon @dongjoon-hyun
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[GitHub] [spark] Dooyoung-Hwang closed pull request #35465: [SPARK-38168][SQL] LikeSimplification rule handles escape characters
Posted by GitBox <gi...@apache.org>.
Dooyoung-Hwang closed pull request #35465:
URL: https://github.com/apache/spark/pull/35465
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