Jay Narale created CALCITE-4994:
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Summary: SqlToRelConverter creates FieldMap for every Identifier
Instead of Memoizing it
Key: CALCITE-4994
URL: https://issues.apache.org/jira/browse/CALCITE-4994
Project: Calcite
Issue Type: Improvement
Components: core
Reporter: Jay Narale
When converting from Sql To Rel, In SqlToRelConverter for every single instance
of an identifier we create a new map in
*_org.apache.calcite.sql2rel.SqlToRelConverter.Blackboard#lookupExp_*
{code:java}
final Map<String, Integer> fieldOffsets = new HashMap<>();
for (RelDataTypeField f : resolve.rowType().getFieldList()) {
if (!fieldOffsets.containsKey(f.getName())) {
fieldOffsets.put(f.getName(), f.getIndex());
}
}
final Map<String, Integer> map = ImmutableMap.copyOf(fieldOffsets);{code}
So for a Sql Query
{code:java}
SELECT name, nation FROM customer{code}
We would do the above operation twice.
Memoization of this information will improve performance.
In my database, I had observed that for a large table involving 1200 columns
and a huge select having multiple expressions and operators, this part was a
bottleneck.
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