Bind variables in CQL have two formats: positional (`?`) where a
variable is referred to by its relative position in the statement,
and named (`:var`), where the user is expected to supply a
name->value mapping.
In 19a6e69001 we identified the case where a named bind variable
appears twice in a query, and collapsed it to a single entry in the
statement metadata. Without this, a driver using the named variable
syntax cannot disambiguate which variable is referred to.
However, it turns out that users can use the positional call form
even with the named variable syntax, by using the positional
API of the driver. To support this use case, we add a configuration
variable to disable the same-variable detection.
Because the detection has to happen when the entire statement is
visible, we have to supply the configuration to the parser. We
call it the `dialect` and pass it from all callers. The alternative
would be to add a pre-prepare call similar to fill_prepare_context that
rewrites all expressions in a statement to deduplicate variables.
A unit test is added.
Fixes#15559
This patch adds a reproducer for a minor compatibility between Scylla's
and Cassandra's handling of a prepared statement when a bind marker with
the same name is used more than once, e.g.,
```
SELECT * FROM tbl WHERE p=:x AND c=:x
```
It turns out that Scylla tells the driver that there is only one bind
marker, :x, whereas Cassandra tells the driver that there are two bind
markers, both named :x. This makes no different if the user passes
a map `{'x': 3}`, but if the user passes a tuple, Scylla accepts only
`(3,)` (assigning both bind markers the same value) and Cassandra
accepts only `(3,3)`.
The test added in this patch demonstrates this incompatibility.
It fails on Scylla, passes on Cassandra, and is marked "xfail".
Refs #15559
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Closesscylladb/scylladb#15564
Issue #15374 has been fixed, so these tests can be enabled.
Duplicate bind variable names are now handled correctly.
Signed-off-by: Jan Ciolek <jan.ciolek@scylladb.com>
Add some tests that test whether `pk indexes` are generated correctly.
When a driver asks to prepare a statement, Scylla's response includes
the metadata for this prepared statement.
In this metadata there's `pk indexes`, which tells the driver which
bind variable values it should use to calculate the partition token.
For a query like:
SELECT * FROM t WHERE p2 = ? AND p1 = ? AND p3 = ?
The correct pk_indexes would be [1, 0, 2], which means
"To calculate the token calculate Hash(bind_vars[1] | bind_vars[0] | bind_vars[2])".
More information is available in the specification:
1959502d8b/doc/native_protocol_v4.spec (L699-L707)
Two tests are marked as xfail because of #15374 - Scylla doesn't correctly handle using the same
named variable in multiple places. This will be fixed soon.
I couldn't find a good place for these tests, so I created a new file - test_prepare.py.
Signed-off-by: Jan Ciolek <jan.ciolek@scylladb.com>
