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| author | Marcos Magueta <maguetamarcos@gmail.com> | 2025-11-11 00:00:43 -0300 |
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| committer | Marcos Magueta <maguetamarcos@gmail.com> | 2025-11-11 00:00:43 -0300 |
| commit | 3063608df6ff1668f683d9d22c57fea29d728d0d (patch) | |
| tree | 36be7f6c6d901c5984c045d4ce823bd24c37e9af /src/operations.erl | |
| parent | b5dbdaa989a86477669aac0bf342029e1d2b6028 (diff) | |
| download | Sakura-3063608df6ff1668f683d9d22c57fea29d728d0d.tar.gz Sakura-3063608df6ff1668f683d9d22c57fea29d728d0d.zip | |
migrating to erlang to attach to mnesia
Diffstat (limited to '')
| -rw-r--r-- | src/operations.erl | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/src/operations.erl b/src/operations.erl new file mode 100644 index 0000000..7846caf --- /dev/null +++ b/src/operations.erl @@ -0,0 +1,15 @@ +-module(operations). +-export([select/2, project/2, cartesian_product/2]). + +%% @doc Selection - filter tuples based on a predicate +%% `Predicate` is a function that takes a tuple and returns true/false +select(Relation, Predicate) -> + sets:filter(Predicate, Relation). + +%% @doc Projection - select specific attributes from a relation +%% Note that `AttributeNames` can have duplicate keys, which are ignored +project(Relation, AttributeNames) when is_list(AttributeNames) -> + sets:map(fun (Tuple) -> maps:with(AttributeNames, Tuple) end, Relation). + +cartesian_product(Relation1, Relation2) -> + sets:from_list([maps:merge(Tuple1, Tuple2) || Tuple1 <- sets:to_list(Relation1), Tuple2 <- sets:to_list(Relation2)], [{version, 2}]). |