Struct mz_repr::RelationDesc

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pub struct RelationDesc {
    typ: RelationType,
    names: Vec<ColumnName>,
}
Expand description

A description of the shape of a relation.

It bundles a RelationType with the name of each column in the relation.

§Examples

A RelationDescs is typically constructed via its builder API:

use mz_repr::{ColumnType, RelationDesc, ScalarType};

let desc = RelationDesc::empty()
    .with_column("id", ScalarType::Int64.nullable(false))
    .with_column("price", ScalarType::Float64.nullable(true));

In more complicated cases, like when constructing a RelationDesc in response to user input, it may be more convenient to construct a relation type first, and imbue it with column names to form a RelationDesc later:

use mz_repr::RelationDesc;

let relation_type = plan_query("SELECT * FROM table");
let names = (0..relation_type.arity()).map(|i| match i {
    0 => "first",
    1 => "second",
    _ => "unknown",
});
let desc = RelationDesc::new(relation_type, names);

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§typ: RelationType§names: Vec<ColumnName>

Implementations§

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impl RelationDesc

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pub fn empty() -> Self

Constructs a new RelationDesc that represents the empty relation with no columns and no keys.

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pub fn is_empty(&self) -> bool

Check if the RelationDesc is empty.

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pub fn new<I, N>(typ: RelationType, names: I) -> Self
where I: IntoIterator<Item = N>, N: Into<ColumnName>,

Constructs a new RelationDesc from a RelationType and an iterator over column names.

§Panics

Panics if the arity of the RelationType is not equal to the number of items in names.

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pub fn from_names_and_types<I, T, N>(iter: I) -> Self
where I: IntoIterator<Item = (N, T)>, T: Into<ColumnType>, N: Into<ColumnName>,

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pub fn concat(self, other: Self) -> Self

Concatenates a RelationDesc onto the end of this RelationDesc.

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pub fn with_column<N>(self, name: N, column_type: ColumnType) -> Self
where N: Into<ColumnName>,

Appends a column with the specified name and type.

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pub fn with_key(self, indices: Vec<usize>) -> Self

Adds a new key for the relation.

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pub fn without_keys(self) -> Self

Drops all existing keys.

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pub fn with_names<I, N>(self, names: I) -> Self
where I: IntoIterator<Item = N>, N: Into<ColumnName>,

Builds a new relation description with the column names replaced with new names.

§Panics

Panics if the arity of the relation type does not match the number of items in names.

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pub fn arity(&self) -> usize

Computes the number of columns in the relation.

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pub fn typ(&self) -> &RelationType

Returns the relation type underlying this relation description.

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pub fn iter(&self) -> impl Iterator<Item = (&ColumnName, &ColumnType)>

Returns an iterator over the columns in this relation.

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pub fn iter_types(&self) -> impl Iterator<Item = &ColumnType>

Returns an iterator over the types of the columns in this relation.

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pub fn iter_names(&self) -> impl Iterator<Item = &ColumnName>

Returns an iterator over the names of the columns in this relation.

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pub fn iter_similar_names<'a>( &'a self, name: &'a ColumnName ) -> impl Iterator<Item = &'a ColumnName>

Returns an iterator over the names of the columns in this relation that are “similar” to the provided name.

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pub fn get_by_name(&self, name: &ColumnName) -> Option<(usize, &ColumnType)>

Finds a column by name.

Returns the index and type of the column named name. If no column with the specified name exists, returns None. If multiple columns have the specified name, the leftmost column is returned.

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pub fn get_name(&self, i: usize) -> &ColumnName

Gets the name of the ith column.

§Panics

Panics if i is not a valid column index.

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pub fn get_name_mut(&mut self, i: usize) -> &mut ColumnName

Mutably gets the name of the ith column.

§Panics

Panics if i is not a valid column index.

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pub fn get_unambiguous_name(&self, i: usize) -> Option<&ColumnName>

Gets the name of the ith column if that column name is unambiguous.

If at least one other column has the same name as the ith column, returns None. If the ith column has no name, returns None.

§Panics

Panics if i is not a valid column index.

