These tests verify interactions between the database engine and TVFs.
They happen to use generate_series, but they are not intended to test
the behavior of any specific extension. Tests that verify generate_series
specific behavior remain in extensions.py.
There is a distinction between tests that verify extension-specific
behavior and tests that verify interactions between the database engine
and extensions. Previously, both types of tests were kept in extensions.py.
With this new framework, we can extract the latter type of tests from
extensions.py into TCL. This cleans up extensions.py and provides
compatibility testing with SQLite at no extra cost.
To demonstrate the framework’s usage, tests verifying the handling of
virtual tables were extracted to TCL.
In the future, we may consider moving extension-specific tests to TCL as
well, especially those that have counterparts in SQLite or sqlean.
This change extends table-valued function support by allowing arguments
to be column references, not only literals.
Virtual tables can now reject a plan by returning an error from
best_index (e.g., when a TVF argument references a table that appears
later in the join order). The planner using this information excludes
invalid plans during join order search.
This change connects virtual tables with the query optimizer.
The optimizer now considers virtual tables during join order search
and invokes their best_index callbacks to determine feasible access
paths.
Currently, this is not a visible change, since none of the existing
extensions return information indicating that a plan is invalid.
The `filter` methods for extensions affected by this fix expect arguments
to be passed in a specific order. For example, `generate_series` assumes
that if the `start` argument exists, it is always passed to `filter`
first. If `start` does not exist, then `stop` is passed first — but
`stop` must never come before `start`.
Previously, this was not guaranteed: `best_index` relied on constraints
being passed in the order matching `filter`'s expectations.
- Fix not being able to create table while importing
* The behavior now aligns with SQLite so that if the table already
exists, all the rows are treated as data. If the table doesn't exist,
the first row is treated as the header from which column names for the
new table are populated.
- Insert in batches instead of one at a time
With this change, the following two queries are considered equivalent:
```sql
SELECT value FROM generate_series(5, 50);
SELECT value FROM generate_series WHERE start = 5 AND stop = 50;
```
Arguments passed in parentheses to the virtual table name are now
matched to hidden columns.
Column references are still not supported as table-valued function
arguments. The only difference is that previously, a query like:
```sql
SELECT one.value, series.value
FROM (SELECT 1 AS value) one, generate_series(one.value, 3) series;
```
would cause a panic. Now, it returns a proper error message instead.
Adding support for column references is more nuanced for two main
reasons:
- We need to ensure that in joins where a TVF depends on other tables,
those other tables are processed first. For example, in:
```sql
SELECT one.value, series.value
FROM generate_series(one.value, 3) series, (SELECT 1 AS value) one;
```
the one table must be processed by the top-level loop, and series must
be nested.
- For outer joins involving TVFs, the arguments must be treated as ON
predicates, not WHERE predicates.
We need to enumerate first and filter afterward — not the other way
around — because we later use the indexes produced by `enumerate` to
access the original `predicates` slice.
Previously, the test queries added in this commit would fail with:
thread 'main' panicked at core/schema.rs:129:34:
not implemented
stack backtrace:
0: rust_begin_unwind
at /rustc/90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf/library/std/src/panicking.rs:665:5
1: core::panicking::panic_fmt
at /rustc/90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf/library/core/src/panicking.rs:74:14
2: core::panicking::panic
at /rustc/90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf/library/core/src/panicking.rs:148:5
3: limbo_core::schema::Table::get_root_page
at ./core/schema.rs:129:34
4: limbo_core::translate::main_loop::init_loop
at ./core/translate/main_loop.rs:260:44
5: limbo_core::translate::emitter::emit_query
at ./core/translate/emitter.rs:568:5
6: limbo_core::translate::emitter::emit_program_for_select
at ./core/translate/emitter.rs:496:5
7: limbo_core::translate::emitter::emit_program
at ./core/translate/emitter.rs:187:31
8: limbo_core::translate::select::translate_select
at ./core/translate/select.rs:82:5
9: limbo_core::translate::translate_inner
at ./core/translate/mod.rs:241:13
10: limbo_core::translate::translate
at ./core/translate/mod.rs:95:17
11: limbo_core::Connection::run_cmd
at ./core/lib.rs:416:31
12: <limbo_core::QueryRunner as core::iter::traits::iterator::Iterator>::next
at ./core/lib.rs:916:22
13: limbo::app::Limbo::run_query
at ./cli/app.rs:442:27
14: limbo::app::Limbo::handle_input_line
at ./cli/app.rs:544:13
15: limbo::main
at ./cli/main.rs:51:31
16: core::ops::function::FnOnce::call_once
We're now mixing different error messages, which makes compatibility
testing pretty hard. Unify on a single, SQLite compatible error message
"no such table".
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
