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https://issues.apache.org/jira/browse/CALCITE-3786?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Danny Chen resolved CALCITE-3786.
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Fix Version/s: 1.24.0
Resolution: Fixed
Fixed in
[2039685|https://github.com/apache/calcite/pull/2016/commits/2039685a7280cf647f194fca9784ae9879560d19]
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> Add Digest interface to enable efficient hashCode(equals) for RexNode and
> RelNode
> ---------------------------------------------------------------------------------
>
> Key: CALCITE-3786
> URL: https://issues.apache.org/jira/browse/CALCITE-3786
> Project: Calcite
> Issue Type: New Feature
> Components: core
> Affects Versions: 1.21.0
> Reporter: Vladimir Sitnikov
> Assignee: Danny Chen
> Priority: Major
> Fix For: 1.24.0
>
> Time Spent: 3h 10m
> Remaining Estimate: 0h
>
> Current digests for RexNode, RelNode, RelType, and similar cases use String
> concatenation.
> It is easy to implement, however, it has drawbacks:
> 1) String objects cannot be reused. For instance, RexCall has operands,
> however, the digest is duplicated. It causes extra memory use and extra CPU
> for string copying
> 2) There's no way to have multiple #toString() methods. RelType might need
> multiple digests: "including field names", "excluding field names".
> A suggested resolution might be behind the lines of
> {code:java}
> class Digest { // immutable
> final int hashCode; // speedup hashCode and equals
> final Object[] contents; // The values are either other Digest objects or
> Strings
> String toString(); // e.g. for debugging purposes
> int compareTo(Digest); // e.g. for debugging purposes.
> }
> {code}
> Note how fields in Kotlin are aligned much better, and it makes it easier to
> read:
> {code:java}
> class Digest { // immutable
> val hashCode: Int // speedup hashCode and equals
> val contents: Array<Any> // The values are either other Digest objects or
> Strings
> fun toString(): String // e.g. for debugging purposes
> fun compareTo(other: Digest): Int // e.g. for debugging purposes.
> }
> {code}
> Then the digest for RexCall could be the bits relevant to RexCall itself +
> digests of the operands (which can be reused as is)
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