For example, implementing `SELECT DISTINCT` (#1517) and `UNION` (#1545)
require that we are able to create indexes without a rowid column
present. Similarly, `WITHOUT ROWID` tables require this.
I implemented this by replacing the `rowid` and `empty_record`
properties in `BtreeCursor` with
```rust
/// Whether the cursor is currently pointing to a record.
#[derive(Debug, Clone, Copy, PartialEq)]
enum CursorHasRecord {
Yes {
rowid: Option<u64>, // not all indexes and btrees have rowids, so this is optional.
},
No,
}
```
Reviewed-by: Pere Diaz Bou <pere-altea@homail.com>
Closes#1518
Previously the Operation enum consisted of:
- Operation::Scan
- Operation::Search
- Operation::Subquery
Which was always a dumb hack because what we really are doing is an
Operation::Scan on a "virtual"/"pseudo" table (overloaded names...)
derived from a subquery appearing in the FROM clause.
Hence, refactor the relevant data structures so that the Table enum now
contains a new variant:
Table::FromClauseSubquery
And the Operation enum only consists of Scan and Search.
```
SELECT * FROM (SELECT ...) sub;
-- the subquery here was previously interpreted as Operation::Subquery on a Table::Pseudo,
-- with a lot of special handling for Operation::Subquery in different code paths
-- now it's an Operation::Scan on a Table::FromClauseSubquery
```
No functional changes (intended, at least!)
Reviewed-by: Pere Diaz Bou <pere-altea@homail.com>
Closes#1529
Previously the Operation enum consisted of:
- Operation::Scan
- Operation::Search
- Operation::Subquery
Which was always a dumb hack because what we really are doing is
an Operation::Scan on a "virtual"/"pseudo" table (overloaded names...)
derived from a subquery appearing in the FROM clause.
Hence, refactor the relevant data structures so that the Table enum
now contains a new variant:
Table::FromClauseSubquery
And the Operation enum only consists of Scan and Search.
No functional changes (intended, at least!)
Primary keys that are marked as unique constraint, do not need to have
separate indexes, one is enough. In the case primary key is integer,
therefore rowid alias, we still need an index to satisfy unique
constraint.
This commit adds suport for DROP INDEX.
Bytecode produced by this commit differs from SQLITE's bytecode, main
reason we don't do autovacuum or repacking of pages like SQLITE does.
Closes#1280Closes#1444
This commit adds suport for DROP INDEX.
Bytecode produced by this commit differs from SQLITE's bytecode, main
reason we don't do autovacuum or repacking of pages like SQLITE does.
Apply affinities to a range of P2 registers starting with P1.
P4 is a string that is P2 characters long. The N-th character of the string indicates the column affinity that should be used for the N-th memory cell in the range.
This PR adds support for `DROP TABLE` and addresses issue
https://github.com/tursodatabase/limbo/issues/894
It depends on https://github.com/tursodatabase/limbo/pull/785 being
merged in because it requires the implementation of `free_page`.
EDIT: The PR above has been merged.
It adds the following:
* an implementation for the `DropTable` AST instruction via a method
called `translate_drop_table`
* a couple of new instructions - `Destroy` and `DropTable`. The former
is to modify physical b-tree pages and the latter is to modify in-memory
structures like the schema hash table.
* `btree_destroy` on `BTreeCursor` to walk the tree of pages for this
table and place it in free list.
* state machine traversal for both `btree_destroy` and
`clear_overflow_pages` to ensure performant, correct code.
* unit & tcl tests
* modifies the `Null` instruction to follow SQLite semantics and accept
a second register. It will set all registers in this range to null. This
is required for `DROP TABLE`.
The screenshots below have a comparison of the bytecodes generated via
SQLite & Limbo.
Limbo has the same instruction set except for the subroutines which
involve opening an ephemeral table, copying over the triggers from the
`sqlite_schema` table and then re-inserting them back into the
`sqlite_schema` table.
This is because `OpenEphemeral` is still a WIP and is being tracked at
https://github.com/tursodatabase/limbo/pull/768
Reviewed-by: Pere Diaz Bou <pere-altea@homail.com>
Closes#897
This PR started out as one to improve the API of extensions but I ended
up building on top of this quite a bit and it just kept going. Sorry
this one is so large but there wasn't really a good stopping point, as
it kept leaving stuff in broken states.
**VCreate**: Support for `CREATE VIRTUAL TABLE t USING vtab_module`
**VUpdate**: Support for `INSERT` and `DELETE` methods on virtual
tables.
Sqlite uses `xUpdate` function with the `VUpdate` opcode to handle all
insert/update/delete functionality in virtual tables..
have to just document that:
```
if args[0] == NULL: INSERT args[1] the values in args[2..]
if args[1] == NULL: DELETE args[0]
if args[0] != NULL && len(args) > 2: Update values=args[2..] rowid=args[0]
```
I know I asked @jussisaurio on discord about this already, but it just
sucked so bad that I added some internal translation so we could expose
a [nice API](https://github.com/tursodatabase/limbo/pull/996/files#diff-
3e8f8a660b11786745b48b528222d11671e9f19fa00a032a4eefb5412e8200d1R54) and
handle the logic ourselves while keeping with sqlite's opcodes.
I'll change it back if I have to, I just thought it was genuinely awful
to have to rely on comments to explain all that to extension authors.
The included extension is not meant to be a legitimately useful one, it
is there for testing purposes. I did something similar in #960 using a
test extension, so I figure when they are both merged, I will go back
and combine them into one since you can do many kinds at once, and that
way it will reduce the amount of crates and therefore compile time.
1. Remaining opcodes.
2. `UPDATE` (when we support the syntax)
3. `xConnect` - expose API for a DB connection to a vtab so it can
perform arbitrary queries.
Closes#996
