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[GitHub] [spark] vitaliili-db opened a new pull request, #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
vitaliili-db opened a new pull request, #37631:
URL: https://github.com/apache/spark/pull/37631
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Special case for `split` function when `regex` parameter is empty. The result will split input string but avoid empty remainder/tail string. I.e. `split('hello', '')` will produce `['h', 'e', 'l', 'l', 'o']` instead of `['h', 'e', 'l', 'l', 'o', '']`. Old behavior is preserved when `limit` parameter is explicitly set to negative value - `split('hello', '', -1)`
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This is nice to have and matches intuitively expected behavior.
### Does this PR introduce _any_ user-facing change?
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Yes.
- `split` function output changes when empty `regex` parameter is provided and `limit` parameter is not specified or set to 0. In this case a trailing empty string is ignored.
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Unit tests.
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[GitHub] [spark] cloud-fan commented on a diff in pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
Posted by GitBox <gi...@apache.org>.
cloud-fan commented on code in PR #37631:
URL: https://github.com/apache/spark/pull/37631#discussion_r954000072
##########
docs/sql-migration-guide.md:
##########
@@ -28,6 +28,7 @@ license: |
- Since Spark 3.4, v1 database, table, permanent view and function identifier will include 'spark_catalog' as the catalog name if database is defined, e.g. a table identifier will be: `spark_catalog.default.t`. To restore the legacy behavior, set `spark.sql.legacy.v1IdentifierNoCatalog` to `true`.
- Since Spark 3.4, when ANSI SQL mode(configuration `spark.sql.ansi.enabled`) is on, Spark SQL always returns NULL result on getting a map value with a non-existing key. In Spark 3.3 or earlier, there will be an error.
- Since Spark 3.4, the SQL CLI `spark-sql` does not print the prefix `Error in query:` before the error message of `AnalysisException`.
+ - Since Spark 3.4, `split` function ignores trailing empty strings when `regex` parameter is empty and `limit` parameter is not specified or set to 0 or -1.
Review Comment:
```suggestion
- Since Spark 3.4, `split` function ignores trailing empty strings when `regex` parameter is empty and `limit` parameter is not specified or set to a non-positive number.
```
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[GitHub] [spark] vitaliili-db commented on pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
Posted by GitBox <gi...@apache.org>.
vitaliili-db commented on PR #37631:
URL: https://github.com/apache/spark/pull/37631#issuecomment-1230981751
@cloud-fan thank you, that is a great suggestion. Done.
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[GitHub] [spark] vitaliili-db commented on a diff in pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
Posted by GitBox <gi...@apache.org>.
vitaliili-db commented on code in PR #37631:
URL: https://github.com/apache/spark/pull/37631#discussion_r953973254
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/regexpExpressions.scala:
##########
@@ -527,7 +527,7 @@ case class StringSplit(str: Expression, regex: Expression, limit: Expression)
override def second: Expression = regex
override def third: Expression = limit
- def this(exp: Expression, regex: Expression) = this(exp, regex, Literal(-1));
+ def this(exp: Expression, regex: Expression) = this(exp, regex, Literal(0))
Review Comment:
Yes, you are correct. This should not change. Reverted.
##########
common/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java:
##########
@@ -1000,6 +1000,17 @@ public static UTF8String concatWs(UTF8String separator, UTF8String... inputs) {
}
public UTF8String[] split(UTF8String pattern, int limit) {
+ // This is a special case for converting string into array of symbols without a trailing empty
+ // string. E.g. `"hello".split("", 0) => ["h", "e", "l", "l", "o"].
+ // Note that negative limit will preserve a trailing empty string.
+ if (limit == 0 && numBytes() != 0 && pattern.numBytes() == 0) {
+ byte[] input = getBytes();
+ UTF8String[] result = new UTF8String[numBytes];
+ for (int i = 0; i < numBytes; i++) {
Review Comment:
Great catch, fixed!
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[GitHub] [spark] cloud-fan commented on a diff in pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
Posted by GitBox <gi...@apache.org>.
cloud-fan commented on code in PR #37631:
URL: https://github.com/apache/spark/pull/37631#discussion_r953400215
##########
common/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java:
##########
@@ -1000,6 +1000,17 @@ public static UTF8String concatWs(UTF8String separator, UTF8String... inputs) {
}
public UTF8String[] split(UTF8String pattern, int limit) {
+ // This is a special case for converting string into array of symbols without a trailing empty
+ // string. E.g. `"hello".split("", 0) => ["h", "e", "l", "l", "o"].
+ // Note that negative limit will preserve a trailing empty string.
+ if (limit == 0 && numBytes() != 0 && pattern.numBytes() == 0) {
+ byte[] input = getBytes();
+ UTF8String[] result = new UTF8String[numBytes];
+ for (int i = 0; i < numBytes; i++) {
Review Comment:
are we sure it's one byte per character?
