#414 - Enh info: @History support for H2

src/main/java/com/avaje/ebean/config/dbplatform/DbViewHistorySupport.java

@@ -55,7 +55,7 @@ public abstract class DbViewHistorySupport implements DbHistorySupport {
   public String getAsOfPredicate(String asOfTableAlias, String asOfSysPeriod) {
 
     // (sys_period_start < ? and (sys_period_end is null or sys_period_end > ?));
-    return "(" + asOfTableAlias + "." + asOfSysPeriod + "_start" + " < ? and (" + asOfTableAlias + "." + asOfSysPeriod + "_end" + " is null or " + asOfTableAlias + "." + asOfSysPeriod + "_end" + " > ?))";
+    return "(" + asOfTableAlias + "." + asOfSysPeriod + "_start" + " <= ? and (" + asOfTableAlias + "." + asOfSysPeriod + "_end" + " is null or " + asOfTableAlias + "." + asOfSysPeriod + "_end" + " > ?))";
   }
 
   /**

src/main/java/com/avaje/ebean/config/dbplatform/H2HistorySupport.java

@@ -0,0 +1,8 @@
+package com.avaje.ebean.config.dbplatform;
+
+/**
+ * Runtime support for @History with H2.
+ */
+public class H2HistorySupport extends DbViewHistorySupport {
+
+}

src/main/java/com/avaje/ebean/config/dbplatform/H2HistoryTrigger.java

@@ -0,0 +1,127 @@
+package com.avaje.ebean.config.dbplatform;
+
+import org.h2.api.Trigger;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Timestamp;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * H2 database trigger used to populate history tables to support the @History feature.
+ */
+public class H2HistoryTrigger implements Trigger {
+
+  private static final Logger logger = LoggerFactory.getLogger(H2HistoryTrigger.class);
+
+  /**
+   * Hardcoding the column and history table suffix for now. Not sure how to get that
+   * configuration into the trigger instance nicely as it is instantiated by H2.
+   */
+  private static final String SYS_PERIOD_START = "SYS_PERIOD_START";
+  private static final String SYS_PERIOD_END = "SYS_PERIOD_END";
+  private static final String HISTORY_SUFFIX = "_history";
+
+  /**
+   * SQL to insert into the history table.
+   */
+  private String insertHistorySql;
+
+  /**
+   * Position of SYS_PERIOD_START column in the Object[].
+   */
+  private int effectStartPosition;
+
+  /**
+   * Position of SYS_PERIOD_END column in the Object[].
+   */
+  private int effectEndPosition;
+
+  @Override
+  public void init(Connection conn, String schemaName, String triggerName, String tableName, boolean before, int type) throws SQLException {
+
+    // get the columns for the table
+    ResultSet rs = conn.getMetaData().getColumns(null, schemaName, tableName, null);
+
+    // build the insert into history table SQL
+    StringBuilder insertSql = new StringBuilder(150);
+    insertSql.append("insert into ").append(tableName).append(HISTORY_SUFFIX).append(" (");
+
+    int count = 0;
+    List<String> columns = new ArrayList<String>();
+    while (rs.next()) {
+      if (++count > 1) {
+        insertSql.append(",");
+      }
+      String columnName = rs.getString("COLUMN_NAME");
+      if (columnName.equalsIgnoreCase(SYS_PERIOD_START)) {
+        this.effectStartPosition = count - 1;
+      } else if (columnName.equalsIgnoreCase(SYS_PERIOD_END)) {
+        this.effectEndPosition = count - 1;
+      }
+      insertSql.append(columnName);
+      columns.add(columnName);
+    }
+    insertSql.append(") values (");
+    for (int i = 0; i < count; i++) {
+      if (i > 0) {
+        insertSql.append(",");
+      }
+      insertSql.append("?");
+    }
+    insertSql.append(");");
+
+    this.insertHistorySql = insertSql.toString();
+    logger.debug("History table insert sql: {}", insertHistorySql);
+  }
+
+  @Override
+  public void fire(Connection connection, Object[] oldRow, Object[] newRow) throws SQLException {
+
+    if (oldRow != null) {
+      // a delete or update event
+      Timestamp now = new Timestamp(System.currentTimeMillis());
+      oldRow[effectEndPosition] = now;
+      if (newRow != null) {
+        // update event. Set the effective start timestamp to now.
+        newRow[effectStartPosition] = now;
+      }
+      if (logger.isDebugEnabled()) {
+        logger.debug("History insert: {}", Arrays.toString(oldRow));
+      }
+      insertIntoHistory(connection, oldRow);
+    }
+  }
+
+  /**
+   * Insert the data into the history table.
+   */
+  private void insertIntoHistory(Connection connection, Object[] oldRow) throws SQLException {
+
+    PreparedStatement stmt = connection.prepareStatement(insertHistorySql);
+    try {
+      for (int i = 0; i < oldRow.length; i++) {
+        stmt.setObject(i + 1, oldRow[i]);
+      }
+      stmt.executeUpdate();
+    } finally {
+      stmt.close();
+    }
+  }
+
+  @Override
+  public void close() throws SQLException {
+
+  }
+
+  @Override
+  public void remove() throws SQLException {
+
+  }
+}

