We'd like this to be part of the query syntax itself, but doing so
requires extending DataScript's parser.
Instead we generalize our `args` to `options`, and take `:limit`
and `:order-by-vars`. The former must be an integer or nil, and the
latter is an array of `[var direction]` pairs.
This commit includes descriptive error messages and tests for success
and failure.
This caches a partition map per DB, which is helpful because it exposes
what the point in time DB partition state is, but is unhelpful because
the partition state can advance underneath the DB cache. This is
generally true of the approach -- this can happen to the ident/entid
maps, and the datoms themselves -- so we'll roll with it for now.
This reduces the number of SQL UPDATE operations from linear in the
number of id-literals used to constant in the number of known
partitions.
* Alter how clauses are concatenated. They now preserve order more accurately.
* Track mappings between vars and extracted type columns.
* Generate type code constraints.
* Push known types down into :not.
* Push known types down into :or.
* Tests and test fixes.
Note that `go` (and `go-pair`) don't descend into `for` comprehensions
and other situations in which a fn is created. This commit rewrites to
use nested `loop`s, and also improves use of `<av`.
* Batch up datoms into a smaller number of queries, improving transact speed by about 50%.
* Restore transacting FTS attributes.
* Implement retraction of freetext datoms.
This is almost complete; it passes the test suite save for retracting
fulltext datoms correctly.
There's a lot to say about this approach, but I don't have time to give
too many details. The broad outline is as follows. We collect datoms
to add and retract in a tx_lookup table. Depending on flags ("search
value" sv and "search value type tag" svalue_type_tag) we "complete" the
tx_lookup table by joining matching datoms. This allows us to find
datoms that are present (and should not be added as part of the
transaction, or should be retracted as part of the transaction, or
should be replaced as part of the transaction. We complete the
tx_lookup (in place!) in two separate INSERTs to avoid a quadratic
two-table walk (explain the queries to observe that both INSERTs walk
the lookup table once and then use the datoms indexes to complete the
matching values).
We could simplify the code by using multiple lookup tables, both for the
two cases of search parameters (eav vs. ea) and for the incomplete and
completed rows. Right now we differentiate the former with NULL checks,
and the latter by incrementing the added0 column. It performs well
enough, so I haven't tried to understand the performance of separating
these things.
After the tx_lookup table is completed, we build the transaction from
it; and update the datoms materialized view table as well. Observe the
careful handling of the "search value" sv parameters to handle replacing
:db.cardinality/one datoms.
Finally, we read the processed transaction back to produce to the API.
This is strictly to match the Datomic API; we might make allow to skip
this, since many consumers will not want to stream this over the wire.
Rough timings show the transactor processing a single >50k datom
transaction in about 3.5s, of which less than 0.5s is spent in the
expensive joins. Further, repeating the processing of the same
transaction is only about 3.5s again! That's the worst possible for the
joins, since every single inserted datom will already be present in the
database, making the most expensive join match every row.