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[GitHub] [spark] vitaliili-db commented on pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
Posted by GitBox <gi...@apache.org>.
vitaliili-db commented on PR #37631:
URL: https://github.com/apache/spark/pull/37631#issuecomment-1224996770
@cloud-fan
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[GitHub] [spark] cloud-fan commented on pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
Posted by GitBox <gi...@apache.org>.
cloud-fan commented on PR #37631:
URL: https://github.com/apache/spark/pull/37631#issuecomment-1229682384
ah, now I understand where the trailing empty string comes from, thanks! I agree to go with the "split and drop trailing empty string" behavior, but can we do it regardless of the limit parameter? I'd expect something like
```
if (split == "") {
str.toSeq.take(limit)
}
```
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[GitHub] [spark] cloud-fan commented on pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
Posted by GitBox <gi...@apache.org>.
cloud-fan commented on PR #37631:
URL: https://github.com/apache/spark/pull/37631#issuecomment-1226707879
This seems a bit inconsistent. According to the function doc, `-1` means no limit, and it's confusing why no limit is different from a large enough limit (which means no limit as well).
I'd consider trailing empty string as a bug, can we fix it in all the cases?
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[GitHub] [spark] vitaliili-db commented on a diff in pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
Posted by GitBox <gi...@apache.org>.
vitaliili-db commented on code in PR #37631:
URL: https://github.com/apache/spark/pull/37631#discussion_r958704810
##########
common/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java:
##########
@@ -1000,6 +1000,22 @@ public static UTF8String concatWs(UTF8String separator, UTF8String... inputs) {
}
public UTF8String[] split(UTF8String pattern, int limit) {
+ // This is a special case for converting string into array of symbols without a trailing empty
+ // string. E.g. `"hello".split("", 0) => ["h", "e", "l", "l", "o"].
+ // Note that negative limit will preserve a trailing empty string.
Review Comment:
Done, thank you for reviewing!
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[GitHub] [spark] vitaliili-db commented on pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
Posted by GitBox <gi...@apache.org>.
vitaliili-db commented on PR #37631:
URL: https://github.com/apache/spark/pull/37631#issuecomment-1228950512
@cloud-fan trailing empty string is not actually a bug, it has consistent behavior in all systems, e.g. `split("aaAbbAccA", "A")` gives same result in all systems => `['aa', 'bb', 'cc', '']`. So were are pretty consistent here. The only difference in absence of `limit` parameter (e.g. for migration purposes) is how empty delimiter/regex behaves. As mentioned we might choose either ignore regex (return original string), split and drop trailing empty string (this PR) or do nothing and return array with trailing empty string.
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[GitHub] [spark] cloud-fan commented on pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
Posted by GitBox <gi...@apache.org>.
cloud-fan commented on PR #37631:
URL: https://github.com/apache/spark/pull/37631#issuecomment-1225936870
What should be the behavior of `split('hello', '', 100)`? Do other databases return a trailing empty string?
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[GitHub] [spark] AmplabJenkins commented on pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
Posted by GitBox <gi...@apache.org>.
AmplabJenkins commented on PR #37631:
URL: https://github.com/apache/spark/pull/37631#issuecomment-1225920329
Can one of the admins verify this patch?
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[GitHub] [spark] vitaliili-db commented on pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
Posted by GitBox <gi...@apache.org>.
vitaliili-db commented on PR #37631:
URL: https://github.com/apache/spark/pull/37631#issuecomment-1226095179
@cloud-fan other databases don't have `limit` parameter in `split` function. In addition a second parameter is a string in other systems as opposed to regex in Spark. Closest method we have is `StringSplitSQL` but we cannot replace it since it will be bigger breaking change for users who use `limit` parameter.
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[GitHub] [spark] cloud-fan commented on a diff in pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
Posted by GitBox <gi...@apache.org>.
cloud-fan commented on code in PR #37631:
URL: https://github.com/apache/spark/pull/37631#discussion_r957940422
##########
common/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java:
##########
@@ -1000,6 +1000,22 @@ public static UTF8String concatWs(UTF8String separator, UTF8String... inputs) {
}
public UTF8String[] split(UTF8String pattern, int limit) {
+ // This is a special case for converting string into array of symbols without a trailing empty
+ // string. E.g. `"hello".split("", 0) => ["h", "e", "l", "l", "o"].
+ // Note that negative limit will preserve a trailing empty string.
Review Comment:
We need to update this comment now.
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[GitHub] [spark] cloud-fan closed pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
Posted by GitBox <gi...@apache.org>.
cloud-fan closed pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
URL: https://github.com/apache/spark/pull/37631
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[GitHub] [spark] cloud-fan commented on pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
Posted by GitBox <gi...@apache.org>.
cloud-fan commented on PR #37631:
URL: https://github.com/apache/spark/pull/37631#issuecomment-1232655094
thanks, merging to master!
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[GitHub] [spark] cloud-fan commented on a diff in pull request #37631: [SPARK-40194][SQL] SPLIT function on empty regex should truncate trailing empty string.
Posted by GitBox <gi...@apache.org>.
cloud-fan commented on code in PR #37631:
URL: https://github.com/apache/spark/pull/37631#discussion_r953401126
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/regexpExpressions.scala:
##########
@@ -527,7 +527,7 @@ case class StringSplit(str: Expression, regex: Expression, limit: Expression)
override def second: Expression = regex
override def third: Expression = limit
- def this(exp: Expression, regex: Expression) = this(exp, regex, Literal(-1));
+ def this(exp: Expression, regex: Expression) = this(exp, regex, Literal(0))
Review Comment:
ideally 0 and -1 should be no difference according to the function doc. Do you use -1 as a legacy flag?
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