PR #2065 fixed a bug with table btree seeks concerning boundaries
of leaf pages.
The issue was that if we were e.g. looking for the first key greater than
(GT) 100, we always assumed the key would either be found on the left child
page of a given divider (e.g. divider 102), which is incorrect. #2065 has more
discussion and documentation about this, so read that one for more context.
Anyway:
We already had similar handling for index btrees, but it was baked into
the `BTreeCursor` struct's seek handling itself, whereas #2065 handled this
on the VDBE side.
This PR unifies this handling for both table and index btrees by always doing
the additional cursor advancement in the VDBE.
Unfortunately, since indexes may also need to do an additional advance when they
are looking for an exact match, this resulted in a bigger refactor than anticipated,
since there are quite a few VDBE instructions that may perform a seek, e.g.:
`IdxInsert`, `IdxDelete`, `Found`, `NotFound`, `NoConflict`.
All of these can potentially end up in a similar situation where the cursor needs
one more advance after the initial seek.
For this reason, I have extracted a common VDBE helper `fn seek_internal()` which
all the interested VDBE instructions will call to delegate their seek logic.
Current table B-Tree seek code rely on the invariant that if key `K` is
present in interior page then it also must be present in the leaf page.
This is generally not true if data was ever deleted from the table
because leaf row which key was used as a divider in the interior pages
can be deleted. Also, SQLite spec says nothing about such invariant - so
`turso-db` implementation of B-Tree should not rely on it.
This PR introduce 3 options for B-Tree `seek` result: `Found` /
`NotFound` and `TryAdvance` which is generated when leaf page have no
match for `seek_op` but DB don't know if neighbor page can have matching
data.
There is an alternative approach where we can move cursor in the `seek`
itself to the neighbor page - but I was afraid to introduce such changes
because analogue `seek` function from SQLite works exactly like current
version of the code and I think some query planner internals (for
insertion) can rely on the fact that repositioning will leave cursor at
the position of insertion:
> ** If an exact match is not found, then the cursor is always
** left pointing at a leaf page which would hold the entry if it
** were present. The cursor might point to an entry that comes
** before or after the key.
Also, this PR introduces new B-tree fuzz tests which generate table
B-tree from scratch and execute opreations over it. This can help to
reach some non trivial states and also generate huge DBs faster (that's
how this bug was discovered)
Reviewed-by: Jussi Saurio <jussi.saurio@gmail.com>
Reviewed-by: Pere Diaz Bou <pere-altea@homail.com>
Closes#2065
Let's assert **for now** that we do not read/write less bytes than
expected. This should be fixed to retrigger several reads/writes if we
couldn't read/write enough but for now let's assert.
Closes#2078
- Apart from regular states Found/NotFound seek result has TryAdvance
value which tells caller to advance the cursor in necessary direction
because the leaf page which would hold the entry if it was present
actually has no matching entry (but neighbouring page can have match)
- `OP_NewRowId` now generates new rowid semi randomly when the largest
rowid in the table is `i64::MAX`.
- Introduced new `LimboError` variant `DatabaseFull` to signify that
database might be full (SQLite behaves this way returning
`SQLITE_FULL`).
Now:
```SQL
turso> CREATE TABLE q(x INTEGER PRIMARY KEY, y);
turso> INSERT INTO q VALUES (9223372036854775807, 1);
turso> INSERT INTO q(y) VALUES (2);
turso> INSERT INTO q(y) VALUES (3);
turso> SELECT * FROM q;
┌─────────────────────┬───┐
│ x │ y │
├─────────────────────┼───┤
│ 1841427626667347484 │ 2 │
├─────────────────────┼───┤
│ 4000338366725695791 │ 3 │
├─────────────────────┼───┤
│ 9223372036854775807 │ 1 │
└─────────────────────┴───┘
```
Fixes: https://github.com/tursodatabase/turso/issues/1977
Reviewed-by: Jussi Saurio <jussi.saurio@gmail.com>
Closes#1985
Simple PR to check minor issue that `INTEGER PRIMARY KEY NOT NULL` (`NOT
NULL` is redundant here obviously) will prevent user to insert anything
to the table as rowid-alias column always set to null by `turso-db`
Reviewed-by: Jussi Saurio <jussi.saurio@gmail.com>
Closes#2063
Let's assert **for now** that we do not read/write less bytes than
expected. This should be fixed to retrigger several reads/writes if we
couldn't read/write enough but for now let's assert.
`i64::MAX`. We do this by attempting to generate random values smaller
than `i64::MAX` for 100 times and returns `DatabaseFull` error on
failure
- Introduced `DatabaseFull` error variant
Fixes: https://github.com/tursodatabase/turso/issues/1977
This is done because the compiler is refusing to inline even after
adding inline hint.
- Get refvalues from directly from registers without using
`make_record`
