Question

我在writing matched lines with node js in CSV上问了一个问题并得到了满意的答复。现在我正在通过节点进入我的新手冒险的下一级别。我想设置模拟rdb的递归查询，有点（这是我希望节点有类似Perl DBD::CSV的东西。

更新：我觉得我对节点世界中的事物的异步性有所了解，需要了解它是如何工作的。这是我想要做的 -

查询所有匹配食物的食物文件。
对于上面＃1中的每种匹配食物，找到营养素文件中的所有营养素。
对于上述＃2中的每种匹配营养素，在营养素定义文件中找到它们的定义。
将整个数据结构作为嵌套的JSON返回并将其交给可视化工具（命令行或html，当我最终将整个鼠标的包裹放入RESTful框架，例如expressjs时。

是的，如果我将所有内容都放入SQLite，我可以更加轻松地完成这一切，但我是一个痛苦的傻瓜。这将是理解节点如何处理流的好方法。

到目前为止，这是我的代码

#!/usr/bin/env node

var Argv = require("optimist").argv,
    Csv = require("csv"),
    Fs = require("fs");

var db = {
    "dir": "/../data/sr26",
    "foods": {
        "file": "FOOD_DES.txt",
        "columns": [
            "NDB_No", "FdGrp_Cd", "Long_Desc", "Shrt_Desc", "ComName",
            "ManufacName", "Survery", "Ref_desc", "Refuse", "SciName",
            "N_Factor", "Pro_Factor", "Fat_Factor", "CHO_Factor"
        ],
        "PK": "NDB_No",
        "search": "Long_Desc"
    },
    "nutrients": {
        "file": "NUT_DATA.txt",
        "columns": [
            "NDB_No", "Nutr_No", "Nutr_Val", "Num_Data_Pts", "Std_Error",
            "Src_Cd", "Deriv_Cd", "Ref_NDB_No", "Add_Nutr_Mark", 
            "Num_Studies", "Min", "Max", "DF", "Low_EB", "Up_EB", 
            "Stat_cmt", "AddMod_Date", "CC"
        ],
        "PK": "NDB_No",
        "search": "NDB_No"
    },
    "nutrient definitions": {
        "file": "NUTR_DEF.txt",
        "columns": [
            "Nutr_No", "Units", "Tagname", "NutrDesc", "Num_Dec", "SR_Order"
        ],
        "PK": "Nutr_No",
        "search": null
    },
    "query": function(table, value, done) {
        var re = new RegExp(value);

        Csv()
        .from.stream(
            Fs.createReadStream(__dirname + db.dir + "/" + db[table].file),
            {
                "delimiter": "^",
                "quote": "~",
                "columns": db[table].columns
            }
        )
        .transform(function(row, index, callback) {
            if (row[ db[table].search ].search(re) != -1) {
                process.nextTick(function() {
                     callback(null, row)
                });
            }
            else {
                callback(null, null);
            }
        })
        .on("record", function(row, index) {
            console.log("done is " + done);
            if (done == true) {
                console.log(JSON.stringify(row));
            }
            else {
                console.log("found " + table + " '" + value + "' with PK: " + row[ db[table].PK ]);
                console.log("\tnow querying 'nutrients' for " + row[ db[table].PK ] + "\n");
                db.query("nutrients", row[ db[table].PK ], true);
            }
        });
    }
};

if (Argv.table) {
    console.time("searching");
    db.query(Argv.table, Argv.value, false);
    console.timeEnd("searching");
}

$ bin/app.js --table foods --value "Dandelion green"
searching: 4ms
done is false
found foods 'Dandelion green' with PK: 11207
    now querying 'nutrients' for 11207

done is false
found foods 'Dandelion green' with PK: 11208
    now querying 'nutrients' for 11208

done is false
found foods 'Dandelion green' with PK: 11782
    now querying 'nutrients' for 11782

正如你所看到的，运行上面的吐痰，嗯，真的没什么。我期待营养价值在第二个循环中打印出来“（完成是真的）”，但“完成”永远不会设置为 true 。在我更好地学习节点的过程中，我寻求上述的具体和一般指导。

通过节点js递归查询多个CSV

0 个答案: