3 ms·

I noticed that the analyzer's schema includes an analyzer revision, presumably as a way to allow newer analyzers to be re-run against older versions of the code

I noticed that the analyzer's schema includes an analyzer revision, presumably as a way to allow newer analyzers to be re-run against older versions of the code. This raises a question for Rich regarding Datomic and the notion of "derived facts" a la "Out Of The Tar Pit": Datalog Rules can be used to query by some trivial notion of derived facts at any point in time, but most derived facts are expensive to compute and thus should be cached and introduced by a new transaction. In the case of Codeq, this includes the full output of the analyzer. It seems like a natural extension of Datomic to support lazy calculation and caching of derived facts. I could even imagine some cluster scheduling of that work, in a sense producing a map-reduced immutable materialized view of sorts. I realize I said a question was coming, but I'm having a hard time formulating one... which probably means that I don't understand the problem well enough. So, can you talk a little bit about how you envision Datomic evolving with respect to derived facts?

richhickey 14y ago
We don't have any support for materialized views at present, but they are on the list of enhancements to consider.
- rjn945 14y ago
  Obligatory Wikipedia link for those of us (like me) who don't know what materialized views are: http://en.wikipedia.org/wiki/Materialized_view http://en.wikipedia.org/wiki/Materialized_view In short: "In a database management system following the relational model, a view is a virtual table representing the result of a database query. Whenever a query or an update addresses an ordinary view's virtual table, the DBMS converts these into queries or updates against the underlying base tables. A materialized view takes a different approach in which the query result is cached as a concrete table that may be updated from the original base tables from time to time. This enables much more efficient access, at the cost of some data being potentially out-of-date. It is most useful in data warehousing scenarios, where frequent queries of the actual base tables can be extremely expensive."

richhickey 14y ago

We don't have any support for materialized views at present, but they are on the list of enhancements to consider.

rjn945 14y ago
Obligatory Wikipedia link for those of us (like me) who don't know what materialized views are: http://en.wikipedia.org/wiki/Materialized_view http://en.wikipedia.org/wiki/Materialized_view In short: "In a database management system following the relational model, a view is a virtual table representing the result of a database query. Whenever a query or an update addresses an ordinary view's virtual table, the DBMS converts these into queries or updates against the underlying base tables. A materialized view takes a different approach in which the query result is cached as a concrete table that may be updated from the original base tables from time to time. This enables much more efficient access, at the cost of some data being potentially out-of-date. It is most useful in data warehousing scenarios, where frequent queries of the actual base tables can be extremely expensive."