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Posted to dev@couchdb.apache.org by "Brian Candler (JIRA)" <ji...@apache.org> on 2009/04/28 11:08:30 UTC
[jira] Created: (COUCHDB-336) Would like errors in map function to
be reported to client
Would like errors in map function to be reported to client
----------------------------------------------------------
Key: COUCHDB-336
URL: https://issues.apache.org/jira/browse/COUCHDB-336
Project: CouchDB
Issue Type: Wish
Environment: svn trunk 0.10.0a768591
Reporter: Brian Candler
Priority: Minor
At the moment, if a runtime error occurs in a map function, the document is silently excluded from the view and the client is none the wiser.
$ curl -X PUT http://127.0.0.1:5984/test
{"ok":true}
$ curl -d '{"foo":"bar"}' -X PUT http://127.0.0.1:5984/test/doc1
{"ok":true,"id":"doc1","rev":"1-3413565576"}
$ curl -d '{"food":"bar"}' -X PUT http://127.0.0.1:5984/test/doc2
{"ok":true,"id":"doc2","rev":"1-2088327893"}
# Example 1: map function calls undefined function
$ curl -d '{"map":"function(doc) { emitt(null,null); }"}' -H 'Content-Type: application/json' -X POST http://127.0.0.1:5984/test/_temp_view
{"total_rows":0,"rows":[]}
# Example 2: map function attempts to emit 'undefined'
$ curl -d '{"map":"function(doc) { emit(doc._id,doc.foo); }"}' -H 'Content-Type: application/json' -X POST http://127.0.0.1:5984/test/_temp_view
{"total_rows":1,"offset":0,"rows":[
{"id":"doc1","key":"doc1","value":"bar"}
]}
Of course, errors are available in the server log:
[Tue, 28 Apr 2009 08:40:39 GMT] [info] [<0.1276.0>] OS Process Log Message: function raised exception (ReferenceError: emitt is not defined) with doc._id doc1
[Tue, 28 Apr 2009 08:43:44 GMT] [info] [<0.1276.0>] OS Process Log Message: function raised exception (Cannot encode 'undefined' value as JSON) with doc._id doc2
But the client cannot see these, and worse, gets what appears to be a valid result set.
I think there are two cases to consider.
- in temporary views, it ought to be easy to do something: e.g. (1) return the full set of failed docs with their errors, or (2) return a count of failed docs, or (3) just abort on the first error
- in permanent views, it might also be useful to return this information, but it could be expensive to persist. Also, when you're querying for key X you might not want to see a whole load of errors for unrelated docs. An error count might be OK though, similar to total_rows.
The current behaviour may be useful, although I personally wouldn't want to rely on it, especially as it generates errors in the log. That is, I would rather be forced to rewrite example 2 as
function(doc) { if (doc.foo) { emit(doc._id, doc.foo); } }
or
function(doc) { emit(doc._id, doc.foo || null); }
as appropriate.
Workaround: users can manually wrap each of their map functions in a catcher which emits a sentinel key/value pair containing the error. However they would still have to query the key range which includes the error messages.
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[jira] Commented: (COUCHDB-336) Would like errors in map function
to be reported to client
Posted by "Brian Candler (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/COUCHDB-336?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12706742#action_12706742 ]
Brian Candler commented on COUCHDB-336:
---------------------------------------
Strange,. When I replicate the logic from compileFunction() at the spidermonkey command line, it seems to catch the error just fine:
js> sandbox = evalcx('');
[object sandbox]
js> try { f = eval("function(doc){val val=doc.k; emit(val||null,null);}", sandbox); } catch (err) { print("OOPS: " + err); }
OOPS: SyntaxError: missing ; before statement
js> try { f = eval("function(doc){val val=doc.k; emit(val||null,null);}", sandbox); } catch (err) { print("OOPS: " + err.toString()); }
OOPS: SyntaxError: missing ; before statement
Maybe a js/spidermonkey expert can explain why this doesn't seem to work in main.js. Instead it falls through to the later test which checks whether typeof(functionObject) == "function"
> Would like errors in map function to be reported to client
> ----------------------------------------------------------
>
> Key: COUCHDB-336
> URL: https://issues.apache.org/jira/browse/COUCHDB-336
> Project: CouchDB
> Issue Type: Wish
> Environment: svn trunk 0.10.0a768591
> Reporter: Brian Candler
> Priority: Minor
>
> At the moment, if a runtime error occurs in a map function, the document is silently excluded from the view and the client is none the wiser.
