FIX: optimized unique constraint handling for platforms that does support them on nullable columns (#1095)

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

@@ -207,9 +207,12 @@ public class BaseTableDdl implements TableDdl {
     String tableName = createTable.getName();
     for (Column col : externalUnique) {
       String uqName = col.getUniqueOneToOne();
+      if (uqName == null) {
+        uqName = col.getUnique();
+      }
       String[] columnNames = {col.getName()};
       write.apply()
-        .append(platformDdl.alterTableAddUniqueConstraint(tableName, uqName, columnNames))
+        .append(platformDdl.alterTableAddUniqueConstraint(tableName, uqName, columnNames, Boolean.TRUE.equals(col.isNotnull())))
         .endOfStatement();
 
       write.dropAllForeignKeys()
@@ -221,7 +224,7 @@ public class BaseTableDdl implements TableDdl {
       String uqName = constraint.getName();
       String[] columnNames = StringHelper.delimitedToArray(constraint.getColumnNames(), ",", false);
       write.apply()
-        .append(platformDdl.alterTableAddUniqueConstraint(tableName, uqName, columnNames))
+        .append(platformDdl.alterTableAddUniqueConstraint(tableName, uqName, columnNames, false)) // TODO: check if nullable
         .endOfStatement();
 
       write.dropAllForeignKeys()
@@ -421,9 +424,9 @@ public class BaseTableDdl implements TableDdl {
   protected void writeCompoundUniqueConstraints(DdlBuffer apply, CreateTable createTable) throws IOException {
 
     List<UniqueConstraint> uniqueConstraints = createTable.getUniqueConstraint();
-    boolean inlineUniqueCompound = platformDdl.isInlineUniqueOneToOne();
+    boolean inlineUniqueWhenNull = platformDdl.isInlineUniqueWhenNullable();
     for (UniqueConstraint uniqueConstraint : uniqueConstraints) {
-       if (inlineUniqueCompound) {
+       if (inlineUniqueWhenNull) {
         String uqName = uniqueConstraint.getName();
         String[] columns = toColumnNamesSplit(uniqueConstraint.getColumnNames());
         apply.append(",").newLine();
@@ -440,17 +443,18 @@ public class BaseTableDdl implements TableDdl {
    */
   protected void writeUniqueConstraints(DdlBuffer apply, CreateTable createTable) throws IOException {
 
-    boolean inlineUniqueOneToOne = platformDdl.isInlineUniqueOneToOne();
+    boolean inlineUniqueWhenNullable = platformDdl.isInlineUniqueWhenNullable();
 
     List<Column> columns = createTable.getColumn();
     for (Column column : columns) {
-      if (hasValue(column.getUnique()) || (inlineUniqueOneToOne && hasValue(column.getUniqueOneToOne()))) {
-        // normal mechanism for adding unique constraint
-        inlineUniqueConstraintSingle(apply, column);
-
-      } else if (!inlineUniqueOneToOne && hasValue(column.getUniqueOneToOne())) {
-        // MsSqlServer specific mechanism for adding unique constraints (that allow nulls)
-        externalUnique.add(column);
+      if (hasValue(column.getUnique()) || hasValue(column.getUniqueOneToOne())) {
+        if (Boolean.TRUE.equals(column.isNotnull()) || inlineUniqueWhenNullable) {
+          // normal mechanism for adding unique constraint
+          inlineUniqueConstraintSingle(apply, column);
+        } else {
+          // MsSqlServer & DB2 specific mechanism for adding unique constraints (that allow nulls)
+          externalUnique.add(column);
+        }
       }
     }
   }
@@ -834,9 +838,9 @@ public class BaseTableDdl implements TableDdl {
   protected void addUniqueConstraint(DdlWrite writer, AlterColumn alter, String uqName) throws IOException {
 
