02.1
Classic modefrom, where, orderBy
The declarative shape: a dataset, a predicate tree of field, operator and value, an ordering and a limit. Values can be placeholders the host binds, so the same document serves many callers.
Placeholders
02.2
Pipe modeAn ordered chain of operators
The same query expressed as a stream: filter, then aggregate with a grouping, then sort and limit. Pipe mode exists because some questions are a sequence and forcing them into a single clause tree makes them unreadable.
Operators
02.3
PlanningPushed down, or finished in memory
The planner decides which clauses the database can answer and emits SQL for those. Computed columns, expression filters and the rest are completed by the processor over the returned rows.
Two-stage
02.4
ScopingRequired, and joined
A scope entry marked Required emits its predicate even when a table does not declare the column. ScopeJoins puts the predicate in the ON clause rather than the WHERE, so an out-of-scope row fails the join instead of NULL-padding through a LEFT join.
Multi-tenant
02.5
DatabasesWhatever you already have
The querier interface is the shape database/sql already has, so a pooled or instrumented connection satisfies it as it stands.
database/sql
02.6
ExpressionsThe expression language is yours
Computed columns and expression filters evaluate through an interface. DTL satisfies it directly, which is how the two languages end up in the same field of work.
Pluggable
DTL→02.7
EditorsA grammar and a server
A TextMate grammar under the scope source.dql, and an LSP binary for completion, hover and diagnostics. The server works on a file alone, and a host that knows which datasets and functions exist passes that in for richer completions.
TextMateLSP
Editor support→