prepared statements node-postgresql error with null result

Question

i am new in node.js and postgresql. am allready connected with postgres db and execute some test code. after am going to use prepared statements.am create a sample login script. if user exist it return username else return message "invalid username or password". if username and password is correct,it return username. but no data will present , then could not return message. my openion is that , the control will crashed after executing cliend.end() function.

this is my code

UserLogin.get = function(userName, callBack) {
    pg.connect(pgConString, function(err, client, done) {
        if (err) {
            callBack("DB connection failed. " + err, null);
            return;
        }
        var selectQuery="SELECT * from  "  + TABLE + " WHERE userName=($1)";
        var query=client.query({
                text:selectQuery,
                values:[userName],
                name:"selectQuery"});

                query.on("error", function (error) {
                 callBack("DB fetch failed. Error Message: " + err, null);});

                query.on('row', function(row) {
                callBack(null, row);});

                query.on("end", function (result) {
                client.end();
                return;
                 });
            });     
}

if row is empty, not return to callback. if row_result is not empty, its working fine.. How...???? any idea...???

try close instead of end

Shubham Batra
– Shubham Batra

2015-11-23 07:59:02 +00:00
Commented Nov 23, 2015 at 7:59 — Shubham Batra
– Shubham Batra, Commented Nov 23, 2015 at 7:59

Abdul Manaf · Accepted Answer · 2015-11-23 10:09:48Z

2

finally i got the answer. thanks for u r supports

UserLogin.get = function(userName, callBack) {
    pg.connect(pgConString, function(err, client, done) {
        if (err) {
            callBack("DB connection failed. " + err, null);
            return;
        }
        var selectQuery="SELECT * from  "  + TABLE + " WHERE userName=($1)";
       var query=client.query({
            text:selectQuery,
            values:[loginId],
            name:"selectQuery"});

            query.on("error", function (error) {
             callBack("DB fetch failed. Error Message: " + err, null);return;});

            query.on('row', function(row,result) {
            result.addRow(row);
            });

            query.on('end', function (result) {
            callBack(null,result.rows);
            client.end();
            return;
             });
        });     
}

in my old code, callback will be called everytime the query fetches 1 row from the database. am just changed the logic

answered Nov 23, 2015 at 10:09

Abdul Manaf

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3 Comments

vitaly-t Over a year ago

For simpler usage, check out pg-promise ;)

Abdul Manaf Over a year ago

we are using pg module. becasue pg-promise module could not support all postgres versions.

vitaly-t Over a year ago

That's not possible, because pg-promise uses pg module.

Jerome WAGNER · Accepted Answer · 2015-11-23 08:07:33Z

0

Your code

query.on('row', function(row) {
  callBack(null, row);
});

means that the callback will be called everytime the query fetches 1 row from the database. In the case when the query has 0 results, the callback will never be called.

answered Nov 23, 2015 at 8:07

Jerome WAGNER

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3 Comments

Abdul Manaf Over a year ago

i need to retrun all rows.

Abdul Manaf Over a year ago

if any ideas to return all rows in a single callback

Jerome WAGNER Over a year ago

you should use this form of client.query (with callback supplied) github.com/brianc/node-postgres/wiki/… - this will give you all rows in the result.

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