I am currently evaluating whether ArangoDB can be a future alternative for us. As a part of this evaluation I am porting code that talks to our current NoSQL db into code that speaks ArangoDB. While it has been a fairly smooth ride so far, I am having surprisingly difficult to wrap my head around on how to update sub documents. Assuming we have something like this:
{
"_key": "12345",
"subdoc": {
"0": {
"num_sold": 6,
"other_attribute": "important"
},
"1": {
"num_sold": 4,
"other_attribute": "important"
}
}
}
What I would like to accomplish now it to atomically increase num_sold.
A very first naive approach was of course to try something similar to:
FOR d in ##collection
FILTER d._key == "12345"
UPDATE d WITH { subdoc.0.num_sold : subdoc.0.num_sold + 1 } IN ##collection
RETURN d
(Spoiler alert for the copy-pasters out there: move on. This snippet will just make your life miserable.)
This obviously didn't work and most likely for more than one reason. Arango does not seem to like me referencing the attribute using dot notation, the attribute starting with a number ("0") might also be an issue etc. While having found an example here it seemed both a bit complicated and convoluted for what I am trying to do. There is also another discussion here that is close to what I would like to do. However, the proposed solution in that discussion uses the keyword OLD that creates an error in my case as well as the code replacing all keys in "0".
1) What is the best way to atomically increase num_sold?
2) When is an operation atomic? (Trying to stay away from transactions as long as possible)
3) When can the dot notation be used and when can it not be used?
4) Can I bind parameters to an attribute? For instance letting some #attribute be subdoc.0.num_sold?
Thanks!
ArangoDB can't parse the query if you use numbers in the dot notation.
However there is an easy way - simply use brackets instead of the dot notation as you did.
Example - not working:
db._query(`
LET testdoc = {subdoc: {"0": "abc"}}
RETURN testdoc.subdoc.0`)
ArangoError 1501: syntax error, unexpected integer number,
expecting identifier or bind parameter near '0' at
position 1:60 (while parsing)
Example - fixed:
db._query(`
LET testdoc = {subdoc: {"0": "abc"}}
RETURN testdoc.subdoc.[0]`)
[
"abc"
]
Using bind variables - not working:
db._query(`
LET testdoc = {subdoc: {"0": "abc"}}
RETURN testdoc.subdoc.#bv`, {bv: 0})
ArangoError 1501: syntax error, unexpected integer number,
expecting identifier or bind parameter near '0' at
position 1:60 (while parsing)
Using bind variables - fixed:
db._query(`
LET testdoc = {subdoc: {"0": "abc"}}
RETURN testdoc.subdoc.[#bv]`, {bv:0})
[
"abc"
]
Related
How do we write conditions in arango, that includes for loops. I can elaborate the requirement below.
My requirement is if a particular attribute(array type) exists in the arango collection, i would read data from the collection(that requires a loop) or else, might do the following :
return null
return empty string ""
do nothing.
Is this possible to achieve in arango?
The helping methods could be -->
-- has(collectionname, attributename)
-- The ternary operator ?:
let attribute1 = has(doc,"attribute1") ?(
for name in doc.attribute1.names
filter name.language == "xyz"
return name.name
) : ""
But this dosent work. Seems like arango compiler first attempts to compile the for loop, finds nulls and reports error as below. Instead, it should have compiled "has" function first for the ternary operator being used.
collection or array expected as operand to FOR loop; you provided a value of type 'null' (while executing)
If there is a better way of doing it, would appreciate the advice!!
Thanks in advance!
Nilotpal
Fakhrany here from ArangoDB.
Regarding your question, this is a known limitation.
From https://www.arangodb.com/docs/3.8/aql/fundamentals-limitations.html:
The following other limitations are known for AQL queries:
Subqueries that are used inside expressions are pulled out of these
expressions and executed beforehand. That means that subqueries do not
participate in lazy evaluation of operands, for example in the ternary
operator. Also see evaluation of subqueries.
