35d73d5541
This adds an `:order` keyword to `:find`. If present, the results of the query will be an ordered set, rather than an unordered set; rows will appear in an ordered defined by each `:order` entry. Each can be one of three things: - A var, `?x`, meaning "order by ?x ascending". - A pair, `(asc ?x)`, meaning "order by ?x ascending". - A pair, `(desc ?x)`, meaning "order by ?x descending". Values will be ordered in this sequence for asc, and in reverse for desc: 1. Entity IDs, in ascending numerical order. 2. Booleans, false then true. 3. Timestamps, in ascending numerical order. 4. Longs and doubles, intermixed, in ascending numerical order. 5. Strings, in ascending lexicographic order. 6. Keywords, in ascending lexicographic order, considering the entire ns/name pair as a single string separated by '/'. Subcommits: Pre: make bound_value public. Pre: generalize ErrorKind::UnboundVariable for use in order. Part 1: parse (direction, var) pairs. Part 2: parse :order clause into FindQuery. Part 3: include order variables in algebrized query. We add order variables to :with, so we can reuse its type tag projection logic, and so that we can phrase ordering in terms of variables rather than datoms columns. Part 4: produce SQL for order clauses. |
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This crate turns an algebrized Datalog query into a domain-specific representation of a SQL query, and then uses mentat_sql to turn that into a SQL string to be executed.
This subsumes both planning and query construction, because in Mentat the SQL query is effectively a query plan.