Support duplicate index detection, max constraint names - Internal changes for DB Migration / DDL generation #369

src/main/java/com/avaje/ebean/dbmigration/ddlgeneration/platform/BaseTableDdl.java

@@ -23,11 +23,38 @@ public class BaseTableDdl implements TableDdl {
 
   protected final PlatformDdl platformDdl;
 
+  /**
+   * Used to check that indexes on foreign keys should be skipped as a unique index on the columns
+   * already exists.
+   */
+  protected IndexSet indexSet = new IndexSet();
+
+  // counters used when constraint names are truncated due to maximum length
+  // and these counters are used to keep the constraint name unique
+  protected int countCheck;
+  protected int countUnique;
+  protected int countForeignKey;
+  protected int countIndex;
+
+  /**
+   * Construct with a naming convention and platform specific DDL.
+   */
   public BaseTableDdl(DdlNamingConvention namingConvention, PlatformDdl platformDdl) {
     this.namingConvention = namingConvention;
     this.platformDdl = platformDdl;
   }
 
+  /**
+   * Reset counters and index set for each table.
+   */
+  protected void reset() {
+    indexSet.clear();
+    countCheck = 0;
+    countUnique = 0;
+    countForeignKey = 0;
+    countIndex = 0;
+  }
+
   /**
    * Generate the appropriate 'create table' and matching 'drop table' statements
    * and add them to the 'apply' and 'rollback' buffers.
@@ -35,6 +62,8 @@ public class BaseTableDdl implements TableDdl {
   @Override
   public void generate(DdlWrite writer, CreateTable createTable) throws IOException {
 
+    reset();
+
     String tableName = lowerName(createTable.getName());
     List<Column> columns = createTable.getColumn();
     List<Column> pk = determinePrimaryKeyColumns(columns);
@@ -176,15 +205,21 @@ public class BaseTableDdl implements TableDdl {
 
     String indexName = determineForeignKeyIndexName(tableName, columns);
 
-    fkeyBuffer.append("create index ").append(indexName).append(" on ").append(tableName);
-    appendColumns(columns, fkeyBuffer);
-    fkeyBuffer.endOfStatement();
+    boolean addIndex = indexSet.add(columns);
+    if (addIndex) {
+      // no matching unique constraint so add the index
+      fkeyBuffer.append("create index ").append(indexName).append(" on ").append(tableName);
+      appendColumns(columns, fkeyBuffer);
+      fkeyBuffer.endOfStatement();
+    }
 
     fkeyBuffer.end();
 
-    write.rollbackForeignKeys()
-        .append("drop index ").append(indexName)
-        .endOfStatement();
+    if (addIndex) {
+      write.rollbackForeignKeys()
+          .append("drop index ").append(indexName)
+          .endOfStatement();
+    }
 
     write.rollbackForeignKeys()
         .append("alter table ").append(tableName).append(" drop constraint ").append(fkName)
@@ -253,6 +288,7 @@ public class BaseTableDdl implements TableDdl {
     for (Column column : columns) {
       if (isTrue(column.isUnique())) {
         inlineUniqueConstraintSingle(apply, createTable.getName(), column);
+        indexSet.add(column);
       }
     }
   }
@@ -369,7 +405,7 @@ public class BaseTableDdl implements TableDdl {
    */
   protected String determineForeignKeyConstraintName(String tableName, String columnName) {
 
-    return namingConvention.foreignKeyConstraintName(tableName, columnName);
+    return namingConvention.foreignKeyConstraintName(tableName, columnName, ++countForeignKey);
   }
 
   /**
@@ -377,7 +413,7 @@ public class BaseTableDdl implements TableDdl {
    */
   protected String determineForeignKeyIndexName(String tableName, String[] columns) {
 
-    return namingConvention.foreignKeyIndexName(tableName, columns);
+    return namingConvention.foreignKeyIndexName(tableName, columns, ++countIndex);
   }
 
   /**
@@ -385,7 +421,7 @@ public class BaseTableDdl implements TableDdl {
    */
   protected String determineUniqueConstraintName(String tableName, String columnName) {
 
-    return namingConvention.uniqueConstraintName(tableName, columnName);
+    return namingConvention.uniqueConstraintName(tableName, columnName, ++countUnique);
   }
 
   /**
@@ -393,7 +429,7 @@ public class BaseTableDdl implements TableDdl {
    */
   protected String determineCheckConstraintName(String tableName, String columnName) {
 
-    return namingConvention.checkConstraintName(tableName, columnName);
+    return namingConvention.checkConstraintName(tableName, columnName, ++countCheck);
   }
 
   /**
@@ -427,4 +463,82 @@ public class BaseTableDdl implements TableDdl {
     return (value == null) ? 0 : value.intValue();
   }
 
