[Kernel] Remove unused ExpressionHandler.isSupported(...) for now (d…

…elta-io#3018)

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#### Which Delta project/connector is this regarding?
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- [ ] Spark
- [ ] Standalone
- [ ] Flink
- [X] Kernel
- [ ] Other (fill in here)

## Description

Removes a currently unused API in `ExpressionHandler`.

See delta-io#3017 for details. **TLDR**
we added this API before achieving consensus on what we want to
implement and it is currently unused. Remove it for now and we can add
it back later if needed.

## How was this patch tested?

N/A

## Does this PR introduce _any_ user-facing changes?

No

kernel/kernel-api/src/main/java/io/delta/kernel/engine/ExpressionHandler.java

@@ -34,15 +34,6 @@
  */
 @Evolving
 public interface ExpressionHandler {
-    /**
-     * Is the given expression evaluation supported on the data with given schema?
-     *
-     * @param inputSchema Schema of input data on which the expression is evaluated.
-     * @param expression Expression to check whether it is supported for evaluation.
-     * @param outputType Expected result data type.
-     * @return true if supported and false otherwise.
-     */
-    boolean isSupported(StructType inputSchema, Expression expression, DataType outputType);
 
     /**
      * Create an {@link ExpressionEvaluator} that can evaluate the given <i>expression</i> on

kernel/kernel-api/src/test/scala/io/delta/kernel/test/MockEngineUtils.scala

@@ -136,12 +136,6 @@ trait BaseMockExpressionHandler extends ExpressionHandler {
       outputType: DataType): ExpressionEvaluator =
     throw new UnsupportedOperationException("not supported in this test suite")
 
-  override def isSupported(
-      inputSchema: StructType,
-      expression: Expression,
-      outputType: DataType): Boolean =
-    throw new UnsupportedOperationException("not supported in this test suite")
-
   override def createSelectionVector(values: Array[Boolean], from: Int, to: Int): ColumnVector =
     throw new UnsupportedOperationException("not supported in this test suite")
 }

kernel/kernel-defaults/src/main/java/io/delta/kernel/defaults/engine/DefaultExpressionHandler.java

@@ -38,17 +38,6 @@
  * Default implementation of {@link ExpressionHandler}
  */
 public class DefaultExpressionHandler implements ExpressionHandler {
-    @Override
-    public boolean isSupported(StructType inputSchema, Expression expression, DataType outputType) {
-        // There is no extra cost to create an expression handler in default implementation in
-        // addition to checking the expression support. So we can just use `getEvaluator`.
-        try {
-            getEvaluator(inputSchema, expression, outputType);
-            return true;
-        } catch (UnsupportedOperationException e) {
-            return false;
-        }
-    }
 
     @Override
     public ExpressionEvaluator getEvaluator(

kernel/kernel-defaults/src/test/scala/io/delta/kernel/defaults/engine/DefaultExpressionHandlerSuite.scala

@@ -76,36 +76,6 @@ class DefaultExpressionHandlerSuite extends AnyFunSuite with ExpressionTestUtils
     assert(ex.getMessage.contains("values is null"))
   }
 
-  val tableSchema = new StructType()
-    .add("d1", INTEGER)
-    .add("d2", STRING)
-    .add("d3", new StructType()
-      .add("d31", BOOLEAN)
-      .add("d32", LONG))
-    .add("p1", INTEGER)
-    .add("p2", STRING)
-  val unsupportedExpr = Map(
-    (unsupported("d1"), BOOLEAN) -> false, // unsupported function
-    (lt(col("d1"), int(12)), BOOLEAN) -> true,
-    (lt(col("d1"), int(12)), INTEGER) -> false, // output type is not supported
-    (lt(nestedCol("d3.d32"), int(12)), BOOLEAN) -> true, // implicit conversion from int to long
-    (gt(col("d1"), str("sss")), STRING) -> false, // unexpected input type to > operator
-    // unsupported expression in one of the AND inputs
-    (and(gt(col("d2"), str("sss")), unsupported("d2")), BOOLEAN) -> false,
-    // both unsupported expressions in AND inputs
-    (and(gt(nestedCol("d3.d31"), str("sss")), unsupported("d2")), BOOLEAN) -> false,
-    // unsupported expression in one of the OR inputs
-    (or(gt(col("p2"), str("sss")), unsupported("d2")), BOOLEAN) -> false,
-    // both unsupported expressions in OR inputs
-    (or(gt(nestedCol("d3.d31"), str("sss")), unsupported("d2")), BOOLEAN) -> false
-  ).foreach {
-    case ((expr, outputType), expected) =>
-      test(s"is expression supported: $expr -> $outputType") {
-        assert(
-          new DefaultExpressionHandler().isSupported(tableSchema, expr, outputType) == expected)
-      }
-  }
-
   private def selectionVector(values: Array[Boolean], from: Int, to: Int) = {
     new DefaultExpressionHandler().createSelectionVector(values, from, to)
   }