tribedb/lib/select.js

Unlimited expansion MySQL cluster storage system

/**
 *
 * select
 * 
 */


const pool = require('./pool.js');
const config = require('./config.js');



/**
 * 数据适配处理
 */
function dataHandle(table, data)
{
    let is_single = ! Array.isArray(data);
    if(is_single){
        dataHandleSingle(table, data);
    }else{
        for(let i in data){
            dataHandleSingle(table, data[i]);
        }
    }
}
function dataHandleSingle(table, data)
{
    let handles = config.dataAdapter[table];
    if( ! handles ){
        return;
    }
    // 开始处理
    for(let i in handles){
        handles[i](data);
    }
}







/**
 * 查询数据
 */
exports.select = function(table, field, where, single)
{
    return new Promise(function (resolve, reject) {
        select(table, (field||'*'), where, single, function(err, rows){
            err && reject(err);
            resolve(rows);
        });
    });
};



/**
 * 异步查询数据
 */
function select(table, field, where, single, callback)
{
    pool.conn(table, {read:1}, function(err, conn){
        if(err) callback(err);
        if(where) where = ' WHERE '+where;
        if(single) where += ' LIMIT 1';
        let sql = "SELECT "+field+" FROM `"+table+"` "+where;
        // console.log(sql);
        conn.query(sql, function(err, rows){
            conn.release(); // 必须释放回连接池！
            if(err) return callback(err);
            let resdata = single ? rows[0] : rows;
            dataHandle(table, resdata); // 数据适配处理
            callback(null, resdata); // 返回
        });
    });
}



/**
 * 查询 多个表 数据 并自动组装
 */
exports.select_merge = function(conditions)
{
return new Promise(function (resolve, reject) {

    let step = 0 
      , length = 0
      , mgkey = 'id' // 组装键
      , single = false
      , datas = []
      , single_res = {} // 返回
      ;
    for(let table in conditions){
        let one = conditions[table];
        if(!length){ // 配置
            single = one.single;
            mgkey = one.key || mgkey;
        }
        // 请求数据
        query(one)
        length++;
    }

    // 到达
    function query(one)
    {
        select(one.table, (one.field||'*'), one.where, single, function(err, rows){
            step++;
            if(err) return reject(err);
            datas.push(rows);
            if(single) single_res = Object.assign(single_res, rows);
            if(step==length) merge(); // 合并
        });
    }

    // 合并
    function merge()
    {
        if(single){
            return resolve(single_res);
        }
        // 合并
        let res = []
          , leg = datas.length
          ;
        for(let i in datas[0]){
            let one = datas[0][i];
            for(let j=1; j<leg; j++){
                one = Object.assign(one, array_select(datas[j], mgkey, one[mgkey]) );
            }
            res.push(one);
        }
        return resolve(res);
    }

});
}



/**
 * 查询附带
 */
exports.select_attach = function(data, table, field, opt)
{
return new Promise(async (resolve, reject)=>{

    opt = opt || {};
    field = Array.isArray(field) ? field : field.split(',');

    // 参数
    let data_key = opt['key'] || table+'_id';
    let auto_id = opt['id'] || 'id';
    let shield = opt['shield'] || '';
    let delkey = opt['delkey'];

    // 开关
    let single = ! Array.isArray(data);
    if(single){
        data = [data];
    }
    let hasid = field.indexOf(auto_id) > -1;
    if(!hasid && field.indexOf('*')==-1){
        field.unshift('`'+auto_id+'`');
    }

    // 取出id列表
    let ids = array_unique(array_listem(data, data_key));
    if( ids.length ){
        // 批量查询数据
        let infos = await exports.select(table, field.join(','), auto_id+' IN('+ids.join(',')+')');
        dataHandle(table, infos); // 数据适配处理
        // 拼装数据
        for(let i in data){
            let info = array_select(infos, auto_id, data[i][data_key]);
            if( !info ) continue;
            if( !hasid ){
                // delete info[auto_id];
            }
            if(shield){
                data[i][shield] = Object.assign({}, info);
            }else{
                data[i] = Object.assign({}, data[i], info);
            }
            if(delkey){ // 删除 key
                delete data[i][ data_key ];
            }
        }
    }
    // 输出
    resolve(single ? data[0] : data);

});
}




/**
 * 解析 条件生成 SQL
 */
function array_select(arr, k, v)
{
    for(let i in arr){
        let one = arr[i];
        if(one[k]==v){
            return one;
        }
    }

    return null;
}



/**
 * 取得数组中元素的某个属性 单独返回数组元素
 */
function array_listem (ary, key) {
    var reary = []
        , leg = ary.length;
    for(var i=0; i<leg; i++){
        var d = ary[i][key];
        d?reary.push(d):0;
    }
    return reary;
};


/**
 * 去重
 */
function array_unique(ary){
    var s=new Set();
    ary.map((item,index)=>{
        s.add(item)
    })
    var temp=[];
    for(var i of s){
        temp.push(i)
    }
    return temp;
}


/**
 * 解析 条件生成 SQL
 */
function parseCondition(cond)
{


}