如何在PouchDB中使用动态字段对数据进行排序

Question

我用这个查询来索引first_name并根据它对数据进行排序，它运行得很好

try {
Users.createIndex({
index: { fields: ['first_name'] }
}).then(function (response) {
console.log(response);
}).catch(function (err) {
console.log(err);
});
const users = (await Users.find({
limit, skip: limit * (page - 1),
selector: {first_name: {$gt: null}},
sort: [ { 'first_name' : 'asc'} ]
})).docs;

但当我尝试使用变量时，它会触发错误

Error: Cannot sort on field(s) "orderBy" when using the default index

代码

orderBy = (query.params !== undefined && query.params.orderBy !== undefined) ? query.params.orderBy.sortField : 'first_name',
sortOrder = (query.params !== undefined && query.params.orderBy !== undefined) ? query.params.orderBy.sortOrder : 'asc'
console.log('orderBy: ' + orderBy) // first_name
console.log('sortOrder: ' + sortOrder) // asc
try {
Users.createIndex({
index: { fields: [orderBy] }
}).then(function (response) {
console.log(response);
}).catch(function (err) {
console.log(err);
});
const users = (await Users.find({
limit, skip: limit * (page - 1),
selector: {orderBy: {$gt: null}},
sort: [ { orderBy : sortOrder } ]
})).docs;

我如何编辑它，使其像静态变量一样与动态变量一起工作？

Answer 1

变量orderBy不会被以下代码中的值取代

selector: {orderBy: {$gt: null}},
sort: [ { orderBy : sortOrder } ]

代码从字面上计算orderBy。要为对象分配动态键，请使用对象索引器：

myObject[myVar] = myVal;

在你的代码中，应该这样做。

const query = {
selector: {},
sort: []
};
// setup selector
query.selector[prop] = {
$gt: null
};
// setup sort
let sortParam = {};
sortParam[prop] = sortDirection;
query.sort.push(sortParam);

我添加了一个pouchDB片段来说明这个概念。

let db;
// init example db instance
async function initDb() {
db = new PouchDB('test', {
adapter: 'memory'
});
await db.bulkDocs(getDocsToInstall());
}

initDb().then(async() => {
await db.createIndex({
index: {
fields: ['first_name']
}
});
await doQuery("first_name", "desc");
});
async function doQuery(prop, sortDirection) {
const query = {
selector: {},
sort: []
};
// setup selector
query.selector[prop] = {
$gt: null
};
// setup sort
let sortParam = {};
sortParam[prop] = sortDirection;
query.sort.push(sortParam);
// log the query
console.log(JSON.stringify(query, undefined, 3));
// exec the query
const users = (await db.find(query)).docs;
users.forEach(d => console.log(d[prop]));

}
// canned test documents
function getDocsToInstall() {
return [{
first_name: "Jerry"
},
{
first_name: "Bobby"
},
{
first_name: "Phil"
},
{
first_name: "Donna"
},
{
first_name: "Ron"
},
{
first_name: "Mickey"
},
{
first_name: "Bill"
},
{
first_name: "Tom"
},
{
first_name: "Keith"
},
{
first_name: "Brent"
},
{
first_name: "Vince"
},
]
}

<script src="https://cdn.jsdelivr.net/npm/pouchdb@7.1.1/dist/pouchdb.min.js"></script>
<script src="https://github.com/pouchdb/pouchdb/releases/download/7.1.1/pouchdb.memory.min.js"></script>
<script src="https://github.com/pouchdb/pouchdb/releases/download/7.1.1/pouchdb.find.min.js"></script>