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Implement PrimaryKey for generic (T, U, V) triplet #210

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Jan 4, 2021
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Implement PrimaryKey for generic (T, U, V) triplet #210

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43 changes: 43 additions & 0 deletions packages/storage-plus/src/keys.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ pub trait PrimaryKey<'a>: Clone {
type Pk0 = ();
type Pk1<'a> = &'a [u8];
type Pk2<'a, T = &'a [u8], U = &'a [u8]> = (T, U);
type Pk3<'a, T = &'a [u8], U = &'a [u8], V = &'a [u8]> = (T, U, V);

type PkStr<'a> = &'a str;

Expand Down Expand Up @@ -74,6 +75,33 @@ impl<'a, T: PrimaryKey<'a> + Prefixer<'a>, U: PrimaryKey<'a>> PrimaryKey<'a> for
}
}

// use generics for combining there - so we can use &[u8], PkOwned, or IntKey
impl<'a, T: PrimaryKey<'a> + Prefixer<'a>, U: PrimaryKey<'a> + Prefixer<'a>, V: PrimaryKey<'a>>
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PrimaryKey<'a> for (T, U, V)
{
type Prefix = T;
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Prefix should be (T, U)

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Good catch. Wouldn't we want to consider both prefixes as valid? I mean, (T, U) is a prefix, but wouldn't T be another valid one?

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Sure, but look how this is used.
Maybe we need to go through this all and check the usage and document it better.

I don't have the head space to go deep in here now. Best is to leave these PRs open and I will review and merge them (or comment on them) when I have the time to check all the details.

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@maurolacy maurolacy Jan 5, 2021 •
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Sure, but look how this is used.

This change will force me to change the implementation of MultiIndex, currently in review (#211).
But that's OK, as this is the right way to implement Prefix for these types. I'll do the changes, and will have a better look at the trade-offs.

Maybe we need to go through this all and check the usage and document it better.

Sure. I'll document the final format properly.

I don't have the head space to go deep in here now. Best is to leave these PRs open and I will review and merge them (or comment on them) when I have the time to check all the details.

No worries. I'll leave the MultiIndex PR open. That's the only place we're actually using / requiring this.


fn key(&self) -> Vec<&[u8]> {
let mut keys = self.0.key();
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keys.extend(&self.1.key());
keys.extend(&self.2.key());
keys
}

fn parse_key(serialized: &'a [u8]) -> Self {
let l1 = decode_length(&serialized[0..2]);
let first = &serialized[2..2 + l1];
let l2 = decode_length(&serialized[2 + l1..2 + l1 + 2]);
let second = &serialized[2 + l1 + 2..2 + l1 + 2 + l2];
let third = &serialized[2 + l1 + 2 + l2..];
(
T::parse_key(first),
U::parse_key(second),
V::parse_key(third),
)
}
}

// pub trait Prefixer<'a>: Copy {
pub trait Prefixer<'a> {
/// returns 0 or more namespaces that should length-prefixed and concatenated for range searches
Expand All @@ -98,6 +126,12 @@ impl<'a> Prefixer<'a> for Pk2<'a> {
}
}

impl<'a> Prefixer<'a> for Pk3<'a> {
fn prefix(&self) -> Vec<&[u8]> {
vec![self.0, self.1, self.2]
}
}

// Provide a string version of this to raw encode strings
impl<'a> Prefixer<'a> for PkStr<'a> {
fn prefix<'b>(&'b self) -> Vec<&'b [u8]> {
Expand Down Expand Up @@ -312,6 +346,15 @@ mod test {
assert_eq!(key, parsed);
}

#[test]
fn parse_joined_keys_pk3() {
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let key: Pk3 = (b"four", b"square", b"cinco");
let joined = key.joined_key();
assert_eq!(4 + 6 + 5 + 2 * (3 - 1), joined.len());
let parsed = Pk3::parse_key(&joined);
assert_eq!(key, parsed);
}

#[test]
fn parse_joined_keys_int() {
let key: U64Key = 12345678.into();
Expand Down