FEATURE: NEW: QueryPlanLogger for DB2

ebean-api/src/main/java/io/ebean/DatabaseBuilder.java

@@ -2079,6 +2079,11 @@ default DatabaseBuilder queryPlanEnable(boolean queryPlanEnable) {
   @Deprecated
   DatabaseBuilder setQueryPlanEnable(boolean queryPlanEnable);
 
+  /**
+   * Set platform specific query plan options.
+   */
+  public void setQueryPlanOptions(String queryPlanOptions);
+
   /**
    * Set the query plan collection threshold in microseconds.
    * <p>
@@ -3061,6 +3066,11 @@ interface Settings extends DatabaseBuilder {
      */
     boolean isQueryPlanEnable();
 
+    /**
+     * Returns platform specific query plan options.
+     */
+    public String getQueryPlanOptions();
+
     /**
      * Return the query plan collection threshold in microseconds.
      */

ebean-api/src/main/java/io/ebean/config/DatabaseConfig.java

@@ -511,6 +511,11 @@ public class DatabaseConfig implements DatabaseBuilder.Settings {
    */
   private boolean queryPlanEnable;
 
+  /**
+   * Additional platform specific options for query-plan generation.
+   */
+  private String queryPlanOptions;
+
   /**
    * The default threshold in micros for collecting query plans.
    */
@@ -2146,6 +2151,7 @@ protected void loadSettings(PropertiesWrapper p) {
     queryPlanTTLSeconds = p.getInt("queryPlanTTLSeconds", queryPlanTTLSeconds);
     slowQueryMillis = p.getLong("slowQueryMillis", slowQueryMillis);
     queryPlanEnable = p.getBoolean("queryPlan.enable", queryPlanEnable);
+    queryPlanOptions = p.get("queryPlan.options", queryPlanOptions);
     queryPlanThresholdMicros = p.getLong("queryPlan.thresholdMicros", queryPlanThresholdMicros);
     queryPlanCapture = p.getBoolean("queryPlan.capture", queryPlanCapture);
     queryPlanCapturePeriodSecs = p.getLong("queryPlan.capturePeriodSecs", queryPlanCapturePeriodSecs);
@@ -2461,6 +2467,25 @@ public DatabaseConfig setQueryPlanEnable(boolean queryPlanEnable) {
     return this;
   }
 
+  /**
+   * Returns platform specific query plan options.
+   */
+  @Override
+  public String getQueryPlanOptions() {
+    return queryPlanOptions;
+  }
+
+  /**
+   * Set platform specific query plan options.
+   */
+  @Override
+  public void setQueryPlanOptions(String queryPlanOptions) {
+    this.queryPlanOptions = queryPlanOptions;
+  }
+
+  /**
+   * Return the query plan collection threshold in microseconds.
+   */
   @Override
   public long getQueryPlanThresholdMicros() {
     return queryPlanThresholdMicros;

ebean-core/src/main/java/io/ebeaninternal/server/core/InternalConfiguration.java

@@ -595,6 +595,8 @@ QueryPlanLogger queryPlanLogger(Platform platform) {
         return new QueryPlanLoggerSqlServer();
       case ORACLE:
         return new QueryPlanLoggerOracle();
+      case DB2:
+        return new QueryPlanLoggerDb2(config.getQueryPlanOptions());
       case POSTGRES:
         return new QueryPlanLoggerExplain("explain (analyze, buffers) ");
       case YUGABYTE:

