This PR adds the beginnings of
[AUTOVACUUM](https://www.sqlite.org/lang_vacuum.html) to Limbo. It adds
a feature flag called `omit_autovacuum` which is analogous to
`SQLITE_OMIT_AUTOVACUUM`. It is off by default, same as SQLite.
It introduces the concept of [pointer map pages](https://www.sqlite.org/
fileformat.html#pointer_map_or_ptrmap_pages) which are reverse index
pages used to map pages to their parents. This is used to swap pages
(when a table is deleted for instance) to keep root pages clustered at
the beginning of the file. It's also used while creating a table to
ensure that root pages are clustered at the beginning (although, this
isn't completely implemented yet)
Finally, it also adds a couple of missing instructions like `Int64` that
are required for `PRAGMA` commands related to `auto_vacuum` settings
<img width="1512" alt="Screenshot 2025-05-28 at 8 47 51 PM"
src="https://github.com/user-
attachments/assets/d52eb74f-5b79-4d52-9401-1bdc2dcc304d" />
Closes#1600
This PR implements the `ToSqlString` trait to most of the `ast` structs
and to the `SelectPlan`, `UpdatePlan`, `DeletePlan`,
`CompoundSelectPlan`.
Inside the files in the `to_sql_string` folder, I annotated many `TODOs`
with things that seem to diverge from SQLite syntax. The most egregious
by far was that Create Trigger statements do not use the standard
`delete`, `select`, `update`, and `insert` statements. The parser uses
different structs for those statements only in Create Trigger. E.g
`ast::TriggerCmdUpdate` instead of `ast::Update` and so on.
Also, as this iteration of reverse parsing is not particularly efficient
in the number of string allocations it does. I tested different methods
of achieving this by using `format!`, pushing directly to a `String`, or
just pushing to `Vec<String>` and joining all the string with a space
separator. I focused mainly on trying to get the syntax to print
correctly without major hurdles in understanding the code.
Lastly, I intend in the future to use this code in the simulator to
expand the its available syntax.
Closes#1619
This commit ensures that the metadata in the database header and the pointer map pages allocated are correctly persisted to the page cache. This was not being done earlier.
This commit introduces AUTOVACUUM to Limbo. It introduces the concept of ptrmap pages and also adds some additional instructions that are required to make AUTOVACUUM PRAGMA work
This PR adds support for table-valued functions for PRAGMAs (see the
[PRAGMA functions section](https://www.sqlite.org/pragma.html)).
Additionally, it introduces built-in table-valued functions. I
considered using extensions for this, but there are several reasons in
favor of a dedicated mechanism:
* It simplifies the use of internal functions, structs, etc. For
example, when implementing `json_each` and `json_tree`, direct access to
internals was necessary:
https://github.com/tursodatabase/limbo/pull/1088
* It avoids FFI overhead. [Benchmarks](https://github.com/piotrrzysko/li
mbo/blob/pragma_vtabs_bench/core/benches/pragma_benchmarks.rs) on my
hardware show that `pragma_table_info()` implemented as an extension is
2.5× slower than the built-in version.
Reviewed-by: Jussi Saurio <jussi.saurio@gmail.com>
Closes#1642
In preparation for `CREATE VIEW`, we need to have the original sql query
that was used to create the view. I'm using the scanner's offset to
slice into the original input, trimming the newlines, and passing it to
the translate function.
Reviewed-by: Jussi Saurio <jussi.saurio@gmail.com>
Closes#1621
Again found when fuzzing nested where clause subqueries:
Aggregate registers need to be NULLed at the start because the same
registers might be reused on another invocation of a subquery, and if
they are not NULLed, the 2nd invocation of the same subquery will have
values left over from the first invocation.
Reviewed-by: Preston Thorpe (@PThorpe92)
Closes#1614
- TableReferences struct, which holds both:
- joined_tables, and
- outer_query_refs
- JoinedTable:
- this is just a rename of the previous TableReference struct
- OuterQueryReference
- this is to distinguish from JoinedTable those cases where
e.g. a subquery refers to an outer query's table, or a CTE
refers to a previous CTE.
Both JoinedTable and OuterQueryReference can be referred to by expressions,
but only JoinedTables are considered for join ordering optimization and so
forth.
This commit does not compile.
Currently we have this:
program.alloc_cursor_id(Option<String>, CursorType)`
where the String is the table's name or alias ('users' or 'u' in
the query).
This is problematic because this can happen:
`SELECT * FROM t WHERE EXISTS (SELECT * FROM t)`
There are two cursors, both with identifier 't'. This causes a bug
where the program will use the same cursor for both the main query
and the subquery, since they are keyed by 't'.
Instead introduce `CursorKey`, which is a combination of:
1. `TableInternalId`, and
2. index name (Option<String> -- in case of index cursors.
This should provide key uniqueness for cursors:
`SELECT * FROM t WHERE EXISTS (SELECT * FROM t)`
here the first 't' will have a different `TableInternalId` than the
second `t`, so there is no clash.
Currently in the main translation logic after planning and optimization,
we don't _really_ need to pass a `&mut Vec<WhereTerm>` around anymore,
except for the fact that virtual table constraint resolution is done ad-
hoc in `init_loop()`.
Even there, the only thing we mutate is `WhereTerm::consumed` which is a
boolean indicating that the term has been "used up" by the optimizer and
shouldn't be evaluated as a normal where clause condition anymore.
In the upcoming branch for WHERE clause subqueries, I want to store
immutable references to WHERE clause expressions in `Resolver`, but this
is unfortunately not possible if we still use the aforementioned mutable
references.
Hence, we can temporarily make `WhereTerm::consumed` a `Cell<bool>`
which allows us to pass an immutable reference to `init_loop()`, and the
`Cell` can be removed once the virtual table constraint resolution is
moved to an earlier part of the query processing pipeline.
Closes#1597
Currently in the main translation logic after planning and optimization,
we don't _really_ need to pass a &mut Vec<WhereTerm> around anymore, except
for the fact that virtual table constraint resolution is done ad-hoc in
`init_loop()`. Even there, the only thing we mutate is `WhereTerm::consumed`
which is a boolean indicating that the term has been "used up" by the optimizer
and shouldn't be evaluated as a normal where clause condition anymore.
In the upcoming branch for WHERE clause subqueries, I want to store immutable
references to WHERE clause expressions in `Resolver`, but this is unfortunately
not possible if we still use the aforementioned mutable references.
Hence, we can temporarily make `WhereTerm::consumed` a `Cell<bool>` which allows
us to pass an immutable reference to `init_loop()`, and the `Cell` can be removed
once the virtual table constraint resolution is moved to an earlier part of the
query processing pipeline.
Currently we have some usages of LIMIT where the actual limit counter
is initialized next to the DecrJumpZero instruction, and then
`program.mark_last_insn_constant()` is used to hoist the counter
initialization to the beginning of the program.
This is very fragile, and already FROM clause subquery handling works
around this with a hack (removed in this PR), and (upcoming) WHERE clause
subqueries would also run into problems because of this, because the LIMIT
might need to be initialized once for every iteration of the subquery.
This PR removes those usages for LIMIT, and LIMIT processing is now more
intuitive:
- limit counter is now initialized at the start of the query processing
- a function init_limit() is extracted to do this for select/update/delete
1. allow calling op_null with Insn::BeginSubrtn
- BeginSubrtn is identical to Null, but named differently so that
its use in context is clearer
2. Insn::Return: add possibility to fallthrough on non-integer values as
per sqlite spec
Closes#1588