Also noted here for the ternary operator:
https://www.arangodb.com/docs/3.8/aql/operators.html#ternary-operator.
An answer to the question what to do may be to use a FILTER before enumerating over the attributes:
FOR doc IN collection
/* the following filter will only let those documents passed in which "attribute1.names" is an array */
FILTER IS_ARRAY(doc.attribute1.names)
FOR name IN doc.attribute1.names
FILTER name.language == "xyz"
RETURN name.name
Other solutions are also possible. Depends a bit on the use case.
I am working in a groovy/grails set up and am having some trouble trying to execute a switch statement on a String value.
Basically, I am looping through the attribute names in a webservice response to see if they match pre-defined mappings that are configured on a per user basis. If they have established a mapping on that field, I pull the value out of the response and use it elsewhere.
The code looks something like this:
switch(attributeName)
{
case {attributeName} :
log.info("Currently switching on value... ${attributeName}")
case user.getFirstNameMapping():
model.user.userInfo.firstName = attributeValue
break
case user.getLastNameMapping():
model.user.userInfo.lastName = attributeValue
break
case user.getAuthenticationKeyMapping():
model.authenticationValue = attributeValue
break
case user.getEmailMapping():
model.email = attributeValue.toLowerCase()
break
}
The value being switched on (attributeName) is of type String, and the getter methods for the user instance also return type String.
Based on my research and understanding of the Groovy language, switching on an Object such as a String should end up using String.equals() to make the comparison. The result, however, is that it is matching on the user.getFirstNameMapping() case every time, and repeatedly overwriting the value in the model; therefore, the last value that comes back in the response is what ends up saved, and none of the other values are saved.
What's interesting is that if I use an if/else structure and do something like this:
if(attributeName.equals(user.getFirstNameMapping())
{
...
}
It works fine every time. I've verified through logging that it's not something silly like extra whitespace or a capitalization issue. I've also tried changing things around to run the switch by default and explicitly compare the attributeName in the case like this:
switch(true)
{
case {attributeName} :
log.info("Currently switching on value... ${attributeName}")
case {user.getFirstNameMapping().equals(attributeName)}:
model.user.userInfo.firstName = attributeValue
break
case {user.getLastNameMapping().equals(attributeName)}:
model.user.userInfo.lastName = attributeValue
break
case {user.getAuthenticationKeyMapping().equals(attributeName)}:
model.authenticationValue = attributeValue
break
case {user.getEmailMapping().equals(attributeName)}:
model.email = attributeValue.toLowerCase()
break
}
And it still fails to meet my expectations in the exact same way. So, I'm wondering why this is the behavior when the switch statement should simply be using .equals() to compare the strings, and when I explicitly compare them in an if/else using .equals(), it works as expected.
The issue is in your switch case.
Have a look here :-
case {attributeName} :
log.info("Currently switching on value... ${attributeName}")
case user.getFirstNameMapping():
model.user.userInfo.firstName = attributeValue
break
As you can see your these two cases will run every time because the switch condition is :-
switch(attributeName)
So the first one will get match and will run until it encounters break; which is at after case 2 i.e. case user.getFirstNameMapping(): so i would suggest you to print the value of {attributeName} before the swtich starts.
Hope that will help you.
Thanks
I don't know exactly what's your issue, but the case statement works just fine, even with methods. See my example
String something = "Foo"
class User {
String firstName
String lastName
}
User u = new User(firstName: 'Something', lastName:'Foo')
switch(something) {
case u.getFirstName():
println "firstName: ${u.firstName}"
break;
case u.getLastName():
println "lastName: ${u.lastName}"
break;
default:
println "nothing..."
}
This code will print lastName as expected.
I have no idea how to check for this. My method(if condition in method) should only work (execute) if the first argument passed in is a string. I know how to check other types, but I can't seem to find anything for checking for a string.
For a hash I would do something like;
if(ref eq 'HASH') {...}
If someone could provide a simple example I'm sure I would be able to apply it to what I'm doing. I will put up the code for the method and an explanation for the whole operational details of the method if needed.
