I have inherited some old code. It gets a list of categories from a MySQL database table. I'm tasked with adding multilevel support to them. I've almost got it done, but for some reason it just errors out when I go to try the app in action.
The error is (you can also see it at http://detyams.ru/?cat=1):
Can't use an undefined value as an ARRAY reference at /usr/local/lib/perl5/site_perl/mach/5.18/DBI.pm line 2074, line 2231.
sub catlist
{
my $self=shift;
state $sth=$self->db->prepare(q/SELECT c.cat_id,c.cat_name,COUNT(pn.p_id) as cnt from category c
LEFT JOIN price_new pn ON (pn.cat_id=c.cat_id) GROUP BY pn.cat_id WHERE c.parent_id=?/);
$sth->execute(0);
my #catlist=$sth->fetchall_arrayref({}); # <- this call leads to the failure in the deep of DBI code.
foreach my $item (#catlist)
{
$sth->execute($item->{cat_id});
$item->{children}=$sth->fetchall_arrayref({});
}
return #catlist;
}
I've looked up some examples of using the DBI methods in there (like http://www.perlmonks.org/?node_id=284436#loh), all appear to be in accord with my code.
Oh, so, it just turned out if in case of a query syntax error (WHERE clause was placed in wrong position) fetchall_arrayref() appears to report cryptic errors instead of the underlying problem. Found out by checking server logs.
Related
I have an existing app that I am trying to upgrade from MVC5/EF6 to MVC6/EF7. We dynamically create some of our SQL tables, and as a result, have made use of the
System.Data.Entity.Database.SqlQuery
method to automatically map to entities that we use throughout our application.
This method seems to have gone away (i.e. not part of
Microsoft.Data.Entity.Infrastructure.Database ) in EF7 (or is not yet implemented). Are there plans to re-implement this method in EF7 or is there another way to accomplish this? Our project is kind of dead in the water until we figure this out.
Edited on May 20, 2015
I've been trying to make this work with FromSql, since that's what's available in Beta4, but no matter what combination of concatenated string, parameters I try, I keep getting different versions of an "Incorrect Syntax near #xxxvariable" message.
var results = Set<AssessmentResult>().FromSql("dbo.GetAssessmentResults #FieldA='Data1', #FieldB='Data2', #UserId = 2303");
var results2 = Set<AssessmentResult>().FromSql("dbo.GetAssessmentResults #FieldA= {0}", intData);
Both of these calls result in
"Incorrect syntax near '#FieldA'"
Any ideas?
We recently introduced the .FromSql() extension method on DbSet. It has the added benefit that you can continue composing LINQ on top of it.
var customers = db.Customers
.FromSql("SELECT * FROM Customer")
.Where(c => c.Name.StartsWith("A"));
I'm writing a pretty big migration and had this code (coffeescript):
db.users.find().forEach (user)->
try
#some code changing the user depending on the old state
db.users.save(user)
print "user_ok: #{user._id}"
catch error
print "user_error: #{user._id}, error was: #{error}"
Some errors occured. But they occured on already processed users:
user_ok: user_1234
#many logs
user_error: user_1234 ...
How come the loop takes already processed objects?
I ended up doing:
backup = { users: [] }
db.users.find().forEach (user)->
try
#some code changing the user depending on the old state
backup.users.push user
print "user_ok: #{user._id}"
catch error
print "user_error: #{user._id}, error was #{error}"
#loop backup and save
And it works nice now, but it seems really weird. What's the point behind all that please?
When you modify an object, it might be moved by the database. The database needs to take additional care to remember which objects have been visited already. This feature is called snapshotting, you can ask for a snapshotted query using
db.collection.find().snapshot()
However, even this doesn't make guarantees about objects that were inserted or deleted during the cursor iteration. A few more caveats are explained in the link to the documentation.
Another option is to perform an $orderby on an invariable unique index. Ideally, that index is also monotonic, so if you are using ObjectIds as primary keys then the _id field comes in pretty handy, like
db.collection.find().sort({"_id" :1});
When fields are nested, there is a problem.
foreach (Word.Field field in this.Application.ActiveDocument.Fields)
{
field.Update();
text = field.Result.Text;
}
The above code does not work.
The process starts, but winds up in an endless loop or some other process that hangs the system.
Thinking about it, I can surmise that when you update a field, it might have an effect on the fields collection - thus, the loop fails.
Does anyone have any ideas on implementing this?