> $ curl -X PUT http://127.0.0.1:5984/test
> {"ok":true}
> $ curl -d '{"foo":"bar"}' -X PUT http://127.0.0.1:5984/test/doc1
> {"ok":true,"id":"doc1","rev":"1-3413565576"}
> $ curl -d '{"food":"bar"}' -X PUT http://127.0.0.1:5984/test/doc2
> {"ok":true,"id":"doc2","rev":"1-2088327893"}
> # Example 1: map function calls undefined function
> $ curl -d '{"map":"function(doc) { emitt(null,null); }"}' -H 'Content-Type: application/json' -X POST http://127.0.0.1:5984/test/_temp_view
> {"total_rows":0,"rows":[]}
> # Example 2: map function attempts to emit 'undefined'
> $ curl -d '{"map":"function(doc) { emit(doc._id,doc.foo); }"}' -H 'Content-Type: application/json' -X POST http://127.0.0.1:5984/test/_temp_view
> {"total_rows":1,"offset":0,"rows":[
> {"id":"doc1","key":"doc1","value":"bar"}
> ]}
> Of course, errors are available in the server log:
> [Tue, 28 Apr 2009 08:40:39 GMT] [info] [<0.1276.0>] OS Process Log Message: function raised exception (ReferenceError: emitt is not defined) with doc._id doc1
> [Tue, 28 Apr 2009 08:43:44 GMT] [info] [<0.1276.0>] OS Process Log Message: function raised exception (Cannot encode 'undefined' value as JSON) with doc._id doc2
> But the client cannot see these, and worse, gets what appears to be a valid result set.
> I think there are two cases to consider.
> - in temporary views, it ought to be easy to do something: e.g. (1) return the full set of failed docs with their errors, or (2) return a count of failed docs, or (3) just abort on the first error
> - in permanent views, it might also be useful to return this information, but it could be expensive to persist. Also, when you're querying for key X you might not want to see a whole load of errors for unrelated docs. An error count might be OK though, similar to total_rows.
> The current behaviour may be useful, although I personally wouldn't want to rely on it, especially as it generates errors in the log. That is, I would rather be forced to rewrite example 2 as
> function(doc) { if (doc.foo) { emit(doc._id, doc.foo); } }
> or
> function(doc) { emit(doc._id, doc.foo || null); }
> as appropriate.
> Workaround: users can manually wrap each of their map functions in a catcher which emits a sentinel key/value pair containing the error. However they would still have to query the key range which includes the error messages.
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[jira] Commented: (COUCHDB-336) Would like errors in map function
to be reported to client
Posted by "Brian Candler (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/COUCHDB-336?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12706759#action_12706759 ]
Brian Candler commented on COUCHDB-336:
---------------------------------------
Sorry, my mistake for using eval instead of evalcx. The problem seems to be that evalcx silently catches and discards all errors:
js> evalcx('junk(');
js> evalcx('throw("wobbly")');
js> result = evalcx('throw("wobbly")');
js> typeof result
undefined
js>
I'll ask about this on dev-tech-javascript. At the moment, the only solution I can see is to eval() inside the evalcx(), which is ugly as it involves re-escaping the source string.
> Would like errors in map function to be reported to client
> ----------------------------------------------------------
>
> Key: COUCHDB-336
> URL: https://issues.apache.org/jira/browse/COUCHDB-336
> Project: CouchDB
> Issue Type: Wish
> Environment: svn trunk 0.10.0a768591
> Reporter: Brian Candler
> Priority: Minor
>
> At the moment, if a runtime error occurs in a map function, the document is silently excluded from the view and the client is none the wiser.