Added Information
This is a method for handling different types of errors in the software, here are the 3 possible input formats:
$class->new("error string message")
$class->new("error string message", code => "UNABLE_TO_PING_SWITCH_ERROR")
$class->new("error string message", code => "UNABLE_TO_PING_SWITCH_ERROR", switch_ip => $ip3, timeout => $timeout)
There will always be an error message string first.
With the 1st case there is also a hashref to an error hash structure that is located in a library,
this method new will go into a template processing if the word "code" exists as an arg. where the longer detailed error message is constructed. (I already have the logic for this).
But I have to add logic so that the error message string is added to the hash, so the output is one hash, and not strings.
The second case is very similar to the first, where there are parameters eg. switch_ip , which are inserted into the string using a similar template processing logic, (already have this too).
So I think the first and second cases can be handled in the same way, but I'm not sure, so separated them in this question.
The last case is just can error message string by itself, which at the minute I just insert it into a one key message hash { message => "error string}.
So after all that how should I be checking or dividing up these error cases, At the minute my idea for the ones with code , is to dump the arguments into a hash and just use something like:
if(exists($param{code}) { doTemplateProcess()...}
I need to ensure that there is a string passed in first though. Which was my original question. Does any of my context information help? I hope I didn't go off the topic of my question, if so I'll open this a new question. Thanks.
Error hash - located in Type.pm
use constant ERROR_CODE => {
UNABLE_TO_PING_SWITCH_ERROR => {
category => 'Connection Error:',
template => 'Could not ping switch %s in %s minutes',
tt => {template => 'disabled'},
fatal => 1,
wiki_page => www.error-solution.com/,
},
}
From comments:
These will be called in the software's code like so
ASC::Builder::Error->new(
"Phase x this occured because y was happening:",
code => UNABLE_TO_PING_SWITCH_ERROR,
switch_ip => $ip3,
timeout => 30,
);
Putting the wisdom of your particular problem aside and channeling Jeff Foxworthy:
If you have a scalar and it's not a reference, you might have a string.
If your non-reference scalar doesn't look like a number, it might be a string.
If your non-reference scalar looks like a number, it can still be a string.
If your non-reference scalar has a different string and number value, it might be a dualvar.
You know that your argument list is just that: a list. A list is a collection of scalar values. A scalar can be a reference or not a reference. I think you're looking for the not a reference case:
die "You can't do that" if ref $first_argument;
Past that, you'd have to do fancier things to determine if it's the sort of value that you want. This might also mean that you reject objects that pretend to be strings through overloading and whatnot.
Perhaps you can make the first argument part of the key-value pairs that you pass. You can then access that key to extract the value and delete it before you use the remaining pairs.
You may easily check only whether the error string is a simple scalar value or a reference. You would do that with ref, but you must consider what you want to do if the first parameter isn't a string
You should write your constructor in the ASC::Builder::Error package along these lines
sub new {
my $class = shift;
my ($error, %options) = #_;
die if ref $error;
bless { string => $error }, $class;
}
This example simply dies, and so kills the program, if it is called with anything other than a simple string or number as the first parameter
You may call it as
ASC::Builder::Error->new('error')
or
ASC::Builder::Error->new(42)
and all will be well. If you try
ASC::Builder::Error->new('message', 'code')
then you will see a warning
Odd number of elements in hash assignment
And you may make that warning fatal
If there is anything more then you should explain
Supporting all of the following is simple:
$class->new("s")
$class->new("s", code => "s")
$class->new("s", code => "s", switch_ip => "s", timeout => "s")
All you need is the following:
sub new {
my ($class, $msg, %opts) = #_;
...
}
You can checks such as the following to examine what the called provided:
if (exists($opts{code}))
if (defined($opts{code}))
if ($opts{code})
Despite saying that the string will always be provided, you now ask how to check if was provided. As such, you are probably trying to perform validation rather than polymorphism. You shouldn't waste your time doing this.
