fix: extract magic number into a named constant

Signed-off-by: yuxiqian <34335406+yuxiqian@users.noreply.github.com>

Author: yuxiqian

flink-cdc-connect/flink-cdc-pipeline-connectors/flink-cdc-pipeline-connector-mysql/src/main/java/org/apache/flink/cdc/connectors/mysql/utils/MySqlTypeUtils.java

@@ -107,6 +107,7 @@ public class MySqlTypeUtils {
     private static final String MULTIPOLYGON = "MULTIPOLYGON";
     private static final String MULTILINESTRING = "MULTILINESTRING";
     private static final String UNKNOWN = "UNKNOWN";
+    private static final int FLOAT_LENGTH_UNSPECIFIED_FLAG = -1;
 
     /** Returns a corresponding Flink data type from a debezium {@link Column}. */
     public static DataType fromDbzColumn(Column column) {
@@ -164,7 +165,7 @@ private static DataType convertFromColumn(Column column) {
             case FLOAT:
             case FLOAT_UNSIGNED:
             case FLOAT_UNSIGNED_ZEROFILL:
-                if (column.length() != -1) {
+                if (column.length() != FLOAT_LENGTH_UNSPECIFIED_FLAG) {
                     // For FLOAT types with length provided explicitly, treat it like DOUBLE
                     return DataTypes.DOUBLE();
                 } else {