Attached is a patch that does the following:

1) improves performance of commit/rollback by reducing number of round
trips to the server
2) uses 7.1 functionality for setting the transaction isolation level
3) backs out a patch from 11 days ago because that code failed to
compile under jdk1.1

Details:

1)  The old code was doing the following for each commit:
   commit
   begin
   set transaction isolation level xxx
thus a call to commit was performing three round trips to the database.
  The new code does this in one round trip as:
   commit; begin; set transaction isolation level xxx

In a simple test program that performs 1000 transactions (where each
transaction does one simple select inside that transaction) has the
following before and after timings:

Client and Server on same machine

old         new
---         ---
1.877sec    1.405sec   25.1% improvement

Client and Server on different machines
old         new
---         ---
4.184sec    2.927sec   34.3% improvement

(all timings are an average of four different runs)

2)  The driver was using 'set transaction isolation level xxx' at the
begining of each transaction, instead of using the new 7.1 syntax of
'set session characteristics as transaction isolation level xxx' which
only needs to be done once instead of for each transaction.  This is
done conditionally (i.e. if server is 7.0 or older do the old behaviour,
else do the new behaviour) to not break backward compatibility.  This
also required the movement of some code to check/test database version
numbers from the DatabaseMetaData object to the Connection object.

3) Finally while testing, I discovered that the code that was checked in
  11 days ago actually didn't compile.  The code in the patch for
Connection.setCatalog() used Properties.setProperty() which only exists
in JDK1.2 or higher.  Thus compiling the JDBC1 driver failed as this
method doesn't exist.  Thus I backed out that patch.

Barry Lind

diff --git a/src/interfaces/jdbc/org/postgresql/Connection.java b/src/interfaces/jdbc/org/postgresql/Connection.java
index 7c6fb0adba5d2e8f0fd20bed6b12aece9103cce7..1aa7be13f160a73267c5b3e04f8d18dff3dfdc56 100644 (file)
--- a/src/interfaces/jdbc/org/postgresql/Connection.java
+++ b/src/interfaces/jdbc/org/postgresql/Connection.java
@@ -11,7 +11,7 @@ import org.postgresql.util.*;
 import org.postgresql.core.Encoding;
 
 /**
- * $Id: Connection.java,v 1.21 2001/07/30 14:51:19 momjian Exp $
+ * $Id: Connection.java,v 1.22 2001/08/04 19:32:04 momjian Exp $
  *
  * This abstract class is used by org.postgresql.Driver to open either the JDBC1 or
  * JDBC2 versions of the Connection class.
@@ -37,6 +37,9 @@ public abstract class Connection
    */
   private Encoding encoding = Encoding.defaultEncoding();
 
+  private String dbVersionLong;
+  private String dbVersionNumber;
+
   public boolean CONNECTION_OK = true;
   public boolean CONNECTION_BAD = false;
 
@@ -262,18 +265,19 @@ public abstract class Connection
       // used, so we denote this with 'UNKNOWN'.
 
       final String encodingQuery =
-         "select case when pg_encoding_to_char(1) = 'SQL_ASCII' then 'UNKNOWN' else getdatabaseencoding() end";
+         "case when pg_encoding_to_char(1) = 'SQL_ASCII' then 'UNKNOWN' else getdatabaseencoding() end";
 
       // Set datestyle and fetch db encoding in a single call, to avoid making
       // more than one round trip to the backend during connection startup.
 
       java.sql.ResultSet resultSet =
-         ExecSQL("set datestyle to 'ISO'; " + encodingQuery);
+         ExecSQL("set datestyle to 'ISO'; select version(), " + encodingQuery + ";");
 
       if (! resultSet.next()) {
          throw new PSQLException("postgresql.con.failed", "failed getting backend encoding");
       }
-      dbEncoding = resultSet.getString(1);
+      dbVersionLong = resultSet.getString(1);
+      dbEncoding = resultSet.getString(2);
       encoding = Encoding.getEncoding(dbEncoding, info.getProperty("charSet"));
 
       // Initialise object handling
@@ -904,8 +908,7 @@ public abstract class Connection
        if (autoCommit)
            ExecSQL("end");
        else {
-           ExecSQL("begin");
-           doIsolationLevel();
+           ExecSQL("begin; " + getIsolationLevelSQL());
        }
        this.autoCommit = autoCommit;
     }
@@ -934,11 +937,7 @@ public abstract class Connection
     public void commit() throws SQLException {
        if (autoCommit)
            return;
-       ExecSQL("commit");
-       autoCommit = true;
-       ExecSQL("begin");
-       doIsolationLevel();
-       autoCommit = false;
+       ExecSQL("commit; begin; " + getIsolationLevelSQL());
     }
 
     /**
@@ -952,11 +951,7 @@ public abstract class Connection
     public void rollback() throws SQLException {
        if (autoCommit)
            return;
-       ExecSQL("rollback");
-       autoCommit = true;
-       ExecSQL("begin");
-       doIsolationLevel();
-       autoCommit = false;
+       ExecSQL("rollback; begin; " + getIsolationLevelSQL());
     }
 
     /**
@@ -988,7 +983,7 @@ public abstract class Connection
     /**
      * You can call this method to try to change the transaction
      * isolation level using one of the TRANSACTION_* values.
-     *
+     * 
      * <B>Note:</B> setTransactionIsolation cannot be called while
      * in the middle of a transaction
      *
@@ -999,29 +994,67 @@ public abstract class Connection
      * @see java.sql.DatabaseMetaData#supportsTransactionIsolationLevel
      */
     public void setTransactionIsolation(int level) throws SQLException {
-       isolationLevel = level;
-       doIsolationLevel();
+       //In 7.1 and later versions of the server it is possible using
+        //the "set session" command to set this once for all future txns
+        //however in 7.0 and prior versions it is necessary to set it in 
+        //each transaction, thus adding complexity below.
+        //When we decide to drop support for servers older than 7.1
+        //this can be simplified
+        isolationLevel = level;
+        String isolationLevelSQL;
+       switch(isolationLevel) {
+           case java.sql.Connection.TRANSACTION_READ_COMMITTED:
+               if (haveMinimumServerVersion("7.1")) {
+                 isolationLevelSQL = "SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL READ COMMITTED";
+               } else {
+                  isolationLevelSQL = getIsolationLevelSQL();
+                }
+                break;
+
+           case java.sql.Connection.TRANSACTION_SERIALIZABLE:
+               if (haveMinimumServerVersion("7.1")) {
+                 isolationLevelSQL = "SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL SERIALIZABLE";
+               } else {
+                  isolationLevelSQL = getIsolationLevelSQL();
+                }
+                break;
+
+           default:
+               throw new PSQLException("postgresql.con.isolevel",new Integer(isolationLevel));
+       }
+       ExecSQL(isolationLevelSQL);
     }
 
     /**
      * Helper method used by setTransactionIsolation(), commit(), rollback()
-     * and setAutoCommit(). This sets the current isolation level.
+     * and setAutoCommit(). This returns the SQL string needed to
+     * set the isolation level for a transaction.  In 7.1 and later it
+     * is possible to set a default isolation level that applies to all
+     * future transactions, this method is only necesary for 7.0 and older
+     * servers, and should be removed when support for these older
+     * servers are dropped
      */
-    protected void doIsolationLevel() throws SQLException {
+    protected String getIsolationLevelSQL() throws SQLException {
+       //7.1 and higher servers have a default specified so 
+       //no additional SQL is required to set the isolation level
+       if (haveMinimumServerVersion("7.1")) {
+          return "";
+        }
        String q = "SET TRANSACTION ISOLATION LEVEL";
 
        switch(isolationLevel) {
            case java.sql.Connection.TRANSACTION_READ_COMMITTED:
-               ExecSQL(q + " READ COMMITTED");
-               return;
+               q = q + " READ COMMITTED";
+                break;
 
            case java.sql.Connection.TRANSACTION_SERIALIZABLE:
-               ExecSQL(q + " SERIALIZABLE");
-               return;
+               q = q + " SERIALIZABLE";
+                break;
 
            default:
                throw new PSQLException("postgresql.con.isolevel",new Integer(isolationLevel));
        }
+        return q;
     }
 
     /**
@@ -1033,13 +1066,7 @@ public abstract class Connection
      */
     public void setCatalog(String catalog) throws SQLException
     {
-       if(catalog!=null && !catalog.equals(PG_DATABASE)) {
-           close();
-           Properties info=new Properties();
-           info.setProperty("user", PG_USER);
-           info.setProperty("password", PG_PASSWORD);
-           openConnection(PG_HOST, PG_PORT, info, catalog, this_url, this_driver);
-       }
+      //no-op
     }
 
     /**
@@ -1095,4 +1122,31 @@ public abstract class Connection
       return sql;
     }
 