Let's look at the hash reference example you gave. ref($arg) eq 'HASH' is wrong. That returns false for some hash references, and it returns false for some things that act like a reference to a hash. The following is a more proper check:
eval { %$arg; 1 }
The equivalent for strings would be the following:
eval { "$arg"; 1 }
Unfortunately, it will always return true! Every value can act as a string. That means the best thing you can do is simply to check if any argument is provided.
use Carp qw( croak );
croak("usage") if !#_;
It's rare for Perl subs to perform argument validation. Not only is it tricky, it's also expensive. It also provides very little benefits. Bad or missing arguments usually results in exceptions or warnings shortly after.
You might see suggestions to use croak("usage") if ref($arg); (or worse, die if ref($arg);), but keep in mind that those will cause the rejection of perfectly fine objects that overload stringification (which is somewhat common), and they will fail to detect the problem with ASC::Builder::Error->new(code => ...) because code produces a string. Again, performing type-based argument validation is an expensive and buggy practice in Perl.
Could somebody tell me what I'm doing wrong in this query to get a calculated column?
IIf(Left([VIN Number],2)="1F" OR "2F" OR "3F" OR "1L” OR “2L” OR “NM”,”Food”,"Comp")
It's giving me error saying "you may have entered an operand without an operator"
You can't have a compound condition like ...
Something = "a" OR "b"
You would have to repeat the Something = after OR ...
Something = "a" OR Something = "b"
For your query's IIf() expression, an In() list containing the match values would be more concise ...
IIf(Left([VIN Number],2) IN ("1F", "2F", "3F", "1L", "2L", "NM"), "Food", "Comp")
Beware your code sample includes typesetting quotes (“ and ”). Make sure you use plain quotes (") in your real code.
The OR operator doesn't work how you expect it to. It requires statements that resolve to TRUE or FALSE on either side of it, so you can't check if something is equal to one of many things like this.
You either need to do:
Iif(Left([VIN Number],2)="1F" OR Left([VIN Number],2)="2F" OR Left([VIN Number],2)="3F"...., "Food", "Comp")
or you need to do:
Iif(Left([VIN Number],2) In("1F","2F", "3F"....), "Food", "Comp")
I have an elasticsearch index that contains various member documents. Each member document contains a membership object, along with various fields associated with / describing individual membership. For example:
{membership:{'join_date':2015-01-01,'status':'A'}}
Membership status can be 'A' (active) or 'I' (inactive); both Unicode string values. I'm interested in providing a slight boost the score of documents that contain active membership status.
In my groovy script, along with other custom boosters on various numeric fields, I have added the following:
String status = doc['membership.status'].value;
float status_boost = 0.0;
if (status=='A') {status_boost = 2.0} else {status_boost=0.0};
return _score + status_boost
For some reason associated with how strings operate via groovy, the check (status=='A') does not work. I've attempted (status.toString()=='A'), (status.toString()=="A"), (status.equals('A')), plus a number of other variations.
How should I go about troubleshooting this (in a productive, efficient manner)? I don't have a stand-alone installation of groovy, but when I pull the response data in python the status is very much so either a Unicode 'A' or 'I' with no additional spacing or characters.
#VineetMohan is most likely right about the value being 'a' rather than 'A'.
You can check how the values are indexed by spitting them back out as script fields:
$ curl -XGET localhost:9200/test/_search -d '
{
"script_fields": {
"status": {
"script": "doc[\"membership.status\"].values"
}
}
}
'
From there, it should be an indication of what you're actually working with. More than likely based on the name and your usage, you will want to reindex (recreate) your data so that membership.status is mapped as a not_analyzed string. If done, then you won't need to worry about lowercasing of anything.
In the mean time, you can probably get by with:
return _score + (doc['membership.status'].value == 'a' ? 2 : 0)
As a big aside, you should not be using dynamic scripting. Use stored scripts in production to avoid security issues.