From ae79dd92ec5a1fe706223307fa5a5edf7df902ff Mon Sep 17 00:00:00 2001
From: Roland Praml <roland.praml@foconis.de>
Date: Fri, 7 Jan 2022 14:26:21 +0100
Subject: [PATCH] DB2: Experimental: Add QueryPlanLogger for DB2

---
 .../server/core/InternalConfiguration.java    |  2 +
 .../server/query/QueryPlanLoggerDb2.java      | 55 +++++++++++++++++++
 2 files changed, 57 insertions(+)
 create mode 100644 ebean-core/src/main/java/io/ebeaninternal/server/query/QueryPlanLoggerDb2.java

diff --git a/ebean-core/src/main/java/io/ebeaninternal/server/core/InternalConfiguration.java b/ebean-core/src/main/java/io/ebeaninternal/server/core/InternalConfiguration.java
index dc24cfdc4..d1146ac15 100644
--- a/ebean-core/src/main/java/io/ebeaninternal/server/core/InternalConfiguration.java
+++ b/ebean-core/src/main/java/io/ebeaninternal/server/core/InternalConfiguration.java
@@ -597,6 +597,8 @@ public final class InternalConfiguration {
         return new QueryPlanLoggerSqlServer();
       case ORACLE:
         return new QueryPlanLoggerOracle();
+      case DB2:
+        return new QueryPlanLoggerDb2();
       default:
         return new QueryPlanLoggerExplain();
     }
diff --git a/ebean-core/src/main/java/io/ebeaninternal/server/query/QueryPlanLoggerDb2.java b/ebean-core/src/main/java/io/ebeaninternal/server/query/QueryPlanLoggerDb2.java
new file mode 100644
index 000000000..4b892f987
--- /dev/null
+++ b/ebean-core/src/main/java/io/ebeaninternal/server/query/QueryPlanLoggerDb2.java
@@ -0,0 +1,55 @@
+
+package io.ebeaninternal.server.query;
+
+import io.ebeaninternal.api.CoreLog;
+import io.ebeaninternal.api.SpiDbQueryPlan;
+import io.ebeaninternal.api.SpiQueryPlan;
+import io.ebeaninternal.server.type.bindcapture.BindCapture;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.Random;
+
+/**
+ * A QueryPlanLogger for DB2.
+ * 
+ * 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();
+  @Override
+  public SpiDbQueryPlan collectPlan(Connection conn, SpiQueryPlan plan, BindCapture bind) {
+    try (Statement stmt = conn.createStatement()) {
+      int queryNo = rnd.nextInt(Integer.MAX_VALUE);
+      try (PreparedStatement explainStmt = conn
+          .prepareStatement("EXPLAIN PLAN SET QUERYNO=" + queryNo + " FOR " + plan.getSql())) {
+        bind.prepare(explainStmt, conn);
+        explainStmt.execute();
+      }
+
+      try (ResultSet rset = stmt.executeQuery("select * from EXPLAIN_STATEMENT where QUERYNO=" + queryNo)) {
+        return readQueryPlan(plan, bind, rset);
+      }
+    } catch (SQLException e) {
+      CoreLog.log.warn("Could not log query plan", e);
+      return null;
+    }
+  }
+
+}