Vladimir Sitnikov created CALCITE-3786:
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Summary: Add Digest (HashStrategy?) interface to enable efficient
hashCode/equals for RexNode, 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
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".
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
}
{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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