> $ curl -X PUT http://127.0.0.1:5984/test
> {"ok":true}
> $ curl -d '{"foo":"bar"}' -X PUT http://127.0.0.1:5984/test/doc1
> {"ok":true,"id":"doc1","rev":"1-3413565576"}
> $ curl -d '{"food":"bar"}' -X PUT http://127.0.0.1:5984/test/doc2
> {"ok":true,"id":"doc2","rev":"1-2088327893"}
> # Example 1: map function calls undefined function
> $ curl -d '{"map":"function(doc) { emitt(null,null); }"}' -H 'Content-Type: application/json' -X POST http://127.0.0.1:5984/test/_temp_view
> {"total_rows":0,"rows":[]}
> # Example 2: map function attempts to emit 'undefined'
> $ curl -d '{"map":"function(doc) { emit(doc._id,doc.foo); }"}' -H 'Content-Type: application/json' -X POST http://127.0.0.1:5984/test/_temp_view
> {"total_rows":1,"offset":0,"rows":[
> {"id":"doc1","key":"doc1","value":"bar"}
> ]}
> Of course, errors are available in the server log:
> [Tue, 28 Apr 2009 08:40:39 GMT] [info] [<0.1276.0>] OS Process Log Message: function raised exception (ReferenceError: emitt is not defined) with doc._id doc1
> [Tue, 28 Apr 2009 08:43:44 GMT] [info] [<0.1276.0>] OS Process Log Message: function raised exception (Cannot encode 'undefined' value as JSON) with doc._id doc2
> But the client cannot see these, and worse, gets what appears to be a valid result set.
> I think there are two cases to consider.
> - in temporary views, it ought to be easy to do something: e.g. (1) return the full set of failed docs with their errors, or (2) return a count of failed docs, or (3) just abort on the first error
> - in permanent views, it might also be useful to return this information, but it could be expensive to persist. Also, when you're querying for key X you might not want to see a whole load of errors for unrelated docs. An error count might be OK though, similar to total_rows.
> The current behaviour may be useful, although I personally wouldn't want to rely on it, especially as it generates errors in the log. That is, I would rather be forced to rewrite example 2 as
> function(doc) { if (doc.foo) { emit(doc._id, doc.foo); } }
> or
> function(doc) { emit(doc._id, doc.foo || null); }
> as appropriate.
> Workaround: users can manually wrap each of their map functions in a catcher which emits a sentinel key/value pair containing the error. However they would still have to query the key range which includes the error messages.
--
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[jira] Commented: (COUCHDB-336) Would like errors in map function
to be reported to client
Posted by "Paul Joseph Davis (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/COUCHDB-336?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12703745#action_12703745 ]
Paul Joseph Davis commented on COUCHDB-336:
-------------------------------------------
Chris Anderson had a patch that he was working on for this specifically. IIRC, his behavior was to throw an error at query time that reports the first error that was thrown from the map function. Not sure on the current status.
> Would like errors in map function to be reported to client
> ----------------------------------------------------------
>
> Key: COUCHDB-336
> URL: https://issues.apache.org/jira/browse/COUCHDB-336
> Project: CouchDB
> Issue Type: Wish
> Environment: svn trunk 0.10.0a768591
> Reporter: Brian Candler
> Priority: Minor
>
> At the moment, if a runtime error occurs in a map function, the document is silently excluded from the view and the client is none the wiser.
