@naturalcycles/datastore-lib/dist/query.util.js

Opinionated library to work with Google Datastore, implements CommonDB

const FNAME_MAP = {
    id: '__key__',
};
const OP_MAP = {
    '==': '=',
    in: 'IN',
    'not-in': 'NOT_IN',
};
export function dbQueryToDatastoreQuery(dbQuery, emptyQuery, propertyFilterClass) {
    let q = emptyQuery;
    // filter
    for (const f of dbQuery._filters) {
        // keeping "previous syntax" commented out
        // (q, f) => q.filter(f.name as string, OP_MAP[f.op] || (f.op as any), f.val),
        // Datastore doesn't allow `undefined` as filter value.
        // We don't want to throw on it, so instead we'll replace it with valid value of `null`.
        // `a > null` will return anything that's indexed
        // `a < null` should return nothing
        // `a == null` will return just that - rows with null values
        let { op, val } = f;
        if (val === undefined)
            val = null;
        q = q.filter(new propertyFilterClass(f.name, OP_MAP[op] || op, val));
    }
    // limit
    q = q.limit(dbQuery._limitValue || 0);
    // order
    for (const ord of dbQuery._orders) {
        q = q.order(ord.name, { descending: ord.descending });
    }
    // select
    if (dbQuery._selectedFieldNames) {
        const fields = dbQuery._selectedFieldNames.map(f => FNAME_MAP[f] || f);
        // Datastore requires you to specify at least one column, so if empty array is passed - it'll include __key__ at least
        if (!fields.length) {
            fields.push('__key__');
        }
        q = q.select(fields);
    }
    // cursor
    if (dbQuery._startCursor) {
        q = q.start(dbQuery._startCursor);
    }
    if (dbQuery._endCursor) {
        q = q.end(dbQuery._endCursor);
    }
    return q;
}