A practical theory of language-integrated query

Abstract

Language-integrated query is receiving renewed attention, in part because of its support through Microsoft's LINQ framework. We present a practical theory of language-integrated query based on quotation and normalisation of quoted terms. Our technique supports join queries, abstraction over values and predicates, composition of queries, dynamic generation of queries, and queries with nested intermediate data. Higher-order features prove useful even for constructing first-order queries. We prove a theorem characterising when a host query is guaranteed to generate a single SQL query. We present experimental results confirming our technique works, even in situations where Microsoft's LINQ framework either fails to produce an SQL query or, in one case, produces an avalanche of SQL queries.

FuzzyVariantsExplorer: Graded exploration of genomic data and fuzzy queries

“…Several SQL queries in the source code have been written in Quill [12] a quoted domain specific language created by a Twitter software engineer. It has been inspired by a paper about language-integrated queries [13] and it allows for compile-time query generation and asynchronous execution, a modality well accepted in the Play2's share-nothing architecture based on actors.…”

A step towards genuine declarative language-integrated queries

“…However, in the context of LINQ to SQL, the problem of analysing and normalising of LINQ queries in order to provide minimal and cohesive mapping to SQL has drawn attention of the scientific community. This is caused mostly by some drawbacks of the original Microsoft's solution that in some cases may fail or produce a so-called "query avalanche" [18] [19].…”

Ur/Web

“…However, Links pioneered many of the other design elements on display in Figure 1, including type-safe combination of HTML and database code within a single language. One further key difference is that Ur/Web works with direct embedding of SQL code, whereas Links compiles to SQL from a subset of itself, presented as a monadic query language [7].…”

“…The language-integrated query approach represents queries within a restricted subset of the host programming language, rather than working with explicit embedded syntax of a language like SQL. Microsoft's LINQ [27] is the well-known example that gives the approach its name, but the contemporaneous Links language [7,11] uses static type checking and term rewriting to provide more principled guarantees about which expressions will compile to SQL successfully. Ur/Web encodes SQL as a library, with no special type-inference support required in the compiler, and the programmer benefits from the explicit control over exactly which code will be passed to the database system.…”

“…The Links project [7,11] pioneered the "tierless programming" approach, combining all the pieces of dynamic Web applications within one statically typed functional language. More recent designs in the mainstream reap some similar benefits, as in Google's Web Toolkit 1 and Closure 2 systems, for adding compilation on top of Web-standard languages; and Microsoft's LINQ [27], for typesafe querying (to SQL databases and more) within general-purpose languages.…”