> $ curl -X PUT http://127.0.0.1:5984/test
> {"ok":true}
> $ curl -d '{"foo":"bar"}' -X PUT http://127.0.0.1:5984/test/doc1
> {"ok":true,"id":"doc1","rev":"1-3413565576"}
> $ curl -d '{"food":"bar"}' -X PUT http://127.0.0.1:5984/test/doc2
> {"ok":true,"id":"doc2","rev":"1-2088327893"}
> # Example 1: map function calls undefined function
> $ curl -d '{"map":"function(doc) { emitt(null,null); }"}' -H 'Content-Type: application/json' -X POST http://127.0.0.1:5984/test/_temp_view
> {"total_rows":0,"rows":[]}
> # Example 2: map function attempts to emit 'undefined'
> $ curl -d '{"map":"function(doc) { emit(doc._id,doc.foo); }"}' -H 'Content-Type: application/json' -X POST http://127.0.0.1:5984/test/_temp_view
> {"total_rows":1,"offset":0,"rows":[
> {"id":"doc1","key":"doc1","value":"bar"}
> ]}
> Of course, errors are available in the server log:
> [Tue, 28 Apr 2009 08:40:39 GMT] [info] [<0.1276.0>] OS Process Log Message: function raised exception (ReferenceError: emitt is not defined) with doc._id doc1
> [Tue, 28 Apr 2009 08:43:44 GMT] [info] [<0.1276.0>] OS Process Log Message: function raised exception (Cannot encode 'undefined' value as JSON) with doc._id doc2
> But the client cannot see these, and worse, gets what appears to be a valid result set.
> I think there are two cases to consider.
> - in temporary views, it ought to be easy to do something: e.g. (1) return the full set of failed docs with their errors, or (2) return a count of failed docs, or (3) just abort on the first error
> - in permanent views, it might also be useful to return this information, but it could be expensive to persist. Also, when you're querying for key X you might not want to see a whole load of errors for unrelated docs. An error count might be OK though, similar to total_rows.
> The current behaviour may be useful, although I personally wouldn't want to rely on it, especially as it generates errors in the log. That is, I would rather be forced to rewrite example 2 as
> function(doc) { if (doc.foo) { emit(doc._id, doc.foo); } }
> or
> function(doc) { emit(doc._id, doc.foo || null); }
> as appropriate.
> Workaround: users can manually wrap each of their map functions in a catcher which emits a sentinel key/value pair containing the error. However they would still have to query the key range which includes the error messages.
--
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[jira] Commented: (COUCHDB-336) Would like errors in map function
to be reported to client
Posted by "Chris Anderson (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/COUCHDB-336?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12706745#action_12706745 ]
Chris Anderson commented on COUCHDB-336:
----------------------------------------
Until recently there was a bug in the couchjs interpreter that caused any syntax error to result in a process exit. I've resolved that bug but haven't had a chance to see if we can do a better job reporting errors to the user. You should be able to make this cleaner just by hacking the files in share/server/
> Would like errors in map function to be reported to client
> ----------------------------------------------------------
>
> Key: COUCHDB-336
> URL: https://issues.apache.org/jira/browse/COUCHDB-336
> Project: CouchDB
> Issue Type: Wish
> Environment: svn trunk 0.10.0a768591
> Reporter: Brian Candler
> Priority: Minor
>
> At the moment, if a runtime error occurs in a map function, the document is silently excluded from the view and the client is none the wiser.
> $ curl -X PUT http://127.0.0.1:5984/test
> {"ok":true}
> $ curl -d '{"foo":"bar"}' -X PUT http://127.0.0.1:5984/test/doc1
> {"ok":true,"id":"doc1","rev":"1-3413565576"}
> $ curl -d '{"food":"bar"}' -X PUT http://127.0.0.1:5984/test/doc2
> {"ok":true,"id":"doc2","rev":"1-2088327893"}
> # Example 1: map function calls undefined function
> $ curl -d '{"map":"function(doc) { emitt(null,null); }"}' -H 'Content-Type: application/json' -X POST http://127.0.0.1:5984/test/_temp_view
> {"total_rows":0,"rows":[]}
> # Example 2: map function attempts to emit 'undefined'
> $ curl -d '{"map":"function(doc) { emit(doc._id,doc.foo); }"}' -H 'Content-Type: application/json' -X POST http://127.0.0.1:5984/test/_temp_view
> {"total_rows":1,"offset":0,"rows":[
> {"id":"doc1","key":"doc1","value":"bar"}
> ]}
> Of course, errors are available in the server log:
> [Tue, 28 Apr 2009 08:40:39 GMT] [info] [<0.1276.0>] OS Process Log Message: function raised exception (ReferenceError: emitt is not defined) with doc._id doc1
> [Tue, 28 Apr 2009 08:43:44 GMT] [info] [<0.1276.0>] OS Process Log Message: function raised exception (Cannot encode 'undefined' value as JSON) with doc._id doc2
> But the client cannot see these, and worse, gets what appears to be a valid result set.
