[PECO-2135] getColumns discrepancy with Databricks Driver (#609)

* column size and nullable col fixed

Author: shivam2680

src/main/java/com/databricks/jdbc/dbclient/impl/common/MetadataResultSetBuilder.java

@@ -125,12 +125,6 @@ static List<List<Object>> getRows(ResultSet resultSet, List<ResultColumn> column
                 } else {
                   object = "NO";
                 }
-              } else if (column.getColumnName().equals(NULLABLE_COLUMN.getColumnName())) {
-                if (object == null || object.equals("true")) {
-                  object = 1;
-                } else {
-                  object = 0;
-                }
               } else if (column.getColumnName().equals(DECIMAL_DIGITS_COLUMN.getColumnName())
                   || column.getColumnName().equals(NUM_PREC_RADIX_COLUMN.getColumnName())) {
                 if (object == null) {
@@ -156,25 +150,33 @@ static List<List<Object>> getRows(ResultSet resultSet, List<ResultColumn> column
                 object = null;
               }
             }
-
+            if (column.getColumnName().equals(NULLABLE_COLUMN.getColumnName())) {
+              object = resultSet.getObject(IS_NULLABLE_COLUMN.getResultSetColumnName());
+              if (object == null || object.equals("true")) {
+                object = 1;
+              } else {
+                object = 0;
+              }
+            }
             if (column.getColumnName().equals(TABLE_TYPE_COLUMN.getColumnName())
                 && (object == null || object.equals(""))) {
               object = "TABLE";
             }
 
             // Handle TYPE_NAME separately for potential modifications
-            if (column.getColumnName().equals(TYPE_NAME_COLUMN.getColumnName())) {
+            if (column.getColumnName().equals(COLUMN_TYPE_COLUMN.getColumnName())) {
               object = stripTypeName((String) object);
             }
             // Set COLUMN_SIZE to 255 if it's not present
             if (column.getColumnName().equals(COLUMN_SIZE_COLUMN.getColumnName())
                 && object == null) {
               // check if typeVal is a text related field
               String typeVal = resultSet.getString(COLUMN_TYPE_COLUMN.getResultSetColumnName());
-              if (typeVal != null && isTextType(typeVal)) {
-                object = 255;
-              } else {
+              if (typeVal == null) {
                 object = 0;
+              } else {
+                int columnSize = getSizeFromTypeVal(typeVal);
+                object = (columnSize != -1) ? columnSize : (isTextType(typeVal) ? 255 : 0);
               }
             }
 
@@ -189,6 +191,34 @@ static List<List<Object>> getRows(ResultSet resultSet, List<ResultColumn> column
     return rows;
   }
 
+  /**
+   * Extracts the size from a SQL type definition in the format DATA_TYPE(size).
+   *
+   * @param typeVal The SQL type string (e.g., "VARCHAR(5000)", "CHAR(100)").
+   * @return The size as an integer, or -1 if the size cannot be determined.
+   */
+  static int getSizeFromTypeVal(String typeVal) {
+    if (typeVal.isEmpty()) {
+      return -1; // Return -1 for invalid input
+    }
+
+    // Regular expression to match DATA_TYPE(size) and extract the size
+    String regex = "\\w+\\((\\d+)\\)";
+    java.util.regex.Pattern pattern =
+        java.util.regex.Pattern.compile(regex, java.util.regex.Pattern.CASE_INSENSITIVE);
+    java.util.regex.Matcher matcher = pattern.matcher(typeVal);
+
+    if (matcher.find()) {
+      try {
+        return Integer.parseInt(matcher.group(1));
+      } catch (NumberFormatException e) {
+        return -1;
+      }
+    }
+
+    return -1;
+  }
+
   static int getBufferLength(String typeVal, int columnSize) {
     if (typeVal == null || typeVal.isEmpty()) {
       return 0;

src/test/java/com/databricks/jdbc/dbclient/impl/common/MetadataResultSetBuilderTest.java

@@ -110,6 +110,14 @@ private static Stream<Arguments> getBufferLengthArguments() {
         Arguments.of("TEXT", 10, 255));
   }
 
+  private static Stream<Arguments> getSizeFromTypeValArguments() {
+    return Stream.of(
+        Arguments.of("VARCHAR(100)", 100),
+        Arguments.of("VARCHAR", -1),
+        Arguments.of("char(10)", 10),
+        Arguments.of("", -1));
+  }
+
   private static Stream<Arguments> getRowsTableTypeColumnArguments() {
     return Stream.of(
         Arguments.of("TABLE", "TABLE"),
@@ -143,7 +151,7 @@ void testGetRowsHandlesNullableColumn(String isNullableValue, int expectedNullab
       throws SQLException {
     ResultSet resultSet = mock(ResultSet.class);
     Mockito.when(resultSet.next()).thenReturn(true).thenReturn(false);
-    Mockito.when(resultSet.getObject(NULLABLE_COLUMN.getResultSetColumnName()))
+    Mockito.when(resultSet.getObject(IS_NULLABLE_COLUMN.getResultSetColumnName()))
         .thenReturn(isNullableValue);
 
     List<List<Object>> rows = MetadataResultSetBuilder.getRows(resultSet, COLUMN_COLUMNS);
@@ -160,6 +168,13 @@ public void testGetBufferLength(String typeVal, int columnSize, int expected) {
     assertEquals(expected, actual);
   }
 
+  @ParameterizedTest
+  @MethodSource("getSizeFromTypeValArguments")
+  public void testGetSizeFromTypeVal(String typeVal, int expected) {
+    int actual = MetadataResultSetBuilder.getSizeFromTypeVal(typeVal);
+    assertEquals(expected, actual);
+  }
+
   @ParameterizedTest
   @MethodSource("stripTypeNameArguments")
   public void testStripTypeName(String input, String expected) {