Use unique index rather than constraint when using formula [like lower(column)]

src/main/java/io/ebeaninternal/dbmigration/ddlgeneration/platform/BaseTableDdl.java

@@ -451,7 +451,7 @@ public class BaseTableDdl implements TableDdl {
     String tableName = lowerTableName(request.table());
     if (request.indexName() != null) {
       // no matching unique constraint so add the index
-      fkeyBuffer.appendStatement(platformDdl.createIndex(request.indexName(), tableName, request.cols()));
+      fkeyBuffer.appendStatement(platformDdl.createIndex(request.indexName(), tableName, request.cols(), false));
     }
 
     alterTableAddForeignKey(write.getOptions(), fkeyBuffer, request);
@@ -609,10 +609,10 @@ public class BaseTableDdl implements TableDdl {
   }
 
   @Override
-  public void generate(DdlWrite writer, CreateIndex createIndex) throws IOException {
-    if (platformInclude(createIndex.getPlatforms())) {
-      writer.apply().appendStatement(platformDdl.createIndex(createIndex.getIndexName(), createIndex.getTableName(), split(createIndex.getColumns())));
-      writer.dropAll().appendStatement(platformDdl.dropIndex(createIndex.getIndexName(), createIndex.getTableName()));
+  public void generate(DdlWrite writer, CreateIndex index) throws IOException {
+    if (platformInclude(index.getPlatforms())) {
+      writer.apply().appendStatement(platformDdl.createIndex(index.getIndexName(), index.getTableName(), split(index.getColumns()), Boolean.TRUE.equals(index.isUnique())));
+      writer.dropAll().appendStatement(platformDdl.dropIndex(index.getIndexName(), index.getTableName()));
     }
   }
 

src/main/java/io/ebeaninternal/dbmigration/ddlgeneration/platform/ClickHouseDdl.java

@@ -61,7 +61,7 @@ public class ClickHouseDdl extends PlatformDdl {
   }
 
   @Override
-  public String createIndex(String indexName, String tableName, String[] columns) {
+  public String createIndex(String indexName, String tableName, String[] columns, boolean unique) {
     return null;
   }
 

src/main/java/io/ebeaninternal/dbmigration/ddlgeneration/platform/HanaColumnStoreDdl.java

@@ -13,7 +13,7 @@ public class HanaColumnStoreDdl extends AbstractHanaDdl {
   }
 
   @Override
-  public String createIndex(String indexName, String tableName, String[] columns) {
+  public String createIndex(String indexName, String tableName, String[] columns, boolean unique) {
     if (columns == null || columns.length == 0) {
       return "-- cannot create index: no columns given";
     }

src/main/java/io/ebeaninternal/dbmigration/ddlgeneration/platform/PlatformDdl.java

@@ -109,6 +109,8 @@ public class PlatformDdl {
 
   protected String addForeignKeySkipCheck = "";
 
+  protected String uniqueIndex = "unique";
+
   /**
    * Set false for MsSqlServer to allow multiple nulls for OneToOne mapping.
    */
@@ -389,12 +391,14 @@ public class PlatformDdl {
   /**
    * Return the create index statement.
    */
-  public String createIndex(String indexName, String tableName, String[] columns) {
-
+  public String createIndex(String indexName, String tableName, String[] columns, boolean unique) {
     StringBuilder buffer = new StringBuilder();
-    buffer.append("create index ").append(maxConstraintName(indexName)).append(" on ").append(tableName);
+    buffer.append("create ");
+    if (unique) {
+      buffer.append(uniqueIndex).append(" ");
+    }
+    buffer.append("index ").append(maxConstraintName(indexName)).append(" on ").append(tableName);
     appendColumns(columns, buffer);
-
     return buffer.toString();
   }
 

src/main/java/io/ebeaninternal/dbmigration/migration/CreateIndex.java

@@ -19,6 +19,7 @@ import javax.xml.bind.annotation.XmlType;
  *       <attribute name="indexName" use="required" type="{http://www.w3.org/2001/XMLSchema}string" />
  *       <attribute name="tableName" use="required" type="{http://www.w3.org/2001/XMLSchema}string" />
  *       <attribute name="columns" use="required" type="{http://www.w3.org/2001/XMLSchema}string" />
+ *       <attribute name="unique" type="{http://www.w3.org/2001/XMLSchema}boolean" />
  *       <attribute name="platforms" type="{http://www.w3.org/2001/XMLSchema}string" />
  *     </restriction>
  *   </complexContent>
@@ -36,6 +37,8 @@ public class CreateIndex {
   protected String tableName;
   @XmlAttribute(name = "columns", required = true)
   protected String columns;
+  @XmlAttribute(name = "unique")
+  protected Boolean unique;
   @XmlAttribute(name = "platforms")
   protected String platforms;
 
