Mercurial > hg > monetdb-java

comparison src/main/java/nl/cwi/monetdb/jdbc/MonetConnection.java @ 215:71b039bc2d99

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Added support for querying the sys.comments table for some meta data methods when connected to a MonetDB server which has table sys.comments.
author Martin van Dinther <martin.van.dinther@monetdbsolutions.com>
date Thu, 19 Apr 2018 16:13:01 +0200 (2018-04-19)
parents b8c007e86694
children 4572f0694fde
comparison
equal deleted inserted replaced
214:b8c007e86694 215:71b039bc2d99
145 /** Whether or not BLOB is mapped to Types.VARBINARY instead of Types.BLOB within this connection */ 145 /** Whether or not BLOB is mapped to Types.VARBINARY instead of Types.BLOB within this connection */
146 private boolean treatBlobAsVarBinary = false; 146 private boolean treatBlobAsVarBinary = false;
147 /** Whether or not CLOB is mapped to Types.VARCHAR instead of Types.CLOB within this connection */ 147 /** Whether or not CLOB is mapped to Types.VARCHAR instead of Types.CLOB within this connection */
148 private boolean treatClobAsVarChar = false; 148 private boolean treatClobAsVarChar = false;
149 149
150 // Internal cache for determining if system table sys.comments (new as of Mar2018 release) exists on server
151 private boolean queriedCommentsTable = false;
152 private boolean hasCommentsTable = false;
153
154
150 /** 155 /**
151 * Constructor of a Connection for MonetDB. At this moment the 156 * Constructor of a Connection for MonetDB. At this moment the
152 * current implementation limits itself to storing the given host, 157 * current implementation limits itself to storing the given host,
153 * database, username and password for later use by the 158 * database, username and password for later use by the
154 * createStatement() call. This constructor is only accessible to 159 * createStatement() call. This constructor is only accessible to
1666 * This allows generic JDBC programs to fetch Clob data via getString() 1671 * This allows generic JDBC programs to fetch Clob data via getString()
1667 * instead of getClob() and Clob.getCharacterStream() to reduce overhead. 1672 * instead of getClob() and Clob.getCharacterStream() to reduce overhead.
1668 */ 1673 */
1669 boolean mapClobAsVarChar() { 1674 boolean mapClobAsVarChar() {
1670 return treatClobAsVarChar; 1675 return treatClobAsVarChar;
1676 }
1677
1678 /**
1679 * Internal utility method to query the server to find out if it has
1680 * the system table sys.comments (which is new as of Mar2018 release).
1681 * The result is cached and reused, so that we only test the query once per connection.
1682 * This method is used by methods from MonetDatabaseMetaData.
1683 */
1684 boolean commentsTableExists() {
1685 if (queriedCommentsTable)
1686 return hasCommentsTable;
1687
1688 queriedCommentsTable = true; // set flag, so the querying part below is done only once, at first invocation.
1689 Statement stmt = null;
1690 ResultSet rs = null;
1691 try {
1692 stmt = createStatement();
1693 if (stmt != null) {
1694 rs = stmt.executeQuery( "SELECT \"id\", \"remark\" FROM \"sys\".\"comments\" LIMIT 1");
1695 if (rs != null) {
1696 rs.next();
1697 hasCommentsTable = true;
1698 }
1699 }
1700 } catch (SQLException se) {
1701 /* ignore */
1702 } finally {
1703 if (rs != null) {
1704 try {
1705 rs.close();
1706 } catch (SQLException e) { /* ignore */ }
1707 }
1708 if (stmt != null) {
1709 try {
1710 stmt.close();
1711 } catch (SQLException e) { /* ignore */ }
1712 }
1713 }
1714 // for debug: System.out.println("commentsTableExists returns: " + hasCommentsTable);
1715 return hasCommentsTable;
1671 } 1716 }
1672 1717
1673 /** 1718 /**
1674 * Sends the given string to MonetDB as special transaction command. 1719 * Sends the given string to MonetDB as special transaction command.
1675 * All possible returned information is discarded. 1720 * All possible returned information is discarded.