DonnyZone commented on a change in pull request #1347: [CALCITE-3224] New
RexNode-to-Expression CodeGen Implementation
URL: https://github.com/apache/calcite/pull/1347#discussion_r355250676
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File path: core/src/test/java/org/apache/calcite/test/JdbcTest.java
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@@ -2451,12 +2451,14 @@ private void
checkNullableTimestamp(CalciteAssert.Config config) {
CalciteAssert.hr()
.query(
"select upper((case when \"empid\">\"deptno\"*10 then 'y' else
null end)) T from \"hr\".\"emps\"")
- .planContains("static final String "
- + "$L4J$C$org_apache_calcite_runtime_SqlFunctions_upper_y_ = "
- + "org.apache.calcite.runtime.SqlFunctions.upper(\"y\");")
- .planContains("return current.empid <= current.deptno * 10 "
- + "? (String) null "
- + ": $L4J$C$org_apache_calcite_runtime_SqlFunctions_upper_y_;")
+ .planContains(" String case_when_value;\n"
Review comment:
The new codegen framework can naturally reuses expressions, due to:
It removes the mutable state (i.e., `Map<? extends RexNode, Boolean>
exprNullableMap`), and generates code strictly corresonding to RexNode in
one-to-one manner.
Therefore, the redundant code (including `null` checking) caused by
tranversing with mutable state will not be produced again in the new codegen.
On the other hand, we also keep a map in `RexToLixTranslator` for same
RexNode's code reuse.
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