src/main/java/com/avaje/ebean/config/dbplatform/H2Platform.java

@@ -15,6 +15,7 @@ public class H2Platform extends DatabasePlatform {
     this.name = "h2";
     this.dbEncrypt = new H2DbEncrypt();
     this.platformDdl = new H2Ddl(this.dbTypeMap, dbIdentity);
+    this.historySupport = new H2HistorySupport();
 
     // only support getGeneratedKeys with non-batch JDBC
     // so generally use SEQUENCE instead of IDENTITY for H2

src/main/java/com/avaje/ebean/dbmigration/ddlgeneration/platform/H2Ddl.java

@@ -10,6 +10,7 @@ public class H2Ddl extends PlatformDdl {
 
   public H2Ddl(DbTypeMap platformTypes, DbIdentity dbIdentity) {
     super(platformTypes, dbIdentity);
+    this.historyDdl = new H2HistoryDdl();
   }
 
 }

src/main/java/com/avaje/ebean/dbmigration/ddlgeneration/platform/H2HistoryDdl.java

@@ -0,0 +1,73 @@
+package com.avaje.ebean.dbmigration.ddlgeneration.platform;
+
+import com.avaje.ebean.config.dbplatform.H2HistoryTrigger;
+import com.avaje.ebean.dbmigration.ddlgeneration.DdlBuffer;
+import com.avaje.ebean.dbmigration.ddlgeneration.DdlWrite;
+import com.avaje.ebean.dbmigration.model.MTable;
+
+import java.io.IOException;
+import java.util.List;
+
+/**
+ * H2 history support using DB triggers to maintain a history table.
+ */
+public class H2HistoryDdl extends DbTriggerBasedHistoryDdl {
+
+  private static final String TRIGGER_CLASS = H2HistoryTrigger.class.getName();
+
+  public H2HistoryDdl() {
+  }
+
+  @Override
+  protected void dropTriggers(DdlBuffer buffer, String baseTable) throws IOException {
+
+    buffer.append("drop trigger ").append(updateTriggerName(baseTable)).endOfStatement();
+  }
+
+  @Override
+  protected void createTriggers(DdlWrite writer, MTable table) throws IOException {
+
+    String baseTableName = table.getName();
+    String historyTableName = historyTableName(baseTableName);
+    List<String> includedColumns = includedColumnNames(table);
+
+    DdlBuffer apply = writer.applyHistory();
+
+    addCreateTrigger(apply, updateTriggerName(baseTableName), baseTableName, historyTableName, includedColumns);
+  }
+
+  @Override
+  protected void regenerateHistoryTriggers(DdlWrite writer, MTable table, HistoryTableUpdate update) throws IOException {
+
+    String baseTableName = table.getName();
+    String historyTableName = historyTableName(baseTableName);
+    List<String> includedColumns = includedColumnNames(table);
+
+    DdlBuffer apply = writer.applyHistory();
+
+    apply.append("-- Regenerated ").newLine();
+    apply.append("-- changes: ").append(update.description()).newLine();
+
+    dropTriggers(apply, baseTableName);
+    addCreateTrigger(apply, updateTriggerName(baseTableName), baseTableName, historyTableName, includedColumns);
+
+    // put a reverted version into the rollback buffer
+    update.toRevertedColumns(includedColumns);
+
+    DdlBuffer rollback = writer.rollback();
+    rollback.append("-- Revert regenerated ").newLine();
+    rollback.append("-- revert changes: ").append(update.description()).newLine();
+    dropTriggers(rollback, baseTableName);
+    addCreateTrigger(rollback, updateTriggerName(baseTableName), baseTableName, historyTableName, includedColumns);
+  }
+
+  private void addCreateTrigger(DdlBuffer apply, String triggerName, String baseTable, String historyTable, List<String> includedColumns) throws IOException {
+
+    // Note that this does not take into account the historyTable name (excepts _history suffix) and
+    // does not take into account excluded columns (all columns included in history)
+    apply
+        .append("create trigger ").append(triggerName).append(" before update,delete on ").append(baseTable)
+        .append(" for each row call \"" + TRIGGER_CLASS + "\";").newLine();
+  }
+
+}