> I think there are two cases to consider.
> - in temporary views, it ought to be easy to do something: e.g. (1) return the full set of failed docs with their errors, or (2) return a count of failed docs, or (3) just abort on the first error
> - in permanent views, it might also be useful to return this information, but it could be expensive to persist. Also, when you're querying for key X you might not want to see a whole load of errors for unrelated docs. An error count might be OK though, similar to total_rows.
> The current behaviour may be useful, although I personally wouldn't want to rely on it, especially as it generates errors in the log. That is, I would rather be forced to rewrite example 2 as
> function(doc) { if (doc.foo) { emit(doc._id, doc.foo); } }
> or
> function(doc) { emit(doc._id, doc.foo || null); }
> as appropriate.
> Workaround: users can manually wrap each of their map functions in a catcher which emits a sentinel key/value pair containing the error. However they would still have to query the key range which includes the error messages.
--
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[jira] Commented: (COUCHDB-336) Would like errors in map function
to be reported to client
Posted by "Paul Joseph Davis (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/COUCHDB-336?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12706224#action_12706224 ]
Paul Joseph Davis commented on COUCHDB-336:
-------------------------------------------
Error reporting like that is hard in JS. I've tried to do it for python-spidermonkey but haven't quite got it nailed down. Granted it was never quite at the top of the priority list. If you can provide a patch that mimics the code on the JS shell I'd give it a serious look to add to main.js but as I recall its a bit convoluted.
> Would like errors in map function to be reported to client
> ----------------------------------------------------------
>
> Key: COUCHDB-336
> URL: https://issues.apache.org/jira/browse/COUCHDB-336
> Project: CouchDB
> Issue Type: Wish
> Environment: svn trunk 0.10.0a768591
> Reporter: Brian Candler
> Priority: Minor
>
> At the moment, if a runtime error occurs in a map function, the document is silently excluded from the view and the client is none the wiser.
> $ curl -X PUT http://127.0.0.1:5984/test
> {"ok":true}
> $ curl -d '{"foo":"bar"}' -X PUT http://127.0.0.1:5984/test/doc1
> {"ok":true,"id":"doc1","rev":"1-3413565576"}
> $ curl -d '{"food":"bar"}' -X PUT http://127.0.0.1:5984/test/doc2
> {"ok":true,"id":"doc2","rev":"1-2088327893"}
> # Example 1: map function calls undefined function
> $ curl -d '{"map":"function(doc) { emitt(null,null); }"}' -H 'Content-Type: application/json' -X POST http://127.0.0.1:5984/test/_temp_view
> {"total_rows":0,"rows":[]}
> # Example 2: map function attempts to emit 'undefined'
> $ curl -d '{"map":"function(doc) { emit(doc._id,doc.foo); }"}' -H 'Content-Type: application/json' -X POST http://127.0.0.1:5984/test/_temp_view
> {"total_rows":1,"offset":0,"rows":[
> {"id":"doc1","key":"doc1","value":"bar"}
> ]}
> Of course, errors are available in the server log:
> [Tue, 28 Apr 2009 08:40:39 GMT] [info] [<0.1276.0>] OS Process Log Message: function raised exception (ReferenceError: emitt is not defined) with doc._id doc1
> [Tue, 28 Apr 2009 08:43:44 GMT] [info] [<0.1276.0>] OS Process Log Message: function raised exception (Cannot encode 'undefined' value as JSON) with doc._id doc2
> But the client cannot see these, and worse, gets what appears to be a valid result set.
> I think there are two cases to consider.