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pub fn constraints_met( &self, i: usize, d: &Datum<'_> ) -> Result<(), NotNullViolation>

Verifies that d meets all of the constraints for the ith column of self.

n.b. The only constraint MZ currently supports in NOT NULL, but this structure will be simple to extend.

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impl RelationDesc

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pub fn decoder<V>(&self, part: ColumnsRef<V>) -> Result<(V, RowDecoder), String>

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pub fn encoder<'a, V>( &self, part: ColumnsMut<V> ) -> Result<(V, RowEncoder), String>

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impl Arbitrary for RelationDesc

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type Parameters = ()

The type of parameters that arbitrary_with accepts for configuration of the generated Strategy. Parameters must implement Default.
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type Strategy = BoxedStrategy<RelationDesc>

The type of Strategy used to generate values of type Self.
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fn arbitrary_with(_args: Self::Parameters) -> Self::Strategy

Generates a Strategy for producing arbitrary values of type the implementing type (Self). The strategy is passed the arguments given in args. Read more
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fn arbitrary() -> Self::Strategy

Generates a Strategy for producing arbitrary values of type the implementing type (Self). Read more
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impl Clone for RelationDesc

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fn clone(&self) -> RelationDesc

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for RelationDesc

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl<'de> Deserialize<'de> for RelationDesc

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fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>
where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer. Read more
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impl Hash for RelationDesc

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fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher. Read more
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fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher. Read more
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impl IntoIterator for RelationDesc

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type Item = (ColumnName, ColumnType)

The type of the elements being iterated over.
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type IntoIter = Zip<IntoIter<ColumnName>, IntoIter<ColumnType>>

Which kind of iterator are we turning this into?
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fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value. Read more
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impl MzReflect for RelationDesc

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fn add_to_reflected_type_info(rti: &mut ReflectedTypeInfo)

Adds names and types of the fields of the struct or enum to rti. Read more
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impl PartialEq for RelationDesc

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fn eq(&self, other: &RelationDesc) -> bool

This method tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl RustType<ProtoRelationDesc> for RelationDesc

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fn into_proto(&self) -> ProtoRelationDesc

Convert a Self into a Proto value.
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fn from_proto(proto: ProtoRelationDesc) -> Result<Self, TryFromProtoError>

Consume and convert a Proto back into a Self value. Read more
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impl Schema<Row> for RelationDesc

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type Encoder = RowEncoder

The associated PartEncoder implementor.
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type Decoder = RowDecoder

The associated PartDecoder implementor.
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fn columns(&self) -> DynStructCfg

Returns the name and types of the columns in this type.
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fn decoder(&self, part: ColumnsRef) -> Result<Self::Decoder, String>

Returns a Self::Decoder for the given columns.
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fn encoder<'a>(&self, part: ColumnsMut) -> Result<Self::Encoder, String>

Returns a Self::Encoder for the given columns.
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impl Schema2<Row> for RelationDesc

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type ArrowColumn = StructArray

The type of column we decode from, and encoder will finish into.
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type Statistics = OptionStats<StructStats>

Statistics we collect for a schema of this type.
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type Decoder = RowColumnarDecoder

Type that is able to decode values of T from Self::ArrowColumn.
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type Encoder = RowColumnarEncoder

Type that is able to encoder values of T.
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fn decoder(&self, col: Self::ArrowColumn) -> Result<Self::Decoder, Error>

Returns a type that is able to decode instances of T from the provider column.
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fn encoder(&self) -> Result<Self::Encoder, Error>

Returns a type that can encode values of T.
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fn decoder_any(&self, col: &dyn Array) -> Result<Self::Decoder, Error>

Returns a type that is able to decode instances of T from a type erased arrow::array::Array, erroring if the provided array is not Self::ArrowColumn.
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impl Serialize for RelationDesc

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fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>
where __S: Serializer,

Serialize this value into the given Serde serializer. Read more
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impl Eq for RelationDesc

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impl StructuralPartialEq for RelationDesc

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Consumes the collection and returns its first element. Read more
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Consumes the collection and returns its last element. Read more
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