Cache a copy of ResultSetMetaData in the ResultSet.

This solves a major performance problem for ResultSetMetaData users
which did not cache the ResultSetMetaData object.  One of the users
is the driver's own implementation of updatable ResultSets, so this
can't be worked around solely in end user code.

In the 9.0 and earlier releases, the Field objects were used to hold
database lookup results and these were longer lived than the
ResultSetMetaData object.  Now that ResultSetMetaData is holding
these database lookups we must hold onto the object to avoid
repeating the database queries.

Reported as bug #6293, fix by Steven Schlansker.

org/postgresql/jdbc2/AbstractJdbc2ResultSet.java

@@ -80,8 +80,18 @@ public abstract class AbstractJdbc2ResultSet implements BaseResultSet, org.postg
 
     private HashMap columnNameIndexMap; // Speed up findColumn by caching lookups
 
-    public abstract ResultSetMetaData getMetaData() throws SQLException;
+    private ResultSetMetaData rsMetaData;
 
+    protected abstract ResultSetMetaData createMetaData() throws SQLException;
+
+    public ResultSetMetaData getMetaData() throws SQLException
+    {
+        checkClosed();
+        if (rsMetaData == null) {
+            rsMetaData = createMetaData();
+        }
+        return rsMetaData;
+    }
 
     public AbstractJdbc2ResultSet(Query originalQuery, BaseStatement statement, Field[] fields, Vector tuples,
                                   ResultCursor cursor, int maxRows, int maxFieldSize,

org/postgresql/jdbc3/Jdbc3ResultSet.java

@@ -26,9 +26,8 @@ public class Jdbc3ResultSet extends org.postgresql.jdbc3.AbstractJdbc3ResultSet
         super(originalQuery, statement, fields, tuples, cursor, maxRows, maxFieldSize, rsType, rsConcurrency, rsHoldability);
     }
 
-    public java.sql.ResultSetMetaData getMetaData() throws SQLException
+    protected java.sql.ResultSetMetaData createMetaData() throws SQLException
     {
-        checkClosed();
         return new Jdbc3ResultSetMetaData(connection, fields);
     }
 

org/postgresql/jdbc3g/Jdbc3gResultSet.java

@@ -26,9 +26,8 @@ public class Jdbc3gResultSet extends org.postgresql.jdbc3g.AbstractJdbc3gResultS
         super(originalQuery, statement, fields, tuples, cursor, maxRows, maxFieldSize, rsType, rsConcurrency, rsHoldability);
     }
 
-    public java.sql.ResultSetMetaData getMetaData() throws SQLException
+    protected java.sql.ResultSetMetaData createMetaData() throws SQLException
     {
-        checkClosed();
         return new Jdbc3gResultSetMetaData(connection, fields);
     }
 

org/postgresql/jdbc4/Jdbc4ResultSet.java

@@ -26,9 +26,8 @@ public class Jdbc4ResultSet extends AbstractJdbc4ResultSet implements java.sql.R
         super(originalQuery, statement, fields, tuples, cursor, maxRows, maxFieldSize, rsType, rsConcurrency, rsHoldability);
     }
 
-    public java.sql.ResultSetMetaData getMetaData() throws SQLException
+    protected java.sql.ResultSetMetaData createMetaData() throws SQLException
     {
-        checkClosed();
         return new Jdbc4ResultSetMetaData(connection, fields);
     }