Remove incorrect useless code from Iceberg TableStatisticsMaker

The code used to extract partition values was useless, because
`Constraint#predicate` is never present there.

The code was also incorrect, because it would assign transformation
value to transformation's source column. For example, it would
instantiate a map like

    a_string_column: 2 (bucket number)

plugin/trino-iceberg/src/main/java/io/trino/plugin/iceberg/TableStatisticsMaker.java

@@ -18,7 +18,6 @@
 import io.trino.spi.connector.ColumnHandle;
 import io.trino.spi.connector.Constraint;
 import io.trino.spi.predicate.Domain;
-import io.trino.spi.predicate.NullableValue;
 import io.trino.spi.predicate.TupleDomain;
 import io.trino.spi.statistics.ColumnStatistics;
 import io.trino.spi.statistics.DoubleRange;
@@ -45,6 +44,7 @@
 import java.util.function.Predicate;
 import java.util.stream.Collectors;
 
+import static com.google.common.base.Verify.verify;
 import static com.google.common.collect.ImmutableList.toImmutableList;
 import static io.trino.plugin.iceberg.ExpressionConverter.toIcebergExpression;
 import static io.trino.plugin.iceberg.IcebergUtil.getColumns;
@@ -198,14 +198,14 @@ private boolean dataFileMatches(
             List<PartitionField> partitionFields,
             Map<Integer, ColumnFieldDetails> fieldDetails)
     {
+        // Currently this method is used only for IcebergMetadata.getTableStatistics and there Constraint never carries a predicate.
+        // TODO support pruning with constraint when this changes.
+        verify(constraint.predicate().isEmpty(), "Unexpected Constraint predicate");
+
         TupleDomain<ColumnHandle> constraintSummary = constraint.getSummary();
 
         Map<ColumnHandle, Domain> domains = constraintSummary.getDomains().get();
 
-        Predicate<Map<ColumnHandle, NullableValue>> predicate = constraint.predicate().orElse(value -> true);
-
-        ImmutableMap.Builder<ColumnHandle, NullableValue> nullableValueBuilder = ImmutableMap.builder();
-
         for (int index = 0; index < partitionFields.size(); index++) {
             PartitionField field = partitionFields.get(index);
             int fieldId = field.sourceId();
@@ -216,21 +216,11 @@ private boolean dataFileMatches(
             if (allowedDomain != null && !allowedDomain.includesNullableValue(value)) {
                 return false;
             }
-            nullableValueBuilder.put(column, makeNullableValue(details.getTrinoType(), value));
-        }
-
-        if (constraint.getPredicateColumns().isPresent()) {
-            return predicate.test(nullableValueBuilder.build());
         }
 
         return true;
     }
 
-    private NullableValue makeNullableValue(io.trino.spi.type.Type type, Object value)
-    {
-        return value == null ? NullableValue.asNull(type) : NullableValue.of(type, value);
-    }
-
     public List<Type> partitionTypes(List<PartitionField> partitionFields, Map<Integer, Type.PrimitiveType> idToTypeMapping)
     {
         ImmutableList.Builder<Type> partitionTypeBuilder = ImmutableList.builder();

plugin/trino-iceberg/src/test/java/io/trino/plugin/iceberg/BaseIcebergConnectorTest.java

@@ -13,6 +13,7 @@
  */
 package io.trino.plugin.iceberg;
 
+import com.google.common.base.VerifyException;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import io.trino.Session;
@@ -28,7 +29,6 @@
 import io.trino.spi.predicate.NullableValue;
 import io.trino.spi.predicate.TupleDomain;
 import io.trino.spi.statistics.ColumnStatistics;
-import io.trino.spi.statistics.DoubleRange;
 import io.trino.spi.statistics.TableStatistics;
 import io.trino.testing.BaseConnectorTest;
 import io.trino.testing.MaterializedResult;
@@ -1517,24 +1517,28 @@ public void testStatisticsConstraints()
         String insertStart = "INSERT INTO iceberg.tpch.test_simple_partitioned_table_statistics";
         assertUpdate(insertStart + " VALUES (1, 101), (2, 102), (3, 103), (4, 104)", 4);
         TableStatistics tableStatistics = getTableStatistics(tableName, new Constraint(TupleDomain.all()));
-
-        // TODO Change to use SHOW STATS FOR table_name when Iceberg applyFilter allows pushdown.
-        // Then I can get rid of the helper methods and direct use of TableStatistics
-
-        Predicate<Map<ColumnHandle, NullableValue>> predicate = new TestRelationalNumberPredicate("col1", 3, i -> i >= 0);
         IcebergColumnHandle col1Handle = getColumnHandleFromStatistics(tableStatistics, "col1");
-        Constraint constraint = new Constraint(TupleDomain.all(), Optional.of(predicate), Optional.of(ImmutableSet.of(col1Handle)));
-        tableStatistics = getTableStatistics(tableName, constraint);
-        assertEquals(tableStatistics.getRowCount().getValue(), 2.0);
-        ColumnStatistics columnStatistics = getStatisticsForColumn(tableStatistics, "col1");
-        assertThat(columnStatistics.getRange()).hasValue(new DoubleRange(3, 4));
-
-        // This shows that Predicate<ColumnHandle, NullableValue> only filters rows for partitioned columns.
-        predicate = new TestRelationalNumberPredicate("col2", 102, i -> i >= 0);
-        tableStatistics = getTableStatistics(tableName, new Constraint(TupleDomain.all(), Optional.of(predicate), Optional.empty()));
-        assertEquals(tableStatistics.getRowCount().getValue(), 4.0);
-        columnStatistics = getStatisticsForColumn(tableStatistics, "col2");
-        assertThat(columnStatistics.getRange()).hasValue(new DoubleRange(101, 104));
+
+        // Constraint.predicate is currently not supported, because it's never provided by the engine.
+        // TODO add (restore) test coverage when this changes.
+
+        // predicate on a partition column
+        assertThatThrownBy(() ->
+                getTableStatistics(tableName, new Constraint(
+                        TupleDomain.all(),
+                        Optional.of(new TestRelationalNumberPredicate("col1", 3, i1 -> i1 >= 0)),
+                        Optional.of(ImmutableSet.of(col1Handle)))))
+                .isInstanceOf(VerifyException.class)
+                .hasMessage("Unexpected Constraint predicate");
+
+        // predicate on an unspecified set of columns column
+        assertThatThrownBy(() ->
+                getTableStatistics(tableName, new Constraint(
+                        TupleDomain.all(),
+                        Optional.of(new TestRelationalNumberPredicate("col2", 102, i -> i >= 0)),
+                        Optional.empty())))
+                .isInstanceOf(VerifyException.class)
+                .hasMessage("Unexpected Constraint predicate");
 
         dropTable(tableName);
     }