Github user kaspersorensen commented on a diff in the pull request:
https://github.com/apache/metamodel/pull/34#discussion_r36036345
--- Diff: core/src/main/java/org/apache/metamodel/query/FunctionType.java
---
@@ -18,105 +18,22 @@
*/
package org.apache.metamodel.query;
-import org.apache.metamodel.schema.Column;
-import org.apache.metamodel.schema.ColumnType;
import org.apache.metamodel.util.AggregateBuilder;
/**
- * Represents an aggregate function to use in a SelectItem.
- *
+ * Represents a generic function to use in a SelectItem.
+ *
* @see SelectItem
- */
-public enum FunctionType {
-
- COUNT {
- @Override
- public AggregateBuilder<Long> build() {
- return new CountAggregateBuilder();
- }
- },
- AVG {
- @Override
- public AggregateBuilder<Double> build() {
- return new AverageAggregateBuilder();
- }
- },
- SUM {
- @Override
- public AggregateBuilder<Double> build() {
- return new SumAggregateBuilder();
- }
- },
- MAX {
- @Override
- public AggregateBuilder<Object> build() {
- return new MaxAggregateBuilder();
- }
- },
- MIN {
- @Override
- public AggregateBuilder<Object> build() {
- return new MinAggregateBuilder();
- }
- };
-
- public ColumnType getExpectedColumnType(ColumnType type) {
- switch (this) {
- case COUNT:
- return ColumnType.BIGINT;
- case AVG:
- case SUM:
- return ColumnType.DOUBLE;
- case MAX:
- case MIN:
- return type;
- default:
- return type;
- }
- }
-
- public SelectItem createSelectItem(Column column) {
- return new SelectItem(this, column);
- }
-
- public SelectItem createSelectItem(String expression, String alias) {
- return new SelectItem(this, expression, alias);
- }
-
- public Object evaluate(Iterable<?> values) {
- AggregateBuilder<?> builder = build();
- for (Object object : values) {
- builder.add(object);
- }
- return builder.getAggregate();
- }
+*/
+public interface FunctionType extends Function {
- /**
- * Executes the function
- *
- * @param values
- * the values to be evaluated. If a value is null it won't
be
- * evaluated
- * @return the result of the function execution. The return type class
is
- * dependent on the FunctionType and the values provided. COUNT
- * yields a Long, AVG and SUM yields Double values and MAX and
MIN
- * yields the type of the provided values.
- */
- public Object evaluate(Object... values) {
- AggregateBuilder<?> builder = build();
- for (Object object : values) {
- builder.add(object);
- }
- return builder.getAggregate();
- }
+ public static final AggregateFunction COUNT = new
CountAggregateFunction();
+ public static final AggregateFunction AVG = new
AverageAggregateFunction();
+ public static final AggregateFunction SUM = new SumAggregateFunction();
+ public static final AggregateFunction MAX = new MaxAggregateFunction();
+ public static final AggregateFunction MIN = new MinAggregateFunction();
- public abstract AggregateBuilder<?> build();
+ public AggregateBuilder<?> build();
--- End diff --
I think this method is implementation oriented and should maybe then be
kept out of the interface. Or else the evaluate method should - they kinda
serve the same purpose.
And they are both aggregation function oriented so none of them should be
here but if anywhere in the AggregateFunction interface.
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