+
+  /**
+   * The indexes held on the table.
+   * <p>
+   * Used to detect when we don't need to add an index on the foreign key columns
+   * when there is an existing unique constraint with the same columns.
+   */
+  protected static class IndexSet {
+
+    private List<IndexColumns> indexes = new ArrayList<IndexColumns>();
+
+    /**
+     * Clear the indexes (for each table).
+     */
+    public void clear() {
+      indexes.clear();
+    }
+
+    /**
+     * Add an index for the given column.
+     */
+    public void add(Column column) {
+      indexes.add(new IndexColumns(column));
+    }
+
+    /**
+     * Return true if an index should be added for the given columns.
+     * <p>
+     * Returning false indicates there is an existing index (unique constraint) with these columns
+     * and that an extra index should not be added.
+     * </p>
+     */
+    public boolean add(String[] columns) {
+      IndexColumns newIndex = new IndexColumns(columns);
+      for (int i = 0; i <indexes.size() ; i++) {
+        if (indexes.get(i).isMatch(newIndex)) {
+          return false;
+        }
+      }
+      indexes.add(newIndex);
+      return true;
+    }
+  }
+
+  /**
+   * Set of columns making up a particular index (column order is important).
+   */
+  protected static class IndexColumns {
+
+    List<String> columns = new ArrayList<String>(4);
+
+    /**
+     * Construct representing as a single column index.
+     */
+    public IndexColumns(Column column) {
+      columns.add(column.getName());
+    }
+
+    /**
+     * Construct representing index.
+     */
+    public IndexColumns(String[] columnNames) {
+      for (int i = 0; i <columnNames.length; i++) {
+        columns.add(columnNames[i]);
+      }
+    }
+
+    /**
+     * Return true if there this index match (same columns same order).
+     */
+    public boolean isMatch(IndexColumns other) {
+      return columns.equals(other.columns);
+    }
+
+    protected void add(String column) {
+      columns.add(column);
+    }
+  }
 }

src/main/java/com/avaje/ebean/dbmigration/ddlgeneration/platform/DdlNamingConvention.java

@@ -22,6 +22,8 @@ public class DdlNamingConvention {
   protected String ckPrefix = "ck_";
   protected String ckSuffix = "";
 
+  protected int maxConstraintNameLength = 32;
+
   protected boolean lowerCaseNames = true;
 
   protected DdlNameNormalise normalise = new DdlNameNormalise();
@@ -34,20 +36,20 @@ public class DdlNamingConvention {
    */
   public String primaryKeyName(String tableName) {
 
-    return pkPrefix + normaliseTable(tableName) + pkSuffix;
+    return maxLength(pkPrefix + normaliseTable(tableName) + pkSuffix, 0);
   }
 
   /**
    * Return the foreign key constraint name given a single column foreign key.
    */
-  public String foreignKeyConstraintName(String tableName, String columnName) {
-    return fkPrefix + normaliseTable(tableName) + fkMiddle + normaliseColumn(columnName) + fkSuffix;
+  public String foreignKeyConstraintName(String tableName, String columnName, int foreignKeyCount) {
+    return maxLength(fkPrefix + normaliseTable(tableName) + fkMiddle + normaliseColumn(columnName) + fkSuffix, foreignKeyCount);
   }
 
   /**
    * Return the index name associated with a foreign key constraint given a single column foreign key.
    */
-  public String foreignKeyIndexName(String tableName, String[] columns) {
+  public String foreignKeyIndexName(String tableName, String[] columns, int indexCount) {
 
     String colPart;
     if (columns.length == 1) {
@@ -62,24 +64,23 @@ public class DdlNamingConvention {
       }
       colPart = sb.toString();
     }
-    //FIXME: apply max length
-    return fkIndexPrefix + normaliseTable(tableName) + fkIndexMiddle + colPart + fkIndexSuffix;
+    return maxLength(fkIndexPrefix + normaliseTable(tableName) + fkIndexMiddle + colPart + fkIndexSuffix, indexCount);
   }
 
   /**
    * Return the unique constraint name.
    */
-  public String uniqueConstraintName(String tableName, String columnName) {
+  public String uniqueConstraintName(String tableName, String columnName, int indexCount) {
 
-    return uqPrefix + normaliseTable(tableName) + "_" + normaliseColumn(columnName) + uqSuffix;
+    return maxLength(uqPrefix + normaliseTable(tableName) + "_" + normaliseColumn(columnName) + uqSuffix, indexCount);
   }
 
   /**
    * Return the check constraint name.
    */
-  public String checkConstraintName(String tableName, String columnName) {
+  public String checkConstraintName(String tableName, String columnName, int checkCount) {
 
-    return ckPrefix + normaliseTable(tableName) + "_" + normaliseColumn(columnName) + ckSuffix;
+    return maxLength(ckPrefix + normaliseTable(tableName) + "_" + normaliseColumn(columnName) + ckSuffix, checkCount);
   }
 
   /**
@@ -95,6 +96,18 @@ public class DdlNamingConvention {
     return (sequenceName != null) ? lowerName(sequenceName) : normaliseTable(tableName) + "_seq";
   }
 
+  /**
+   * Apply a maximum length to the constraint name.
+   */
+  protected String maxLength(String constraintName, int count) {
+    if (constraintName.length() < maxConstraintNameLength) {
+      return constraintName;
+    }
+    // add the count to ensure the constraint name is unique
+    // (relying on the prefix having the table name to be globally unique)
+    return constraintName.substring(0,maxConstraintNameLength-3)+"_"+count;
+  }
+
   /**
    * Normalise the table name by trimming catalog and schema and removing any
    * quoted identifier characters (",',[,] etc).

src/main/java/com/avaje/ebean/dbmigration/ddlgeneration/platform/PlatformDdl.java

@@ -30,6 +30,8 @@ public class PlatformDdl {
    */
   protected String dropTableIfExists = "drop table if exists ";
 
+  protected String dropTableCascade = "";
+
   /**
    * Default assumes if exists is supported.
    */
@@ -107,7 +109,7 @@ public class PlatformDdl {
   }
 
   public String dropTable(String tableName) {
-    return dropTableIfExists + tableName;
+    return dropTableIfExists + tableName + dropTableCascade;
   }
 
   public String lowerName(String name) {