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https://issues.apache.org/jira/browse/DRILL-4081?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15006133#comment-15006133
]
ASF GitHub Bot commented on DRILL-4081:
---------------------------------------
Github user jacques-n commented on a diff in the pull request:
https://github.com/apache/drill/pull/257#discussion_r44882947
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/UnionFunctions.java
---
@@ -32,16 +33,72 @@
import org.apache.drill.exec.expr.holders.UnionHolder;
import org.apache.drill.exec.expr.holders.IntHolder;
import org.apache.drill.exec.expr.holders.VarCharHolder;
+import org.apache.drill.exec.resolver.TypeCastRules;
import org.apache.drill.exec.vector.complex.impl.UnionReader;
import org.apache.drill.exec.vector.complex.reader.FieldReader;
import javax.inject.Inject;
+import java.util.Set;
/**
* The class contains additional functions for union types in addition to
those in GUnionFunctions
*/
public class UnionFunctions {
+ /**
+ * Returns zero if the inputs have equivalent types. Two numeric types
are considered equivalent, as are a combination
+ * of date/timestamp. If not equivalent, returns a value determined by
the numeric value of the MinorType enum
+ */
+ @FunctionTemplate(names = {"compareType"},
+ scope = FunctionTemplate.FunctionScope.SIMPLE,
+ nulls = NullHandling.INTERNAL)
+ public static class CompareType implements DrillSimpleFunc {
+
+ @Param
+ FieldReader input1;
+ @Param
+ FieldReader input2;
+ @Output
+ IntHolder out;
+
+ public void setup() {}
+
+ public void eval() {
+ org.apache.drill.common.types.TypeProtos.MinorType type1;
+ if (input1.isSet()) {
+ type1 = input1.getType().getMinorType();
+ } else {
+ type1 = org.apache.drill.common.types.TypeProtos.MinorType.NULL;
+ }
+ org.apache.drill.common.types.TypeProtos.MinorType type2;
+ if (input2.isSet()) {
+ type2 = input2.getType().getMinorType();
+ } else {
+ type2 = org.apache.drill.common.types.TypeProtos.MinorType.NULL;
+ }
+
+ out.value =
org.apache.drill.exec.expr.fn.impl.UnionFunctions.compareTypes(type1, type2);
+ }
+ }
+
+ public static int compareTypes(MinorType type1, MinorType type2) {
+ int typeValue1 = getTypeValue(type1);
+ int typeValue2 = getTypeValue(type2);
+ return typeValue1 - typeValue2;
+ }
+
+ private static int getTypeValue(MinorType type) {
+ if (TypeCastRules.isNumericType(type)) {
--- End diff --
would be good to add comments here.
> Handle schema changes in ExternalSort
> -------------------------------------
>
> Key: DRILL-4081
> URL: https://issues.apache.org/jira/browse/DRILL-4081
> Project: Apache Drill
> Issue Type: Improvement
> Reporter: Steven Phillips
> Assignee: Steven Phillips
>
> This improvement will make use of the Union vector to handle schema changes.
> When a new schema appears, the schema will be "merged" with the previous
> schema. The result will be a new schema that uses Union type to store the
> columns where this is a type conflict. All of the batches (including the
> batches that have already arrived) will be coerced into this new schema.
> A new comparison function will be included to handle the comparison of Union
> type. Comparison of union type will work as follows:
> 1. All numeric types can be mutually compared, and will be compared using
> Drill implicit cast rules.
> 2. All other types will not be compared against other types, but only among
> values of the same type.
> 3. There will be an overall precedence of types with regards to ordering.
> This precedence is not yet defined, but will be as part of the work on this
> issue.
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