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
According to [the
document](https://www.sqlite.org/pragma.html#pragma_cache_size):
```
When you change the cache size using the cache_size pragma, the change only endures for the current session. The cache size reverts to the default value when the database is closed and reopened.
```
so, we shouldn't persist cache_size to database header.
this PR also addresses two minor issues:
1. Sets the default cache_size to -2000 to align with SQLite's default
2. Uses the actual page size to calculate the cache size.
Reviewed-by: Pere Diaz Bou <pere-altea@homail.com>
Closes#1672
Implements `.database` property on Statement object.
```js
let stmt = db.prepare("SELECT 1");
stmt.database == db // will return the database object the stmt was create with
```
Reviewed-by: Diego Reis (@el-yawd)
Closes#1671
