ScyllaDb/Cassandra Object-Relation Mapper
Features
This library contains several crates with the following features:
- Automatic map tables to Rust
struct
s: scylla_orm_table_to_struct. See Usage. See the generated dir for the generated code. - Compile time checked queries: scylla_orm_macro (
scylla_orm_macro::query
). See Usage. - Plugin derive macro to generate business logic: scylla_orm_macro (
scylla_orm_macro::mirror
) - Automatic JSON mapping. When there is a column with type
text
, you can implement theTransformer
trait and map it to a type that implementsserde::Serialize
andserde::Deserialize
- All queries are executed as a prepared statement
- Support for Materialized Views (and mapping between the base table if the columns are the same)
Not all types are supported yet due to https://github.com/scylladb/scylla-rust-driver/issues/104
Query types
Depending on a query, a certain query type can be derived. These can be found here. These are the commonly used query types:
SelectMultiple
: Can be used as an iterator to iterate over the rowsSelectUnique
: Selects an optional unique row by full primary keySelectUniqueExpect
: Same asSelectUnique
, but fails if the row doesn't existSelectUniqueExpect
withCount
as entity type: has the specialselect_count
method for queries like "select count(*) from ..."
There are also struct
s for CRUD operations.
Usage
Automatic map tables to Rust
You can see an example on how to generate Rust struct
s in the example dir.
- In the build.rs file the
Transformer
trait is implemented and used for json mapping - In the generated dir you can see the generated
struct
s
How to implement it yourself (step-by-step guide how to mimic the example
crate):
- Add a build-dependency:
scylla_orm_table_to_struct = "0.1"
- Create a build.rs file
- Optionally implement the
Tranformer
trait (or useDefaultTransformer
) - Call
scylla_orm_table_to_struct::generate
- Build the project
An example of the structure of the generated code for table 'child' is:
- Child: a
struct
with owned values. Can be converted to ChildRef, PrimaryKey and PrimaryKeyRef - ChildRef: a
struct
where the values are all borrowed. Thisstruct
can perform insertions. Can be converted to Child, PrimaryKey and PrimaryKeyRef - PrimaryKey: a
struct
which holds the owned values of the primary key fields of Child. Can be converted to PrimaryKeyRef. - PrimaryKeyRef: a
struct
where the values are all borrowed. Thisstruct
can perform updates, deletions and selects. Can be converted to PrimaryKey - UpdatableColumn: an
enum
which holds the enum variants with owned values of columns that can be updated. Can be converted to UpdatableColumnRef. - UpdatableColumnRef: an
enum
where the values are all borrowed. This is used by PrimaryKeyRef for updates. Can be converted to UpdatableColumn.
Macros
Crate scylla_orm_macro
holds several macros that can be used to ensure compile/type checked queries. Examples on how this can be used can be found in lib.rs, method qmd
.
How to implement it yourself:
- Add dependency:
scylla_orm_macro = "0.1"
- The
query
macro returns the correct query type for the given query - The
query_base_table
macro transforms aselect
query to the materialized view table, to aselect
query of the base table mirror
andprimary_key
can be used for other derive macros