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Zachary Whitley
Nov 8, 2016, 10:01:51 AM11/8/16
to Stardog
I think I've come across a bug in virtual graphs mappings. I apologize that I can't be more specific but I'm surprised I was even able to identify it. I was working on a mapping from MySQL and kept getting an "Error in identifying column name". I carefully followed the advice given here [1],[2] but still kept having problems. I happen to format my SQL in an indented style like the following
"SELECT
a,
b,
c
WHERE
a > 3"
I was guessing that there might be some soft of strange white space problem so I added spaces after SELECT, c, and WHERE and it fixed the problem. I only needed to do that on a couple of the queries and not all of them. I'll see if I can reproduce the problem but it might take me a little bit since I can't send the example I'm working on and I'd need to setup mysql, create a contrived example and data and hope that I can reproduce it. I thought I'd report it just in case anyone else comes across it and is banging their head on the table and wants to try what I did to see if it fixes the problem.
On a side note on my experiences working with mappings, I've found that it can be very challenging to debug SQL query problems especially when there are more than a handful of mappings. From the error message it's very difficult to identify what mapping was causing the problem. It would be nice if there was a way to step through the mappings to figure out which one was causing the problem.
[1] https://github.com/ontop/ontop/wiki/ObdalibPluginTroubleshooting#MySQL_Server_does_not_support_double_quotes_as_identifiers
[2] https://github.com/ontop/ontop/wiki/Case-sensitivity-for-SQL-identifiers
"SELECT
a,
b,
c
WHERE
a > 3"
I was guessing that there might be some soft of strange white space problem so I added spaces after SELECT, c, and WHERE and it fixed the problem. I only needed to do that on a couple of the queries and not all of them. I'll see if I can reproduce the problem but it might take me a little bit since I can't send the example I'm working on and I'd need to setup mysql, create a contrived example and data and hope that I can reproduce it. I thought I'd report it just in case anyone else comes across it and is banging their head on the table and wants to try what I did to see if it fixes the problem.
On a side note on my experiences working with mappings, I've found that it can be very challenging to debug SQL query problems especially when there are more than a handful of mappings. From the error message it's very difficult to identify what mapping was causing the problem. It would be nice if there was a way to step through the mappings to figure out which one was causing the problem.
[1] https://github.com/ontop/ontop/wiki/ObdalibPluginTroubleshooting#MySQL_Server_does_not_support_double_quotes_as_identifiers
[2] https://github.com/ontop/ontop/wiki/Case-sensitivity-for-SQL-identifiers
Jess Balint
Nov 8, 2016, 1:39:16 PM11/8/16
to sta...@clarkparsia.com
Hi Zach,
You're using the Stardog mapping syntax, correct?
Jess
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Zachary Whitley
Nov 8, 2016, 1:42:53 PM11/8/16
to Stardog
After adding the extra white space it works as expected so it shouldn't be a problem with the syntax. That might be interesting to try converting it to R2RML and see if it still has the same sensitivity to white space.
On Tue, Nov 8, 2016 at 1:39 PM, Jess Balint <je...@stardog.com> wrote:
Hi Zach,You're using the Stardog mapping syntax, correct?Jess
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Jess Balint
Nov 8, 2016, 1:52:10 PM11/8/16
to sta...@clarkparsia.com
Is it a multi-line string in Turtle syntax?
On Tue, Nov 8, 2016 at 12:42 PM, Zachary Whitley <zachary...@wavestrike.com> wrote:
After adding the extra white space it works as expected so it shouldn't be a problem with the syntax. That might be interesting to try converting it to R2RML and see if it still has the same sensitivity to white space.
On Tue, Nov 8, 2016 at 1:39 PM, Jess Balint <je...@stardog.com> wrote:
Hi Zach,You're using the Stardog mapping syntax, correct?Jess
Zachary Whitley
Nov 8, 2016, 2:46:48 PM11/8/16
to Stardog
It is but it's enclosed by three double quotes.
On Tue, Nov 8, 2016 at 1:52 PM, Jess Balint <je...@stardog.com> wrote:
Is it a multi-line string in Turtle syntax?
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