> - in temporary views, it ought to be easy to do something: e.g. (1) return the full set of failed docs with their errors, or (2) return a count of failed docs, or (3) just abort on the first error
> - in permanent views, it might also be useful to return this information, but it could be expensive to persist. Also, when you're querying for key X you might not want to see a whole load of errors for unrelated docs. An error count might be OK though, similar to total_rows.
> The current behaviour may be useful, although I personally wouldn't want to rely on it, especially as it generates errors in the log. That is, I would rather be forced to rewrite example 2 as
> function(doc) { if (doc.foo) { emit(doc._id, doc.foo); } }
> or
> function(doc) { emit(doc._id, doc.foo || null); }
> as appropriate.
> Workaround: users can manually wrap each of their map functions in a catcher which emits a sentinel key/value pair containing the error. However they would still have to query the key range which includes the error messages.
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[jira] Updated: (COUCHDB-336) Would like errors in map function to
be reported to client
Posted by "Paul Joseph Davis (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/COUCHDB-336?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Paul Joseph Davis updated COUCHDB-336:
--------------------------------------
Skill Level: Regular Contributors Level (Easy to Medium)
> Would like errors in map function to be reported to client
> ----------------------------------------------------------
>
> Key: COUCHDB-336
> URL: https://issues.apache.org/jira/browse/COUCHDB-336
> Project: CouchDB
> Issue Type: Wish
> Environment: svn trunk 0.10.0a768591
> Reporter: Brian Candler
> Priority: Minor
>
> At the moment, if a runtime error occurs in a map function, the document is silently excluded from the view and the client is none the wiser.
> $ curl -X PUT http://127.0.0.1:5984/test
> {"ok":true}
> $ curl -d '{"foo":"bar"}' -X PUT http://127.0.0.1:5984/test/doc1
> {"ok":true,"id":"doc1","rev":"1-3413565576"}
> $ curl -d '{"food":"bar"}' -X PUT http://127.0.0.1:5984/test/doc2
> {"ok":true,"id":"doc2","rev":"1-2088327893"}
> # Example 1: map function calls undefined function
> $ curl -d '{"map":"function(doc) { emitt(null,null); }"}' -H 'Content-Type: application/json' -X POST http://127.0.0.1:5984/test/_temp_view
> {"total_rows":0,"rows":[]}
> # Example 2: map function attempts to emit 'undefined'
> $ curl -d '{"map":"function(doc) { emit(doc._id,doc.foo); }"}' -H 'Content-Type: application/json' -X POST http://127.0.0.1:5984/test/_temp_view
> {"total_rows":1,"offset":0,"rows":[
> {"id":"doc1","key":"doc1","value":"bar"}
> ]}
> Of course, errors are available in the server log:
> [Tue, 28 Apr 2009 08:40:39 GMT] [info] [<0.1276.0>] OS Process Log Message: function raised exception (ReferenceError: emitt is not defined) with doc._id doc1
> [Tue, 28 Apr 2009 08:43:44 GMT] [info] [<0.1276.0>] OS Process Log Message: function raised exception (Cannot encode 'undefined' value as JSON) with doc._id doc2
> But the client cannot see these, and worse, gets what appears to be a valid result set.
> I think there are two cases to consider.
> - in temporary views, it ought to be easy to do something: e.g. (1) return the full set of failed docs with their errors, or (2) return a count of failed docs, or (3) just abort on the first error
> - in permanent views, it might also be useful to return this information, but it could be expensive to persist. Also, when you're querying for key X you might not want to see a whole load of errors for unrelated docs. An error count might be OK though, similar to total_rows.
> The current behaviour may be useful, although I personally wouldn't want to rely on it, especially as it generates errors in the log. That is, I would rather be forced to rewrite example 2 as
> function(doc) { if (doc.foo) { emit(doc._id, doc.foo); } }
> or
> function(doc) { emit(doc._id, doc.foo || null); }
> as appropriate.
> Workaround: users can manually wrap each of their map functions in a catcher which emits a sentinel key/value pair containing the error. However they would still have to query the key range which includes the error messages.