+  /**
+   * What is the version of the server
+   *
+   * @return the database version
+   * @exception SQLException if a database access error occurs
+   */
+  public String getDBVersionNumber() throws SQLException
+  {
+    if(dbVersionNumber == null) {
+      StringTokenizer versionParts = new StringTokenizer(dbVersionLong);
+      versionParts.nextToken(); /* "PostgreSQL" */
+      dbVersionNumber = versionParts.nextToken(); /* "X.Y.Z" */
+    }
+    return dbVersionNumber;
+  }
+
+  public boolean haveMinimumServerVersion(String ver) throws SQLException
+  {
+      if (getDBVersionNumber().compareTo(ver)>=0)
+         return true;
+      else
+         return false;
+  }
+
+
+
 }
+   

diff --git a/src/interfaces/jdbc/org/postgresql/jdbc1/DatabaseMetaData.java b/src/interfaces/jdbc/org/postgresql/jdbc1/DatabaseMetaData.java
index 1df59803dddd41572da2ba1617458121b24f4869..89d195e25df198d7d7badea9fa93953afb8a69d4 100644 (file)
--- a/src/interfaces/jdbc/org/postgresql/jdbc1/DatabaseMetaData.java
+++ b/src/interfaces/jdbc/org/postgresql/jdbc1/DatabaseMetaData.java
@@ -47,15 +47,6 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
   private static final byte defaultRemarks[]="no remarks".getBytes();
 
 
-  private boolean haveMinimumServerVersion(String ver) throws SQLException
-  {
-      if (getDatabaseProductVersion().compareTo(ver)>=0)
-         return true;
-      else
-         return false;
-  }
-
-
   public DatabaseMetaData(Connection conn)
   {
     this.connection = conn;
@@ -126,7 +117,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean nullsAreSortedHigh() throws SQLException
   {
-      return haveMinimumServerVersion("7.2");
+      return connection.haveMinimumServerVersion("7.2");
   }
 
   /**
@@ -159,7 +150,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean nullsAreSortedAtEnd() throws SQLException
   {
-      return ! haveMinimumServerVersion("7.2");
+      return ! connection.haveMinimumServerVersion("7.2");
   }
 
   /**
@@ -182,14 +173,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public String getDatabaseProductVersion() throws SQLException
   {
-       java.sql.ResultSet resultSet = connection.ExecSQL("select version()");
-       resultSet.next();
-
-       StringTokenizer versionParts = new StringTokenizer(resultSet.getString(1));
-       versionParts.nextToken(); /* "PostgreSQL" */
-       String versionNumber = versionParts.nextToken(); /* "X.Y.Z" */
-
-       return versionNumber;
+    return connection.getDBVersionNumber();
   }
 
   /**
@@ -558,7 +542,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean supportsOrderByUnrelated() throws SQLException
   {
-      return haveMinimumServerVersion("6.4");
+      return connection.haveMinimumServerVersion("6.4");
   }
 
   /**
@@ -581,7 +565,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean supportsGroupByUnrelated() throws SQLException
   {
-      return haveMinimumServerVersion("6.4");
+      return connection.haveMinimumServerVersion("6.4");
   }
 
   /**
@@ -608,7 +592,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean supportsLikeEscapeClause() throws SQLException
   {
-    return haveMinimumServerVersion("7.1");
+    return connection.haveMinimumServerVersion("7.1");
   }
 
   /**
@@ -749,7 +733,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean supportsOuterJoins() throws SQLException
   {
-      return haveMinimumServerVersion("7.1");
+      return connection.haveMinimumServerVersion("7.1");
   }
 
   /**
@@ -761,7 +745,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean supportsFullOuterJoins() throws SQLException
   {
-      return haveMinimumServerVersion("7.1");
+      return connection.haveMinimumServerVersion("7.1");
   }
 
   /**
@@ -976,7 +960,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean supportsSelectForUpdate() throws SQLException
   {
-      return haveMinimumServerVersion("6.5");
+      return connection.haveMinimumServerVersion("6.5");
   }
 
   /**
@@ -1053,7 +1037,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean supportsCorrelatedSubqueries() throws SQLException
   {
-      return haveMinimumServerVersion("7.1");
+      return connection.haveMinimumServerVersion("7.1");
   }
 
   /**
@@ -1075,7 +1059,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean supportsUnionAll() throws SQLException
   {
-      return haveMinimumServerVersion("7.1");
+      return connection.haveMinimumServerVersion("7.1");
   }
 
