Add enum UniqueIndexNullsHandling and fix a typo

h2/src/main/org/h2/engine/Mode.java

@@ -22,6 +22,29 @@ public class Mode {
         REGULAR, DB2, Derby, MSSQLServer, HSQLDB, MySQL, Oracle, PostgreSQL, Ignite,
     }
 
+    /**
+     * Determines how rows with {@code NULL} values in indexed columns are handled
+     * in unique indexes.
+     */
+    public enum UniqueIndexNullsHandling {
+        /**
+         * Multiple identical indexed columns with at least one {@code NULL} value are
+         * allowed in unique index.
+         */
+        ALLOW_DUPLICATES_WITH_ANY_NULL,
+
+        /**
+         * Multiple identical indexed columns with all {@code NULL} values are allowed
+         * in unique index.
+         */
+        ALLOW_DUPLICATES_WITH_ALL_NULLS,
+
+        /**
+         * Multiple identical indexed columns are not allowed in unique index.
+         */
+        FORBID_ANY_DUPLICATES;
+    }
+
     private static final HashMap<String, Mode> MODES = New.hashMap();
 
     // Modes are also documented in the features section
@@ -87,16 +110,10 @@ public class Mode {
     public boolean systemColumns;
 
     /**
-     * <ul>
-     * <li>If {@code 0}, multiple identical indexed columns with at least one
-     * {@code NULL} value are allowed in unique index.</li>
-     * <li>If {@code 1}, multiple identical indexed columns with all {@code NULL}
-     * values are allowed in unique index.</li>
-     * <li>If {@code 2}, multiple identical indexed columns are not allowed in
-     * unique index.</li>
-     * </ul>
+     * Determines how rows with {@code NULL} values in indexed columns are handled
+     * in unique indexes.
      */
-    public byte uniquieIndexNullsHandling;
+    public UniqueIndexNullsHandling uniqueIndexNullsHandling = UniqueIndexNullsHandling.ALLOW_DUPLICATES_WITH_ANY_NULL;
 
     /**
      * Empty strings are treated like NULL values. Useful for Oracle emulation.
@@ -207,7 +224,7 @@ public class Mode {
 
         mode = new Mode(ModeEnum.Derby.name());
         mode.aliasColumnName = true;
-        mode.uniquieIndexNullsHandling = 2;
+        mode.uniqueIndexNullsHandling = UniqueIndexNullsHandling.FORBID_ANY_DUPLICATES;
         mode.supportOffsetFetch = true;
         mode.sysDummy1 = true;
         mode.isolationLevelInSelectOrInsertStatement = true;
@@ -219,7 +236,7 @@ public class Mode {
         mode.aliasColumnName = true;
         mode.convertOnlyToSmallerScale = true;
         mode.nullConcatIsNull = true;
-        mode.uniquieIndexNullsHandling = 2;
+        mode.uniqueIndexNullsHandling = UniqueIndexNullsHandling.FORBID_ANY_DUPLICATES;
         mode.allowPlusForStringConcat = true;
         // HSQLDB does not support client info properties. See
         // http://hsqldb.org/doc/apidocs/
@@ -231,7 +248,7 @@ public class Mode {
         mode = new Mode(ModeEnum.MSSQLServer.name());
         mode.aliasColumnName = true;
         mode.squareBracketQuotedNames = true;
-        mode.uniquieIndexNullsHandling = 2;
+        mode.uniqueIndexNullsHandling = UniqueIndexNullsHandling.FORBID_ANY_DUPLICATES;
         mode.allowPlusForStringConcat = true;
         mode.swapConvertFunctionParameters = true;
         mode.supportPoundSymbolForColumnNames = true;
@@ -259,7 +276,7 @@ public class Mode {
         mode = new Mode(ModeEnum.Oracle.name());
         mode.aliasColumnName = true;
         mode.convertOnlyToSmallerScale = true;
-        mode.uniquieIndexNullsHandling = 1;
+        mode.uniqueIndexNullsHandling = UniqueIndexNullsHandling.ALLOW_DUPLICATES_WITH_ALL_NULLS;
         mode.treatEmptyStringsAsNull = true;
         mode.regexpReplaceBackslashReferences = true;
         mode.supportPoundSymbolForColumnNames = true;

h2/src/main/org/h2/index/BaseIndex.java

@@ -310,35 +310,24 @@ public abstract class BaseIndex extends SchemaObjectBase implements Index {
      *         {@code false otherwise}
      */
     protected boolean mayHaveDuplicates(SearchRow searchRow) {
-        int mode = database.getMode().uniquieIndexNullsHandling;
-        /*
-         * Multiple identical indexed columns with at least one NULL value are allowed
-         * in unique index.
-         */
-        if (mode == 0) {
+        switch (database.getMode().uniqueIndexNullsHandling) {
+        case ALLOW_DUPLICATES_WITH_ANY_NULL:
             for (int index : columnIds) {
                 if (searchRow.getValue(index) == ValueNull.INSTANCE) {
                     return true;
                 }
             }
             return false;
-        }
-        /*
-         * Multiple identical indexed columns with all {@code NULL} values are allowed
-         * in unique index.
-         */
-        if (mode == 1) {
+        case ALLOW_DUPLICATES_WITH_ALL_NULLS:
             for (int index : columnIds) {
                 if (searchRow.getValue(index) != ValueNull.INSTANCE) {
                     return false;
                 }
             }
             return true;
+        default:
+            return false;
         }
-        /*
-         * Multiple identical indexed columns are not allowed in unique index.
-         */
-        return false;
     }
 
     /**