SQL extended with transient fields for calculation expressions in enhanced data models
A database language (e.g. SQL) is extended to define a transient field whose value is derived from data stored in a database. The value of the transient field is calculated by the database engine for consumption as needed by the application layer, for example as part of a particular data model. The value of the transient field may not be materialized as a persistent field in the underlying database table, or may be selectively materialized based upon a heuristic or hint. Certain embodiments may implement the transient field as a basic elaboration on standard SQL utilizing an identifier. Some embodiments may implement the transient field as an entity where SQL has been extended to accommodate concepts of a higher-level Entity Relationship Model (ERM). The use of constants and/or floating values (e.g. a current time) in connection with transient fields, is also disclosed.
1. A computer-implemented method comprising:
providing in a database layer, an in-memory database comprising data of a first type and data of a second type;
causing an in-memory database engine to receive from a query engine of an overlying application layer, a query in a database language defining a transient field, wherein the database language is extended to include an entity of an entity-relationship data model (ERM), and the transient field is defined by the entity;
causing the in-memory database engine to communicate with the in-memory database to generate a query result from the query, wherein the in-memory database engine fills in a value for the transient field derived at least in part from the data of the second type; and
causing the in-memory database engine to communicate the query result to the query engine for display to a user;
wherein the value is materialized in a persistent field of the in-memory database based upon a hint from the in-memory database engine, the hint comprising a directive in a declaration of the transient field in the ERM.
2. A computer-implemented method as in claim 1 wherein the database language comprises Structured Query Language (SQL).
3. A computer-implemented method as in claim 1 wherein the transient field is defined by an identifier in the database language.
4. A computer-implemented method as in claim 1 wherein the value is not materialized in a persistent field in the in-memory database.
5. A non-transitory computer readable storage medium embodying a computer program for performing a method, said method comprising:
providing in a database layer, an in-memory database comprising data of a first type and data of a second type;
causing an in-memory database engine to receive from a query engine of an overlying application layer, a query in a database language defining a transient field, wherein the database language is extended to include an entity of an entity-relationship data model (ERM), and the transient field is defined by the entity;
causing the in-memory database engine to communicate with the in-memory database to generate a query result from the query, wherein the in-memory database engine fills in a value for the transient field derived at least in part from the data of the second type;
and causing the in-memory database engine to communicate the query result to the query engine for display to a user;
wherein the value is materialized in a persistent field of the in-memory database based upon a hint from the in-memory database engine, the hint comprising a directive in a declaration of the transient field in the ERM.
6. A non-transitory computer readable storage medium as in claim 5 wherein the database language comprises Structured Query Language (SQL).
7. A non-transitory computer readable storage medium as in claim 5 wherein the transient field is defined by an identifier in the database language.
8. A non-transitory computer readable storage medium as in claim 5 wherein the value is not materialized in a persistent field in the in-memory database.
9. A computer system comprising:
one or more processors;
a software program, executable on said computer system, the software program configured to:
provide in a database layer, an in-memory database comprising data of a first type and data of a second type;
cause an in-memory database engine to receive from a query engine of an overlying application layer, a query in a database language defining a transient field, wherein the database language is extended to include an entity of an entity-relationship data model (ERM), and the transient field is defined by the entity;
cause the in-memory database engine to communicate with the in-memory database to generate a query result from the query, wherein the in-memory database engine fills in a value for the transient field derived at least in part from the data of the second type; and
cause the in-memory database engine to communicate the query result to the query engine for display to a user;
wherein the value is materialized in a persistent field of the in-memory database based upon a hint from the in-memory database engine, the hint comprising a directive in a declaration of the transient field in the ERM.
10. A computer system as in claim 9 wherein the database language comprises Structured Query Language (SQL).
11. A computer system as in claim 9 wherein the transient field is defined by an identifier in the database language.
12. A computer system as in claim 9 wherein the value is not materialized in a persistent field in the in-memory database.