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https://issues.apache.org/jira/browse/SPARK-46071?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated SPARK-46071:
-----------------------------------
Labels: pull-request-available (was: )
> TreeNode.toJSON may result in OOM when there are multiple levels of nesting
> of expressions.
> -------------------------------------------------------------------------------------------
>
> Key: SPARK-46071
> URL: https://issues.apache.org/jira/browse/SPARK-46071
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 3.4.0
> Reporter: JacobZheng
> Priority: Major
> Labels: pull-request-available
>
> I am encountering an OOM exception when executing the following code:
> {code:scala}
> parser.parseExpression(sql).toJSON
> {code}
> This sql is a multiple nesting of {*}_CaseWhen_{*}. After testing I found
> that the number of expressions in the json increases exponentially as the
> number of nestings increases.
> Here are some example:
> sql:
> {code:sql}
> CASE WHEN(`cost` <= 275) THEN '(270-275]'
> ELSE '----' END
> {code}
> json:
> {code:json}
> [
> {
> "class":"org.apache.spark.sql.catalyst.expressions.CaseWhen",
> "num-children":3,
> "branches":[
> {
> "product-class":"scala.Tuple2",
> "_1":[
> {
>
> "class":"org.apache.spark.sql.catalyst.expressions.LessThanOrEqual",
> "num-children":2,
> "left":0,
> "right":1
> },
> {
>
> "class":"org.apache.spark.sql.catalyst.analysis.UnresolvedAttribute",
> "num-children":0,
> "nameParts":"[cost]"
> },
> {
>
> "class":"org.apache.spark.sql.catalyst.expressions.Literal",
> "num-children":0,
> "value":"275",
> "dataType":"integer"
> }
> ],
> "_2":[
> {
>
> "class":"org.apache.spark.sql.catalyst.expressions.Literal",
> "num-children":0,
> "value":"(270-275]",
> "dataType":"string"
> }
> ]
> }
> ],
> "elseValue":[
> {
> "class":"org.apache.spark.sql.catalyst.expressions.Literal",
> "num-children":0,
> "value":"----",
> "dataType":"string"
> }
> ]
> },
> {
> "class":"org.apache.spark.sql.catalyst.expressions.LessThanOrEqual",
> "num-children":2,
> "left":0,
> "right":1
> },
> {
> "class":"org.apache.spark.sql.catalyst.analysis.UnresolvedAttribute",
> "num-children":0,
> "nameParts":"[cost]"
> },
> {
> "class":"org.apache.spark.sql.catalyst.expressions.Literal",
> "num-children":0,
> "value":"275",
> "dataType":"integer"
> },
> {
> "class":"org.apache.spark.sql.catalyst.expressions.Literal",
> "num-children":0,
> "value":"(270-275]",
> "dataType":"string"
> },
> {
> "class":"org.apache.spark.sql.catalyst.expressions.Literal",
> "num-children":0,
> "value":"----",
> "dataType":"string"
> }
> ]
> {code}
> The child nodes of the *_CaseWhen_* expression are stored twice in JSON.
> When *_CaseWhen_* is nested twice, the child expression of the first case
> when is repeated 4 times, and so on.
> {code:sql}
> CASE WHEN(`cost` <= 270) THEN '(265-270]'
> ELSE
> CASE WHEN(`cost` <= 275) THEN '(270-275]'
> ELSE '----' END END
> {code}
> Nesting the *_CaseWhen_* expression n times in this case will result in
> 2^n+11 expressions in the json.
> The reason for this problem is that the field of *_CaseWhen_* cannot be
> converted to children index of when executing method {*}_jsonFields_{*}.
> Perhaps simplifying *_CaseWhen_* json a bit by overriding the *_jsonFields_*
> method is a viable way to go.
> {code:json}
> [
> {
> "class":"org.apache.spark.sql.catalyst.expressions.CaseWhen",
> "num-children":3,
> "branches":[
> {
> "condition":0,
> "value":1
> }
> ],
> "elseValue":2
> },
> {
> "class":"org.apache.spark.sql.catalyst.expressions.LessThanOrEqual",
> "num-children":2,
> "left":0,
> "right":1
> },
> {
> "class":"org.apache.spark.sql.catalyst.analysis.UnresolvedAttribute",
> "num-children":0,
> "nameParts":"[cost]"
> },
> {
> "class":"org.apache.spark.sql.catalyst.expressions.Literal",
> "num-children":0,
> "value":"275",
> "dataType":"integer"
> },
> {
> "class":"org.apache.spark.sql.catalyst.expressions.Literal",
> "num-children":0,
> "value":"(270-275]",
> "dataType":"string"
> },
> {
> "class":"org.apache.spark.sql.catalyst.expressions.Literal",
> "num-children":0,
> "value":"----",
> "dataType":"string"
> }
> ]
> {code}
>
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