High performance real-time relational database system and methods for using same
A database system supporting persistent queries, comprising a persistent query service that receives connections and requests from client software applications; and a plurality of network-attached data sources; and a method for providing persistent queries using a persistent query service.
1. A database system supporting persistent queries, the system comprising:
a persistent query service stored and operating on a computer adapted to receive connections and requests from client software applications;
wherein, on receiving a request to create a persistent query from a client software application, the persistent query service:
creates a query virtual table corresponding to the persistent query; parses the persistent query to create a tree structure representing a logical arrangement of a plurality of operators that yield results required by the persistent query;
creates a plurality of intermediate virtual tables corresponding to the plurality of operators, wherein creating each intermediate virtual table further comprises establishing listeners associated with the respective intermediate virtual table to receive data change notifications;
establishes listeners for the query virtual table to receive data change notifications from the plurality of intermediate virtual tables;
creates a plurality of data source virtual tables, each corresponding to a specific data source required to fulfill the persistent query; wherein each respective data source is drawn from a plurality of data sources;
causes the plurality of data source virtual tables to retrieve initial data from the plurality of data sources; and
propagates data via the plurality of intermediate virtual tables and their associated listeners to the persistent query virtual table; and
wherein, on detection of a data change in a first data source, the data source virtual table associated with the first data source invokes a plurality of corresponding methods of listeners of the plurality of intermediate virtual tables and propagates the data change via the plurality of intermediate virtual tables and their associated listeners to the persistent query virtual table, and the client software application executes the client code of at least one affected listener.
2. A method for creating and using persistent queries in a database system, comprising the steps of:
creating, at a persistent query service stored and operating on a computer, via a request received from a software application, a persistent query; wherein the step of creating the persistent query further comprises establishing listeners with client code to receive notifications from the persistent query;
creating a query virtual table corresponding to the persistent query;
parsing the persistent query to create a tree structure representing a logical arrangement of a plurality of operators that yield results required by the persistent query;
creating a plurality of intermediate virtual tables corresponding to the plurality of operators; wherein creating each intermediate virtual table further comprises establishing listeners associated with the respective intermediate virtual table to receive data change notifications;
establishing listeners for the query virtual table to receive data change notifications from the plurality of intermediate virtual tables;
creating a plurality of data source virtual tables, each corresponding to a specific data source required to fulfill the persistent query; wherein each respective data source is drawn from a plurality of data sources;
retrieving, by the plurality of data source virtual tables, initial data from the plurality of data sources;
invoking, by the plurality of data source virtual tables, row added methods of the plurality of intermediate virtual tables;
propagating data via the plurality of intermediate virtual tables and their associated listeners to the persistent query virtual table;
on detection of a data change in a first data source, invoking by the data source virtual table associated with the first data source corresponding methods of listeners of the plurality of intermediate virtual tables;
propagating the data change via the plurality of intermediate virtual tables and their associated listeners to the persistent query virtual table; and
executing the client code of each affected listener in the query virtual table.