P.S. I know there is a Document.UpdateFields() method to update ALL fields. However, there are reasons why I cannot use this and need to only update specific field types.
My apologies! I was going to give an example of a nested field but was trying to test some more before sending anyone (Jack) on a goose-chase.
I waited and waited and waited, and after a good 2 or 3 minutes, it finished. After the last field, it crashed with this message:
Object has been deleted.
The error was generated from the following line inside the loop:
string text = field.Code.Text;
The template is being tested on mergefields that are not being found because I am testing without database connectivity. It would be odd, but explainable, that it goes through all the fields and then, at the end of the day, the very OUTER IF field's result is "Error! Reference source not found." But I still don't get why this could happen.
Nor do I understand why looping takes 3 minutes while a call to document.Fields.Update() will do the same thing in about 1 second and NOT result in the error described above.
Again, my apologies. I never considered updating inside a loop would be vastly slower that a call to doc.fields.update().
i am writing a small perl app using the eXist database, and i am wondering is:
how can i see that my call
my $eXist = XML::eXistDB::RPC->new( destination=>$eXist_db, repository=>$bank, user=>"admin", password=>"pass" ) ;
is successful or not ?
thanx
When object initialisation fails, it will be messaged through Log::Report, so hook into that.
This only happens if the programmer to neglected to set either rpc or destination parameter. The new constructor will always return an object instance.
According to the docs:
All methods return a LIST, where the
first scalar is a return code (RC).
When that code is 0, all went well.
Otherwise, the code represent the
transport error or the exception
(refusal) as reported by the server
logic. In either case, the second
scalar in the returned list contains
the error message. For instance,
Maybe this applies also for the constructor, try:
my ($rc,$eXist) = XML::eXistDB::RPC->new( destination=>$eXist_db, repository=>$bank, user=>"admin", password=>"pass" );
now, if $rc != 0 there was an error.
I'm in a web scripting class, and honestly and unfortunately, it has come second to my networking and design and analysis classes. Because of this I find I encounter problems that may be mundane but can't find the solution to it easily.
I am writing a CGI form that is supposed to work with a MySQL DB. I can insert and delete into the DB just fine. My problem comes when querying the DB.
My code compiles fine and I don't get errors when trying to "display" the info in the DB through the browser but the data and text doesn't in fact display. The code in question is here:
print br, 'test';
my $dbh = DBI->connect("DBI:mysql:austinc4", "*******", "*******", {RaiseError => 1} );
my $usersstatement = "select * from users";
my $projstatment = "select * from projects";
# Get the handle
my $userinfo = $dbh->query($usersstatement);
my $projinfo = $dbh->query($projstatement);
# Fetch rows
while (#userrow = $userinfo->fetchrow()) {
print $userrow[0], br;
}
print 'end';
This code is in an if statement that is surrounded by the print header, start_html, form, /form, end_html. I was just trying to debug and find out what was happening and printed the statements test and end. It prints out test but doesn't print out end. It also doesn't print out the data in my DB, which happens to come before I print out end.
What I believe I am doing is:
Connecting to my DB
Forming a string the contains the command/request to the DB
Getting a handle for my query I perform on the DB
Fetching a row from my handle
Printing the first field in the row I fetched from my table
But I don't see why my data wouldn't print out as well as the end text. I looked in DB and it does in fact contain data in the DB and the table that I am trying to get data from.
This one has got me stumped, so I appreciate any help. Thanks again. =)
Solution:
I was using a that wasn't supported by the modules I was including. This leads me to another question. How can I detect errors like this? My program does in fact compile correctly and the webpage doesn't "break". Aside from me double checking that all the methods I do use are valid, do I just see something like text not being displayed and assume that an error like this occurred?
Upon reading the comments, the reason your program is broken is because query() does not execute an SQL query. Therefore you are probably calling an undefined subroutine unless this is a wrapper you have defined elsewhere.
Here is my original posting of helpful hints, which still apply:
I hope you have use CGI, use DBI, etc... and use CGI::Carp and use strict;
Look in /var/log/apache2/access.log or error.log for the bugs
Realize that the first thing a CGI script prints MUST be a valid header or the web server and browser become unhappy and often nothing else displays.
Because of #3 print the header first BEFORE you do anything, especially before you connect to the database where the script may die or print something else because otherwise the errors or other messages will be emitted before the header.
If you still don't see an error go back to #2.
CGIs that use CGI.pm can be run from a command line in a terminal session without going through the webserver. This is also a good way to debug.