   /**
@@ -1303,7 +1287,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public int getMaxRowSize() throws SQLException
   {
-      if (haveMinimumServerVersion("7.1"))
+      if (connection.haveMinimumServerVersion("7.1"))
          return 1073741824;    // 1 GB
       else
          return 8192;          // XXX could be altered
@@ -1329,7 +1313,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public int getMaxStatementLength() throws SQLException
   {
-      if (haveMinimumServerVersion("7.0"))
+      if (connection.haveMinimumServerVersion("7.0"))
          return 0;             // actually whatever fits in size_t
       else
          return 16384;

diff --git a/src/interfaces/jdbc/org/postgresql/jdbc2/DatabaseMetaData.java b/src/interfaces/jdbc/org/postgresql/jdbc2/DatabaseMetaData.java
index 93e084f5368a18aeeab6cdf8360f9579470a99d5..85ff9ea5ecef9420e4213be68709bfc6a434da6b 100644 (file)
--- a/src/interfaces/jdbc/org/postgresql/jdbc2/DatabaseMetaData.java
+++ b/src/interfaces/jdbc/org/postgresql/jdbc2/DatabaseMetaData.java
@@ -47,15 +47,6 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
   private static final byte defaultRemarks[]="no remarks".getBytes();
 
 
-  private boolean haveMinimumServerVersion(String ver) throws SQLException
-  {
-      if (getDatabaseProductVersion().compareTo(ver)>=0)
-         return true;
-      else
-         return false;
-  }
-
-
   public DatabaseMetaData(Connection conn)
   {
     this.connection = conn;
@@ -126,7 +117,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean nullsAreSortedHigh() throws SQLException
   {
-      return haveMinimumServerVersion("7.2");
+      return connection.haveMinimumServerVersion("7.2");
   }
 
   /**
@@ -159,7 +150,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean nullsAreSortedAtEnd() throws SQLException
   {
-      return ! haveMinimumServerVersion("7.2");
+      return ! connection.haveMinimumServerVersion("7.2");
   }
 
   /**
@@ -182,14 +173,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public String getDatabaseProductVersion() throws SQLException
   {
-       java.sql.ResultSet resultSet = connection.ExecSQL("select version()");
-       resultSet.next();
-
-       StringTokenizer versionParts = new StringTokenizer(resultSet.getString(1));
-       versionParts.nextToken(); /* "PostgreSQL" */
-       String versionNumber = versionParts.nextToken(); /* "X.Y.Z" */
-
-       return versionNumber;
+    return connection.getDBVersionNumber();
   }
 
   /**
@@ -558,7 +542,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean supportsOrderByUnrelated() throws SQLException
   {
-      return haveMinimumServerVersion("6.4");
+      return connection.haveMinimumServerVersion("6.4");
   }
 
   /**
@@ -581,7 +565,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean supportsGroupByUnrelated() throws SQLException
   {
-      return haveMinimumServerVersion("6.4");
+      return connection.haveMinimumServerVersion("6.4");
   }
 
   /**
@@ -608,7 +592,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean supportsLikeEscapeClause() throws SQLException
   {
-    return haveMinimumServerVersion("7.1");
+    return connection.haveMinimumServerVersion("7.1");
   }
 
   /**
@@ -749,7 +733,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean supportsOuterJoins() throws SQLException
   {
-      return haveMinimumServerVersion("7.1");
+      return connection.haveMinimumServerVersion("7.1");
   }
 
   /**
@@ -761,7 +745,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean supportsFullOuterJoins() throws SQLException
   {
-      return haveMinimumServerVersion("7.1");
+      return connection.haveMinimumServerVersion("7.1");
   }
 
   /**
@@ -976,7 +960,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean supportsSelectForUpdate() throws SQLException
   {
-      return haveMinimumServerVersion("6.5");
+      return connection.haveMinimumServerVersion("6.5");
   }
 
   /**
@@ -1053,7 +1037,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean supportsCorrelatedSubqueries() throws SQLException
   {
-      return haveMinimumServerVersion("7.1");
+      return connection.haveMinimumServerVersion("7.1");
   }
 
   /**
@@ -1075,7 +1059,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public boolean supportsUnionAll() throws SQLException
   {
-      return haveMinimumServerVersion("7.1");
+      return connection.haveMinimumServerVersion("7.1");
   }
 
   /**
@@ -1303,7 +1287,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public int getMaxRowSize() throws SQLException
   {
-      if (haveMinimumServerVersion("7.1"))
+      if (connection.haveMinimumServerVersion("7.1"))
          return 1073741824;    // 1 GB
       else
          return 8192;          // XXX could be altered
@@ -1329,7 +1313,7 @@ public class DatabaseMetaData implements java.sql.DatabaseMetaData
    */
   public int getMaxStatementLength() throws SQLException
   {
-      if (haveMinimumServerVersion("7.0"))
+      if (connection.haveMinimumServerVersion("7.0"))
          return 0;             // actually whatever fits in size_t
       else
          return 16384;