PLUGIN-1925: Introduce Custom BigDecimal Splitter

Author: sgarg-CS

database-commons/src/main/java/io/cdap/plugin/db/source/CustomBigDecimalSplitter.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright © 2025 Cask Data, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package io.cdap.plugin.db.source;
+
+import org.apache.hadoop.mapreduce.lib.db.BigDecimalSplitter;
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+
+/**
+ * Custom implementation of {@link BigDecimalSplitter} to ensures safe and precise division of BigDecimal values while
+ * calculating split points for NUMERIC and DECIMAL types.
+ */
+public class CustomBigDecimalSplitter extends BigDecimalSplitter {
+
+  public static final int SCALE_BUFFER = 5;
+  /**
+   * Performs safe division with correct scale handling.
+   *
+   * @param numerator   the dividend (BigDecimal)
+   * @param denominator the divisor (BigDecimal)
+   * @return quotient with derived scale
+   * @throws ArithmeticException if denominator is zero
+   */
+  @Override
+  protected BigDecimal tryDivide(BigDecimal numerator, BigDecimal denominator) {
+    if (denominator.compareTo(numerator) == 0) {
+      throw new ArithmeticException("Numerator and Denominator are equal in splitter");
+    }
+    if (denominator.compareTo(BigDecimal.ZERO) == 0) {
+      throw new ArithmeticException("Division by zero in splitter");
+    }
+    // Derive scale from numerator/denominator + buffer
+    int effectiveScale = Math.max(numerator.scale(), denominator.scale()) + SCALE_BUFFER;
+    return numerator.divide(denominator, effectiveScale, RoundingMode.HALF_UP);
+  }
+}

database-commons/src/main/java/io/cdap/plugin/db/source/DataDrivenETLDBInputFormat.java

@@ -28,6 +28,7 @@
 import org.apache.hadoop.mapreduce.TaskAttemptContext;
 import org.apache.hadoop.mapreduce.lib.db.DBConfiguration;
 import org.apache.hadoop.mapreduce.lib.db.DBInputFormat;
+import org.apache.hadoop.mapreduce.lib.db.DBSplitter;
 import org.apache.hadoop.mapreduce.lib.db.DBWritable;
 import org.apache.hadoop.mapreduce.lib.db.DataDrivenDBInputFormat;
 import org.slf4j.Logger;
@@ -39,6 +40,7 @@
 import java.sql.DriverManager;
 import java.sql.SQLException;
 import java.sql.Statement;
+import java.sql.Types;
 import java.util.Properties;
 
 /**
@@ -128,6 +130,14 @@ public Connection createConnection() {
     return getConnection();
   }
 
+  @Override
+  protected DBSplitter getSplitter(int sqlDataType) {
+    if (sqlDataType == Types.NUMERIC || sqlDataType == Types.DECIMAL) {
+      return new CustomBigDecimalSplitter();
+    }
+    return super.getSplitter(sqlDataType);
+  }
+
   @Override
   public RecordReader createDBRecordReader(DBInputSplit split, Configuration conf) throws IOException {
     final RecordReader dbRecordReader = super.createDBRecordReader(split, conf);

database-commons/src/test/java/io/cdap/plugin/db/source/CustomBigDecimalSplitterTest.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright © 2025 Cask Data, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package io.cdap.plugin.db.source;
+
+import org.junit.Test;
+import java.math.BigDecimal;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Test class for {@link CustomBigDecimalSplitter}
+ */
+public class CustomBigDecimalSplitterTest {
+  private final CustomBigDecimalSplitter splitter = new CustomBigDecimalSplitter();
+
+  @Test
+  public void testSmallRangeDivision() {
+    BigDecimal result = splitter.tryDivide(BigDecimal.ONE, new BigDecimal("4"));
+    assertEquals(new BigDecimal("0.25000"), result);
+  }
+
+  @Test
+  public void testLargePrecision() {
+    BigDecimal numerator = new BigDecimal("1.0000000000000000001");
+    BigDecimal denominator = new BigDecimal("3");
+    BigDecimal result = splitter.tryDivide(numerator, denominator);
+    assertTrue(result.compareTo(BigDecimal.ZERO) > 0);
+  }
+
+  @Test
+  public void testDivisionByZero() {
+    assertThrows(ArithmeticException.class, () ->
+      splitter.tryDivide(BigDecimal.ONE, BigDecimal.ZERO));
+  }
+
+  @Test
+  public void testZeroNumerator() {
+    // when minVal == maxVal
+    BigDecimal result = splitter.tryDivide(BigDecimal.ZERO, BigDecimal.ONE);
+    assertEquals(0, result.compareTo(BigDecimal.ZERO));
+  }
+}