--
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[jira] Commented: (COUCHDB-336) Would like errors in map function
to be reported to client
Posted by "Brian Candler (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/COUCHDB-336?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12706200#action_12706200 ]
Brian Candler commented on COUCHDB-336:
---------------------------------------
As an additional point: the error messages currently returned for a badly-formed map or reduce function are not as good as the standalone js is capable of producing. For example:
$ curl -X POST -d '{"map":"function(doc){val val=doc.k; emit(val||null,null);}"}' http://127.0.0.1:5984/test/_temp_view
{"error":"compilation_error","reason":"expression does not eval to a function. (function(doc){val val=doc.k; emit(val||null,null);})"}
It's very common for a syntax error to return only "expression does not eval to a function". However, pasting the same code into js gives a much more informative error, indicating both the nature of the error and its location.
js> function(doc){val val=doc.k; emit(val||null,null);}
typein:1: SyntaxError: missing ; before statement:
typein:1: function(doc){val val=doc.k; emit(val||null,null);}
typein:1: ..................^
> Would like errors in map function to be reported to client
> ----------------------------------------------------------
>
> Key: COUCHDB-336
> URL: https://issues.apache.org/jira/browse/COUCHDB-336
> Project: CouchDB
> Issue Type: Wish
> Environment: svn trunk 0.10.0a768591
> Reporter: Brian Candler
> Priority: Minor
>
> At the moment, if a runtime error occurs in a map function, the document is silently excluded from the view and the client is none the wiser.
> $ curl -X PUT http://127.0.0.1:5984/test
> {"ok":true}
> $ curl -d '{"foo":"bar"}' -X PUT http://127.0.0.1:5984/test/doc1
> {"ok":true,"id":"doc1","rev":"1-3413565576"}
> $ curl -d '{"food":"bar"}' -X PUT http://127.0.0.1:5984/test/doc2
> {"ok":true,"id":"doc2","rev":"1-2088327893"}
> # Example 1: map function calls undefined function
> $ curl -d '{"map":"function(doc) { emitt(null,null); }"}' -H 'Content-Type: application/json' -X POST http://127.0.0.1:5984/test/_temp_view
> {"total_rows":0,"rows":[]}
> # Example 2: map function attempts to emit 'undefined'
> $ curl -d '{"map":"function(doc) { emit(doc._id,doc.foo); }"}' -H 'Content-Type: application/json' -X POST http://127.0.0.1:5984/test/_temp_view
> {"total_rows":1,"offset":0,"rows":[
> {"id":"doc1","key":"doc1","value":"bar"}
> ]}
> Of course, errors are available in the server log:
> [Tue, 28 Apr 2009 08:40:39 GMT] [info] [<0.1276.0>] OS Process Log Message: function raised exception (ReferenceError: emitt is not defined) with doc._id doc1
> [Tue, 28 Apr 2009 08:43:44 GMT] [info] [<0.1276.0>] OS Process Log Message: function raised exception (Cannot encode 'undefined' value as JSON) with doc._id doc2
> But the client cannot see these, and worse, gets what appears to be a valid result set.
> I think there are two cases to consider.
> - in temporary views, it ought to be easy to do something: e.g. (1) return the full set of failed docs with their errors, or (2) return a count of failed docs, or (3) just abort on the first error
> - in permanent views, it might also be useful to return this information, but it could be expensive to persist. Also, when you're querying for key X you might not want to see a whole load of errors for unrelated docs. An error count might be OK though, similar to total_rows.
> The current behaviour may be useful, although I personally wouldn't want to rely on it, especially as it generates errors in the log. That is, I would rather be forced to rewrite example 2 as
> function(doc) { if (doc.foo) { emit(doc._id, doc.foo); } }
> or
> function(doc) { emit(doc._id, doc.foo || null); }
> as appropriate.
> Workaround: users can manually wrap each of their map functions in a catcher which emits a sentinel key/value pair containing the error. However they would still have to query the key range which includes the error messages.
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