2cb7d441dc
Right now, we write code like
```rust
match q_once(q, inputs)?.into_tuple()? {
Some(vs) => match (vs.len(), vs.get(0), vs.get(1)) {
(2, &Some(Binding::Scalar(TypedValue::Long(a))), &Some(Binding::Scalar(TypedValue::Instant(ref b)))) => Some((a, b.clone())),
_ => panic!(),
},
None => None,
}
```
to length-check tuples coming out of the database. It can also lead
to a lot of cloning because references are the easiest thing to hand.
This commit allows to write code like
```rust
match q_once(q, inputs)?.into_tuple()? {
Some((Binding::Scalar(TypedValue::Long(a)), Binding::Scalar(TypedValue::Instant(b)))) => Some((a, b)),
Some(_) => panic!(),
None => None,
}
```
which is generally much easier to reason about.
96 lines
3 KiB
Rust
96 lines
3 KiB
Rust
// Copyright 2018 Mozilla
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
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// this file except in compliance with the License. You may obtain a copy of the
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// License at http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software distributed
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// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
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// CONDITIONS OF ANY KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations under the License.
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use std; // To refer to std::result::Result.
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use rusqlite;
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use mentat_core::{
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ValueTypeSet,
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};
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use mentat_db;
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use mentat_query::{
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PlainSymbol,
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};
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use mentat_query_pull;
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use aggregates::{
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SimpleAggregationOp,
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};
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#[macro_export]
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macro_rules! bail {
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($e:expr) => (
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return Err($e.into());
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)
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}
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pub type Result<T> = std::result::Result<T, ProjectorError>;
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#[derive(Debug, Fail)]
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pub enum ProjectorError {
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/// We're just not done yet. Message that the feature is recognized but not yet
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/// implemented.
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#[fail(display = "not yet implemented: {}", _0)]
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NotYetImplemented(String),
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#[fail(display = "no possible types for value provided to {:?}", _0)]
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CannotProjectImpossibleBinding(SimpleAggregationOp),
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#[fail(display = "cannot apply projection operation {:?} to types {:?}", _0, _1)]
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CannotApplyAggregateOperationToTypes(SimpleAggregationOp, ValueTypeSet),
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#[fail(display = "invalid projection: {}", _0)]
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InvalidProjection(String),
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#[fail(display = "cannot project unbound variable {:?}", _0)]
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UnboundVariable(PlainSymbol),
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#[fail(display = "cannot find type for variable {:?}", _0)]
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NoTypeAvailableForVariable(PlainSymbol),
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#[fail(display = "expected {}, got {}", _0, _1)]
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UnexpectedResultsType(&'static str, &'static str),
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#[fail(display = "expected tuple of length {}, got tuple of length {}", _0, _1)]
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UnexpectedResultsTupleLength(usize, usize),
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#[fail(display = "min/max expressions: {} (max 1), corresponding: {}", _0, _1)]
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AmbiguousAggregates(usize, usize),
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// It would be better to capture the underlying `rusqlite::Error`, but that type doesn't
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// implement many useful traits, including `Clone`, `Eq`, and `PartialEq`.
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#[fail(display = "SQL error: {}", _0)]
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RusqliteError(String),
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#[fail(display = "{}", _0)]
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DbError(#[cause] mentat_db::DbError),
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#[fail(display = "{}", _0)]
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PullError(#[cause] mentat_query_pull::PullError),
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}
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impl From<rusqlite::Error> for ProjectorError {
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fn from(error: rusqlite::Error) -> ProjectorError {
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ProjectorError::RusqliteError(error.to_string())
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}
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}
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impl From<mentat_db::DbError> for ProjectorError {
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fn from(error: mentat_db::DbError) -> ProjectorError {
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ProjectorError::DbError(error)
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}
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}
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impl From<mentat_query_pull::PullError> for ProjectorError {
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fn from(error: mentat_query_pull::PullError) -> ProjectorError {
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ProjectorError::PullError(error)
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}
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}
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