mentat/query-algebrizer/src/lib.rs

// 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.

extern crate mentat_core;
extern crate mentat_query;

mod types;
mod cc;

use mentat_core::{
    Schema,
};

use mentat_query::{
    FindQuery,
    FindSpec,
    SrcVar,
    WhereClause,
};

#[allow(dead_code)]
pub struct AlgebraicQuery {
    default_source: SrcVar,
    pub find_spec: FindSpec,
    has_aggregates: bool,
    pub limit: Option<u64>,
    pub cc: cc::ConjoiningClauses,
}

impl AlgebraicQuery {
    /**
     * Apply a new limit to this query, if one is provided and any existing limit is larger.
     */
    pub fn apply_limit(&mut self, limit: Option<u64>) {
        match self.limit {
            None => self.limit = limit,
            Some(existing) =>
                match limit {
                    None => (),
                    Some(new) =>
                        if new < existing {
                            self.limit = limit;
                        },
                },
        };
    }

    pub fn is_known_empty(&self) -> bool {
        self.cc.is_known_empty
    }
}

#[allow(dead_code)]
pub fn algebrize(schema: &Schema, parsed: FindQuery) -> AlgebraicQuery {
    // TODO: integrate default source into pattern processing.
    // TODO: flesh out the rest of find-into-context.
    let mut cc = cc::ConjoiningClauses::default();
    let where_clauses = parsed.where_clauses;
    for where_clause in where_clauses {
        if let WhereClause::Pattern(p) = where_clause {
            cc.apply_pattern(schema, &p);
        } else {
            unimplemented!();
        }
    }

    AlgebraicQuery {
        default_source: parsed.default_source,
        find_spec: parsed.find_spec,
        has_aggregates: false,           // TODO: we don't parse them yet.
        limit: None,
        cc: cc,
    }
}

pub use cc::{
    ColumnConstraint,
    ConjoiningClauses,
};

pub use types::{
    DatomsColumn,
    DatomsTable,
    QualifiedAlias,
    SourceAlias,
    TableAlias,
};