This PR implements simple heap-sort approach for query plans like
`SELECT ... FROM t WHERE ... ORDER BY ... LIMIT N` in order to maintain
small set of top N elements in the ephemeral B-tree and avoid sort and
materialization of whole dataset.
I removed all optimizations not related to this particular change in
order to make branch lightweight.
Reviewed-by: Jussi Saurio <jussi.saurio@gmail.com>
Closes#3726
We don't want something like `BEGIN IMMEDIATE` to start a subtransaction,
so instead we will open it if:
- Statement is write, AND
a) Statement has >0 table_references, or
b) The statement is an INSERT (INSERT doesn't track table_references in
the same way as other program types)
1. The number of deferred FK violations when the statement started.
When a statement subtransaction rolls back, the connection's
deferred violation counter will be reset to this value.
2. The number of immediate FK violations that occurred during the
statement. In practice we just need to know whether this number
is nonzero, and if it is, the statement subtransaction will roll
back.
Statement subtransactions will be implemented in future commits.
Rolling back a transaction on Error should result in
`connection.auto_commit` being set back to true.
Added a regression test for this where a UNIQUE constraint violation
rolls back the transaction and trying to COMMIT will fail.
Currently, our default conflict resolution strategy is ROLLBACK, which
ends the transaction. In SQLite, the default is ABORT, which rolls back
the current statement but allows the transaction to continue.
We should migrate to default ABORT once we support subtransactions.
Closes#3746
Reviewed-by: Preston Thorpe <preston@turso.tech>
Closes#3747
Rolling back a transaction should result in `connection.auto_commit` being set
back to true.
Added a regression test for this where a UNIQUE constraint violation rolls back
the transaction and trying to COMMIT will fail.
Currently, our default conflict resolution strategy is ROLLBACK,
which ends the transaction. In SQLite, the default is ABORT, which rolls back
the current statement but allows the transaction to continue.
We should migrate to default ABORT once we support subtransactions.
This patch pushes unsafe Send and Sync to individual components instead
of doing it at Database level. This makes it easier for us to
incrementally fix thread-safety, but avoid developers adding more thread
unsafe code.
op_destroy was assuming we never yield IO from BTreeCursor::btree_destroy(),
so every so often it would just not complete the procedure and leave
dangling pages in the database
We don't need to clear the cursors explicitly because OpenRead and
OpenWrite will anyway replace them.
Reviewed-by: Preston Thorpe <preston@turso.tech>
Closes#3526
The VDBE step() function was taking Arc<MvStore> by value, causing it to
be cloned on every single step of query execution. This resulted in
thousands of atomic reference count increments/decrements per query,
showing up as a major hotspot in profiling.
Changed step() and related functions to take Option<&Arc<MvStore>>
instead, passing a reference rather than cloning the Arc. This eliminates
the unnecessary atomic operations while maintaining the same semantics.
As per SQLite API, sqlite3_reset() does *not* clear bind parameters.
Instead they're persistent across statement reset and only cleared with
sqlite3_clear_bindings().
MVCC is like the annoying younger cousin (I know because I was him) that
needs to be treated differently. MVCC requires us to use root_pages that
might not be allocated yet, and the plan is to use negative root_pages
for that case. Therefore, we need i64 in order to fit this change.
TransitionResult is an internal implementation detail that tells
an invocation of StateMachine::step() to continue looping, but it
is of no use to other callers.
For this reason, just return an IOResult from StateMachine::step()
which simplifies the result handling.
this PR improves 3-6% for `prepare` benchmark without slowing down
others. After this PR we don't have to store `InsnFunction` in
`Program` and `ProgramBuilder` anymore, because `to_function` will
return result without matching.
Reviewed-by: Preston Thorpe <preston@turso.tech>
Closes#3098
