mentat/src/query.rs

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// Copyright 2016 Mozilla
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
// this file except in compliance with the License. You may obtain a copy of the
// License at http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software distributed
// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
// CONDITIONS OF ANY KIND, either express or implied. See the License for the
// specific language governing permissions and limitations under the License.
use std::collections::HashMap;
use rusqlite;
use rusqlite::types::ToSql;
use mentat_core::{
Schema,
TypedValue,
};
use mentat_query_algebrizer::algebrize;
pub use mentat_query::{
NamespacedKeyword,
PlainSymbol,
};
use mentat_query_parser::{
parse_find_string,
Extract partial storage abstraction; use error-chain throughout. Fixes #328. r=rnewman (#341) * Pre: Drop unneeded tx0 from search results. * Pre: Don't require a schema in some of the DB code. The idea is to separate the transaction applying code, which is schema-aware, from the concrete storage code, which is just concerned with getting bits onto disk. * Pre: Only reference Schema, not DB, in debug module. This is part of a larger separation of the volatile PartitionMap, which is modified every transaction, from the stable Schema, which is infrequently modified. * Pre: Fix indentation. * Extract part of DB to new SchemaTypeChecking trait. * Extract part of DB to new PartitionMapping trait. * Pre: Don't expect :db.part/tx partition to advance when tx fails. This fails right now, because we allocate tx IDs even when we shouldn't. * Sketch a db interface without DB. * Add ValueParseError; use error-chain in tx-parser. This can be simplified when https://github.com/Marwes/combine/issues/86 makes it to a published release, but this unblocks us for now. This converts the `combine` error type `ParseError<&'a [edn::Value]>` to a type with owned `Vec<edn::Value>` collections, re-using `edn::Value::Vector` for making them `Display`. * Pre: Accept Borrow<Schema> instead of just &Schema in debug module. This makes it easy to use Rc<Schema> or Arc<Schema> without inserting &* sigils throughout the code. * Use error-chain in query-parser. There are a few things to point out here: - the fine grained error types have been flattened into one crate-wide error type; it's pretty easy to regain the granularity as needed. - edn::ParseError is automatically lifted to mentat_query_parser::errors::Error; - we use mentat_parser_utils::ValueParser to maintain parsing error information from `combine`. * Patch up top-level. * Review comment: Only `borrow()` once.
2017-02-24 23:32:41 +00:00
};
use mentat_sql::{
SQLQuery,
};
use mentat_query_translator::{
query_to_select,
};
pub use mentat_query_projector::{
QueryResults,
};
use errors::Result;
pub type QueryExecutionResult = Result<QueryResults>;
/// Take an EDN query string, a reference to a open SQLite connection, a Mentat DB, and an optional
/// collection of input bindings (which should be keyed by `"?varname"`), and execute the query
/// immediately, blocking the current thread.
/// Returns a structure that corresponds to the kind of input query, populated with `TypedValue`
/// instances.
/// The caller is responsible for ensuring that the SQLite connection is in a transaction if
/// isolation is required.
#[allow(unused_variables)]
pub fn q_once<'sqlite, 'schema, 'query, T, U>
(sqlite: &'sqlite rusqlite::Connection,
schema: &'schema Schema,
query: &'query str,
inputs: T,
limit: U) -> QueryExecutionResult
where T: Into<Option<HashMap<String, TypedValue>>>,
U: Into<Option<u64>>
{
// TODO: validate inputs.
let parsed = parse_find_string(query)?;
let mut algebrized = algebrize(schema, parsed)?;
if algebrized.is_known_empty() {
// We don't need to do any SQL work at all.
return Ok(QueryResults::empty(&algebrized.find_spec));
}
algebrized.apply_limit(limit.into());
let select = query_to_select(algebrized);
let SQLQuery { sql, args } = select.query.to_sql_query()?;
let mut statement = sqlite.prepare(sql.as_str())?;
let rows = if args.is_empty() {
statement.query(&[])?
} else {
let refs: Vec<(&str, &ToSql)> =
args.iter()
.map(|&(ref k, ref v)| (k.as_str(), v.as_ref() as &ToSql))
.collect();
statement.query_named(refs.as_slice())?
};
select.projector
.project(rows)
.map_err(|e| e.into())
}