ebean-core/src/main/java/io/ebeaninternal/server/query/QueryPlanLoggerDb2.java

@@ -0,0 +1,122 @@
+
+package io.ebeaninternal.server.query;
+
+import io.ebean.util.IOUtils;
+import io.ebean.util.StringHelper;
+import io.ebeaninternal.api.CoreLog;
+import io.ebeaninternal.api.SpiDbQueryPlan;
+import io.ebeaninternal.api.SpiQueryPlan;
+import io.ebeaninternal.server.bind.capture.BindCapture;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.Map;
+import java.util.Random;
+
+import static java.lang.System.Logger.Level.WARNING;
+
+/**
+ * A QueryPlanLogger for DB2.
+ * <p>
+ * To use query plan capturing, you have to install the explain tables with
+ * <code>SYSPROC.SYSINSTALLOBJECTS( 'EXPLAIN', 'C' , '', CURRENT SCHEMA )</code>.
+ * To do this in a repeatable script, you may use this statement:
+ *
+ * <pre>
+ * BEGIN
+ * IF NOT EXISTS (SELECT * FROM SYSCAT.TABLES WHERE TABSCHEMA = CURRENT SCHEMA AND TABNAME = 'EXPLAIN_STREAM') THEN
+ *    call SYSPROC.SYSINSTALLOBJECTS( 'EXPLAIN', 'C' , '', CURRENT SCHEMA );
+ * END IF;
+ * END
+ * </pre>
+ *
+ * @author Roland Praml, FOCONIS AG
+ */
+public final class QueryPlanLoggerDb2 extends QueryPlanLogger {
+
+  private Random rnd = new Random();
+
+  private final String schema;
+
+  private final boolean create;
+
+  private static final String GET_PLAN_TEMPLATE = readReasource("QueryPlanLoggerDb2.sql");
+
+  private static final String CREATE_TEMPLATE = "BEGIN\n"
+    + "IF NOT EXISTS (SELECT * FROM SYSCAT.TABLES WHERE TABSCHEMA = ${SCHEMA} AND TABNAME = 'EXPLAIN_STREAM') THEN\n"
+    + "  CALL SYSPROC.SYSINSTALLOBJECTS( 'EXPLAIN', 'C' , '', ${SCHEMA} );\n"
+    + "END IF;\n"
+    + "END";
+
+  public QueryPlanLoggerDb2(String opts) {
+    Map<String, String> map = StringHelper.delimitedToMap(opts, ";", "=");
+    create = !"false" .equals(map.get("create")); // default is create
+    String schema = map.get("schema"); // should be null or SYSTOOLS
+    if (schema == null || schema.isEmpty()) {
+      this.schema = null;
+    } else {
+      this.schema = schema.toUpperCase();
+    }
+  }
+
+  private static String readReasource(String resName) {
+    try (InputStream stream = QueryPlanLoggerDb2.class.getResourceAsStream(resName)) {
+      if (stream == null) {
+        throw new IllegalStateException("Could not find resource " + resName);
+      }
+      BufferedReader reader = IOUtils.newReader(stream);
+      StringBuilder sb = new StringBuilder();
+      reader.lines().forEach(line -> sb.append(line).append('\n'));
+      return sb.toString();
+    } catch (IOException e) {
+      throw new IllegalStateException("Could not read resource " + resName, e);
+    }
+  }
+
+  @Override
+  public SpiDbQueryPlan collectPlan(Connection conn, SpiQueryPlan plan, BindCapture bind) {
+    try (Statement stmt = conn.createStatement()) {
+      if (create) {
+        // create explain tables if neccessary
+        if (schema == null) {
+          stmt.execute(CREATE_TEMPLATE.replace("${SCHEMA}", "CURRENT USER"));
+        } else {
+          stmt.execute(CREATE_TEMPLATE.replace("${SCHEMA}", "'" + schema + "'"));
+        }
+        conn.commit();
+      }
+
+      try {
+        int queryNo = rnd.nextInt(Integer.MAX_VALUE);
+
+        String sql = "EXPLAIN PLAN SET QUERYNO = " + queryNo + " FOR " + plan.sql();
+        try (PreparedStatement explainStmt = conn.prepareStatement(sql)) {
+          bind.prepare(explainStmt, conn);
+          explainStmt.execute();
+        }
+
+        sql = schema == null
+          ? GET_PLAN_TEMPLATE.replace("${SCHEMA}", conn.getMetaData().getUserName().toUpperCase())
+          : GET_PLAN_TEMPLATE.replace("${SCHEMA}", schema);
+
+        try (PreparedStatement pstmt = conn.prepareStatement(sql)) {
+          pstmt.setInt(1, queryNo);
+          try (ResultSet rset = pstmt.executeQuery()) {
+            return readQueryPlan(plan, bind, rset);
+          }
+        }
+      } finally {
+        conn.rollback(); // do not keep query plans in DB
+      }
+    } catch (SQLException e) {
+      CoreLog.log.log(WARNING, "Could not log query plan", e);
+      return null;
+    }
+  }
+}