     String[] cols = {alter.getColumnName()};
-
+    boolean notNull = alter.isNotnull() != null ? alter.isNotnull() : Boolean.TRUE.equals(alter.isNotnull());
     writer.apply()
-      .append(platformDdl.alterTableAddUniqueConstraint(alter.getTableName(), uqName, cols))
+      .append(platformDdl.alterTableAddUniqueConstraint(alter.getTableName(), uqName, cols, notNull))
       .endOfStatement();
 
     writer.dropAllForeignKeys()

src/main/java/io/ebean/dbmigration/ddlgeneration/platform/DB2Ddl.java

@@ -10,6 +10,16 @@ public class DB2Ddl extends PlatformDdl {
   public DB2Ddl(DatabasePlatform platform) {
     super(platform);
     this.identitySuffix = " generated by default as identity";
+    this.inlineUniqueWhenNullable = false;
+  }
+  
+  public String alterTableAddUniqueConstraint(String tableName, String uqName, String[] columns, boolean notNull) {
+    if (notNull) {
+      return super.alterTableAddUniqueConstraint(tableName, uqName, columns, true);
+    } else {
+      // Hmm: Complex workaround: https://www.ibm.com/developerworks/mydeveloperworks/blogs/SQLTips4DB2LUW/entry/unique_where_not_null_indexes26?lang=en
+      return "-- NOT SUPPORTED " + super.alterTableAddUniqueConstraint(tableName, uqName, columns, true);
+    }
   }
 
 }

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

@@ -91,7 +91,7 @@ public class PlatformDdl {
   /**
    * Set false for MsSqlServer to allow multiple nulls for OneToOne mapping.
    */
-  protected boolean inlineUniqueOneToOne = true;
+  protected boolean inlineUniqueWhenNullable = true;
 
   protected DbConstraintNaming naming;
 
@@ -371,7 +371,7 @@ public class PlatformDdl {
    * <p>
    * Overridden by MsSqlServer for specific null handling on unique constraints.
    */
-  public String alterTableAddUniqueConstraint(String tableName, String uqName, String[] columns) {
+  public String alterTableAddUniqueConstraint(String tableName, String uqName, String[] columns, boolean notNull) {
 
     StringBuilder buffer = new StringBuilder(90);
     buffer.append("alter table ").append(tableName).append(" add constraint ").append(uqName).append(" unique ");
@@ -401,11 +401,12 @@ public class PlatformDdl {
   }
 
   /**
-   * Return true if unique constraints for OneToOne can be inlined as normal.
-   * Returns false for MsSqlServer due to it's null handling for unique constraints.
+   * Return true if unique constraints for nullable columns can be inlined as normal.
+   * Returns false for MsSqlServer & DB2 due to it's not possible to to put a constraint
+   * on a nullable column
    */
-  public boolean isInlineUniqueOneToOne() {
-    return inlineUniqueOneToOne;
+  public boolean isInlineUniqueWhenNullable() {
+    return inlineUniqueWhenNullable;
   }
 
   /**

src/main/java/io/ebean/dbmigration/ddlgeneration/platform/SqlServerDdl.java

@@ -17,7 +17,7 @@ public class SqlServerDdl extends PlatformDdl {
     this.foreignKeyRestrict = "";
     this.alterTableIfExists = "";
     this.addColumn = "add";
-    this.inlineUniqueOneToOne = false;
+    this.inlineUniqueWhenNullable = false;
     this.columnSetDefault = "add default";
     this.dropConstraintIfExists = "drop constraint";
     this.historyDdl = new SqlServerHistoryDdl();
@@ -51,8 +51,13 @@ public class SqlServerDdl extends PlatformDdl {
    * MsSqlServer specific null handling on unique constraints.
    */
   @Override
-  public String alterTableAddUniqueConstraint(String tableName, String uqName, String[] columns) {
-
+  public String alterTableAddUniqueConstraint(String tableName, String uqName, String[] columns, boolean notNull) {
+    if (notNull) {
+      return super.alterTableAddUniqueConstraint(tableName, uqName, columns, notNull);
+    }
+    if (uqName == null) {
+      throw new NullPointerException();
+    }
     // issues#233
     String start = "create unique nonclustered index " + uqName + " on " + tableName + "(";
     StringBuilder sb = new StringBuilder(start);