@@ -99,6 +102,20 @@ public class CreateIndex {
     this.columns = value;
   }
 
+  /**
+   * Return the unique property.
+   */
+  public Boolean isUnique() {
+    return unique;
+  }
+
+  /**
+   * Set the unique property.
+   */
+  public void setUnique(Boolean unique) {
+    this.unique = unique;
+  }
+
   /**
    * Return the platforms.
    */

src/main/java/io/ebeaninternal/dbmigration/model/MIndex.java

@@ -20,6 +20,8 @@ public class MIndex {
 
   private List<String> columns = new ArrayList<>();
 
+  private boolean unique;
+
   /**
    * Create a single column non unique index.
    */
@@ -29,9 +31,10 @@ public class MIndex {
     this.columns.add(columnName);
   }
 
-  public MIndex(String indexName, String tableName, String[] columnNames, String platforms) {
+  public MIndex(String indexName, String tableName, String[] columnNames, String platforms, boolean unique) {
     this(indexName, tableName, columnNames);
     this.platforms = platforms;
+    this.unique = unique;
   }
 
   /**
@@ -48,6 +51,7 @@ public class MIndex {
     this.tableName = createIndex.getTableName();
     this.columns = split(createIndex.getColumns());
     this.platforms = createIndex.getPlatforms();
+    this.unique = Boolean.TRUE.equals(createIndex.isUnique());
   }
 
   public String getKey() {
@@ -85,6 +89,9 @@ public class MIndex {
     create.setTableName(tableName);
     create.setColumns(join());
     create.setPlatforms(platforms);
+    if (Boolean.TRUE.equals(unique)) {
+      create.setUnique(Boolean.TRUE);
+    }
     return create;
   }
 
@@ -117,6 +124,9 @@ public class MIndex {
     if (!tableName.equals(newIndex.getTableName())) {
       return true;
     }
+    if (unique != newIndex.unique) {
+      return true;
+    }
     List<String> newColumns = newIndex.getColumns();
     if (columns.size() != newColumns.size()) {
       return true;

src/main/java/io/ebeaninternal/dbmigration/model/build/ModelBuildPropertyVisitor.java

@@ -61,7 +61,7 @@ public class ModelBuildPropertyVisitor extends BaseTablePropertyVisitor {
       for (IndexDefinition index : indexes) {
         String[] columns = index.getColumns();
         indexSet.add(columns);
-        if (index.isUnique()) {
+        if (index.isUniqueConstraint()) {
           table.addUniqueConstraint(createMUniqueConstraint(index, columns));
         } else {
           // 'just' an index (not a unique constraint)
@@ -92,7 +92,7 @@ public class ModelBuildPropertyVisitor extends BaseTablePropertyVisitor {
   }
 
   private MIndex createMIndex(String indexName, String tableName, IndexDefinition index) {
-    return new MIndex(indexName, tableName, index.getColumns(), platforms(index.getPlatforms()));
+    return new MIndex(indexName, tableName, index.getColumns(), platforms(index.getPlatforms()), index.isUnique());
   }
 
   private String platforms(Platform[] platforms) {

src/main/java/io/ebeaninternal/server/deploy/IndexDefinition.java

@@ -35,6 +35,22 @@ public class IndexDefinition {
     this.platforms = null;
   }
 
+  /**
+   * Return true if this can be used as a unique constraint.
+   */
+  public boolean isUniqueConstraint() {
+    return unique && noColumnFormulas();
+  }
+
+  private boolean noColumnFormulas() {
+    for (String column : columns) {
+      if (column.contains("(")) {
+        return false;
+      }
+    }
+    return true;
+  }
+
   /**
    * Return true if this is a unique constraint.
    */