http://docs.openlinksw.com/virtuoso/hooks.html Database Event Hooks OpenLink Virtuoso Universal Server: Documentation virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com 2008-06-20T01:41:44Z OpenLink Software Documentation Team http://docs.openlinksw.com/virtuoso/../images/misc/logo.jpg http://docs.openlinksw.com/virtuoso/fn_dbev_startup.html virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com Database Startup 2008-06-20T01:41:44Z Database Startup DB.DBA.DBEV_STARTUP() If defined, this is called after the server initialization, including roll forward of transaction logs, compilation of stored procedures, etc..., but before starting to listen for clients. Hence this is guaranteed to run before any clients connect or any HTTP messages are serviced. The procedure will run in its own transaction, which will be automatically committed upon return, regardless of run time errors. Result sets are not allowed and return values are discarded. All custom Virtuoso Server Extensions (VSEs) will be defined when calling this procedure. http://docs.openlinksw.com/virtuoso/fn_dbev_connect.html virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com Database Connections 2008-06-20T01:41:44Z Database Connections DB.DBA.DBEV_CONNECT() If defined, this hook is called for each successful ODBC or JDBC connection. The hook is only called after password and license checks have passed. The hook is called before the server acknowledges a successful connect and is therefore guaranteed to run before any other action by the connected client. The function runs in its own transaction, which is automatically committed following successful return. Result sets may not be generated and return values are discarded. The connection_id () and user are defined in the function. SQL states signalled inside this hook will be sent to the client and will cause the connection to be closed server side. http://docs.openlinksw.com/virtuoso/fn_logins.html virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com Database Logins 2008-06-20T01:41:44Z Database Logins DB.DBA.DBEV_LOGIN inout user_name varchar in digest varchar in session_random varchar This function, if defined, will always be called by Virtuoso just before a client is authenticated against the Virtuoso Server. Three parameters are available for audit purposes or any other pre-processing purpose totally user definable. This hook can be used to control how Virtuoso proceeds with the client login by responding to 3 possible return values: http://docs.openlinksw.com/virtuoso/fn_disconnect.html virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com Database Disconnections 2008-06-20T01:41:44Z Database Disconnections DB.DBA.DBEV_DISCONNECT() If defined, this procedure is called after a connection has been found to be disconnected, either as a result of the client process disconnecting, the client process terminating or the server deciding to disconnect, see disconnect_user(). This will also be called if the DBEV_CONNECT hook signals an error, leading to the connection being closed during the connect sequence. All activity on behalf of the disconnecting client is terminated by the time this function is called. This function runs in its own transaction. Result sets are prohibited, return values discarded and errors are logged in the error log file but not otherwise processed. The transaction is committed regardless of errors. The user and connection_id and any connection variables are defined during this hook. http://docs.openlinksw.com/virtuoso/fn_dbev_shutdown.html virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com Database Shutdown 2008-06-20T01:41:44Z Database Shutdown DB.DBA.DBEV_SHUTDOWN() If defined, this function is called when shutting down the server, following disconnection of all clients and making a checkpoint. When a disconnect occurs as a result of server shutdown the DBEV_DISCONNECT hook is not called and this function is expected to perform any logout processing. The rationale is that all disconnect hooks would be called at the same time, creating likely deadlocks, resource contention and there could be no guarantee of time consumed by them or of even whether they would terminate at all. The shutdown will do a checkpoint before calling this hook. This checkpoint will terminate all transactions with a deadlock state. If transactions contain automatic retries, etc..., we cannot guarantee that all activity would have terminated when this hook starts. However, the hook function can try http://docs.openlinksw.com/virtuoso/fn_dbev_prepare.html virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com SQL Statement Preparation 2008-06-20T01:41:44Z SQL Statement Preparation DB.DBA.DBEV_PREPARE(inout tree any) If defined, this function is called after parsing any dynamic SQL statements by any users. The parse tree will be a syntactically correct SQL parse tree. The user and connection variables are defined. The hook should not produce a result set and any return values are discarded. The function runs in the transaction which is current on the connection and the transaction is not automatically committed, so that the hook does not modify application transaction boundaries. The tree may be modified by replacing it with any other correct parse tree or destructively splicing it. The tree is a regular SQL heterogeneous array. If the tree is modified incorrectly, it is probable that the server will crash. http://docs.openlinksw.com/virtuoso/sqlparsetree.html virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com SQL Parse Tree 2008-06-20T01:41:44Z SQL Parse Tree The SQL parse tree is composed of DV_ARRAY_OF_POINTER boxes. Other types of boxes may occur as leaves, where they are interpreted as literals. All nodes' first element (index 0) is the type of the node, one of the constants in sqlparext.h. The nodes' various fields can be accessed through the data members of the sql_tree_t union. Most data members are pointers to the same type. Sometimes they are double pointers, denoting a variable length array of pointers to the struct. The caddr_t type is used to denote a terminal, like a string or other constant. The types are only for declarative value, the entire structure is a self describing, run time typed tree of boxes. The correspondence of the tree to the SQL syntax is documented by the yacc grammar supplied as appendix. http://docs.openlinksw.com/virtuoso/fn_davlogins.html virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com WebDAV Logins 2008-06-20T01:41:44Z WebDAV Logins DB.DBA.DBEV_DAV_LOGIN inout user_name varchar in password varchar in http_auth any This function, if defined, will always be called by Virtuoso just before a HTTP client is authenticated against the WebDAV Server. Three parameters are available for audit purposes or any other pre-processing purpose totally user definable. The data structure of the http_auth is an array containing name/value pairs as described below. http://docs.openlinksw.com/virtuoso/assocauxdata.html virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com Associating Auxiliary Data With A Connection 2008-06-20T01:41:44Z Associating Auxiliary Data With A Connection The following functions allow you to set and retrieve connection variables: