Extension talk:Cargo

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Changes to Cargo content via XML Import won't update tables?[edit]

We used the MediaWiki Import/Export special pages to allow mass changes to some pages holding Cargo content, but related tables didn't update afterwards unless we recreate data (or save individual pages) manually. Is this expected behavior, or have we done something wrong? Thanks!

--198.49.180.254 14:26, 4 May 2017 (UTC)

That sounds like a bug in Cargo - my guess is that Special:Import doesn't call the hook that Cargo relies on to know when a page has been re-saved. So maybe it's really a bug in MediaWiki; I don't know. Yaron Koren (talk) 14:47, 4 May 2017 (UTC)

Hiding the "where" column(s) (SOLVED)[edit]

Hi there. I'm trying to run a query to show a list of events - a personal timeline - on each character sheet, based on the person's name showing up in the event.

{{#cargo_query:
tables=EVENT
|fields=EVENT._pageName=Date, EVENT.EVENT_Description=Description, EVENT.EVENT_Characters
|where=EVENT.EVENT_Characters HOLDS "{{PAGENAME}}"
|format=dynamic table}}

The events show up fine, but the last column is redundant, and I'd like to hide it. Is there a way to have the output table not show a column that is needed only for the where clause? --Brilligtove (talk) 17:44, 12 March 2017 (UTC)

Just don't include it in the "fields" parameter - you can have fields in "where" that aren't in "fields". Yaron Koren (talk) 21:40, 12 March 2017 (UTC)
Blimey, that was easy. I definitely tried that at one point but had other syntax errors to deal with and didn't go back to try it again. Thanks!--Brilligtove (talk) 17:31, 13 March 2017 (UTC)

Creation of tables fails on last column[edit]

There is an SQL-error apparently when trying to create the last column defined:

Software:

Cargo 1.3, MW 1.27.1, PHP 5.6.30, MariaDB 10.0.29

Template:

{{#cargo_declare:_table=Knowledge_Bar_Foo
|Knowledge_HasInfoa = Wikitext
|Knowledge_HasInfob = Boolean
|Knowledge_HasInfoc = String
|Knowledge_HasInfod = Date
|Knowledge_HasInfoe = Date
|Knowledge_HasInfof = Boolean
|Knowledge_HasInfog = Boolean
|Knowledge_HasInfoh = Boolean
|Knowledge_HasInfol = Boolean
|Knowledge_HasInfom = Wikitext
|Knowledge_HasInfon = List (,) of Page
|Knowledge_HasInfoo = List (,) of Page
|Knowledge_HasInfop = List (,) of Page
|Knowledge_HasInfoq = List (,) of String
|Knowledge_HasInfor = List (,) of String
|Knowledge_HasInfos = List (,) of Page
}}

Error:

php cargoRecreateData.php --table Knowledge_Bar_Foo
Recreating data for Cargo table Knowledge_Bar_Foo in 5 seconds... hit [Ctrl]-C to escape.
Deleting and recreating table...
A database query error has occurred.
Query: CREATE TABLE `MyPrefix_cargo__Knowledge_Bar_Foo__Knowledge_HasInfos` ( `_rowID` Int, `_value` Varchar(300) )
Function: DatabaseBase::query
Error: 1103 Incorrect table name 'MyPrefix_cargo__Knowledge_Bar_Foo__Knowledge_HasInfos' (localhost)

This operation also fails via the GUI. Help appreciated. --91.65.247.224 16:26, 17 March 2017 (UTC)

That's odd... I have no idea. Especially not why it fails on that table/column, and not on the previous ones. Could you try removing that "HasInfos" line from #cargo_declare, and see if it works without it? Yaron Koren (talk) 17:13, 17 March 2017 (UTC)
Turns out that we ran into multiple issues here.
Underscores cannot be used to define a field so the template must be like this and things roll:
{{#cargo_declare:_table=Knowledge_Bar_Foo
|KnowledgeHasInfoa = Wikitext
|KnowledgeHasInfob = Boolean
|KnowledgeHasInfoc = String
|KnowledgeHasInfod = Date
|KnowledgeHasInfoe = Date
|KnowledgeHasInfof = Boolean
|KnowledgeHasInfog = Boolean
|KnowledgeHasInfoh = Boolean
|KnowledgeHasInfol = Boolean
|KnowledgeHasInfom = Wikitext
|KnowledgeHasInfon = List (,) of Page
|KnowledgeHasInfoo = List (,) of Page
|KnowledgeHasInfop = List (,) of Page
|KnowledgeHasInfoq = List (,) of String
|KnowledgeHasInfor = List (,) of String
|KnowledgeHasInfos = List (,) of Page
}}
So the script probably already failed on the lines before but silently because of the second issue we got a visible error:
The second issue was that on the same template #cargo_store did not have a line for the KnowledgeHasInfos field so I got
PHP Notice:  Undefined index: KnowledgeHasInfos in /extensions/Cargo/parserfunctions/CargoStore.php on line 293
Notice: Undefined index: KnowledgeHasInfos in /extensions/Cargo/parserfunctions/CargoStore.php on line 293
Same for line 315 of that file.
It seems to be working now. Thanks for the suggestion which helped track down the issue. --91.65.247.224 09:09, 19 March 2017 (UTC)
Still out of luck. Now I get
[7450cee4a6402af82ba10421] /wiki/Special:CargoTables/Knowledge_Bar_Foo MWException from line 526 of /extensions/Cargo/CargoSQLQuery.php: Error: no field named "" found for any of the specified database tables.

Backtrace:

#0 /extensions/Cargo/specials/CargoTables.php(101): CargoSQLQuery->setDescriptionsForFields()
#1 /includes/specialpage/SpecialPage.php(479): CargoTables->execute(string)
#2 /includes/specialpage/SpecialPageFactory.php(576): SpecialPage->run(string)
#3 /includes/MediaWiki.php(282): SpecialPageFactory::executePath(Title, RequestContext)
#4 /includes/MediaWiki.php(735): MediaWiki->performRequest()
#5 /includes/MediaWiki.php(509): MediaWiki->main()
#6 /index.php(43): MediaWiki->run()
#7 {main}
--91.65.247.224 09:16, 19 March 2017 (UTC)
Removing all the blancs from #cargo_declare and #cargo_store does not help either. I also created a second template KnowledgeFooBar but this special page still fails. --91.65.247.224 09:24, 19 March 2017 (UTC)
Actually, field names can contain underscores. Can you run regular #cargo_query calls on this table, or do those fail as well? Yaron Koren (talk) 22:52, 19 March 2017 (UTC)
Turns out I told only half of the fun regarding "#cargo_declare" and "#cargo_store". Both functions contained invalid characters like umlauts when declaring fields. Now after only using characters MySQL can handle in names things seem to work. Three wishes if possible from what I have learned now: 1. The user or at least the sysop should get a warning that invalid characters were used, 2. the user/sysop should get a warning that the fields specified with both functions should match in name and number and 3. cargoRecreateData.php or a new script should have an option to delete tables if no longer used on the wiki. --91.65.247.224 15:38, 27 March 2017 (UTC)
Ah - that makes sense. #1 is a very good idea - I should have added that check in a long time ago. #2 I'm not sure is possible, unfortunately. For #3 - you should be able to delete any table at the page Special:CargoTables. Is this table not showing up there? Or would you prefer to do this from the command line in any case? Yaron Koren (talk) 15:54, 27 March 2017 (UTC)
I figured that 2 might be pretty tricky. For 3 yes, I prefer to have a command line option. If there is a listing option for cargo tables this will be nice too. --91.65.247.224 16:04, 27 March 2017 (UTC)

Okay, I looked into this, and it turns out that MySQL - and thus Cargo - can handle accented characters in table and field names. There was just a bug in the code that caused the error message you saw. I just checked in a fix for it, so if you get the latest code, you may be able to go back to the field names you used to have. Yaron Koren (talk) 02:17, 28 March 2017 (UTC)

Sorry that it took a while. No the issue caused by e.g. umlauts is still there using current master (d54c207) of Cargo. --91.65.247.224 17:30, 7 April 2017 (UTC)
That's not good. What's the exact error message you see? Yaron Koren (talk) 18:38, 7 April 2017 (UTC)
It is basically the same error but from another line:
[203dd3ab9e2c92b6eab6cd24] /wiki/Special:CargoTables/Knowledge_Bar_Foo MWException from line 565 of /.../w/extensions/Cargo/CargoSQLQuery.php: Error: no field named "" found for any of the specified database tables.

Backtrace:

#0 /.../w/extensions/Cargo/specials/CargoTables.php(115): CargoSQLQuery->setDescriptionsForFields()
#1 /.../w/includes/specialpage/SpecialPage.php(479): CargoTables->execute(string)
#2 /.../w/includes/specialpage/SpecialPageFactory.php(577): SpecialPage->run(string)
#3 /.../w/includes/MediaWiki.php(282): SpecialPageFactory::executePath(Title, RequestContext)
#4 /.../w/includes/MediaWiki.php(735): MediaWiki->performRequest()
#5 /.../w/includes/MediaWiki.php(509): MediaWiki->main()
#6 /.../w/index.php(43): MediaWiki->run()
#7 {main}
--91.65.247.224 16:52, 25 April 2017 (UTC)
That's too bad. This is actually the same line, unfortunately - it's just that other parts of the code have moved around. What is the name of the field that is causing the problem, do you know? Yaron Koren (talk) 19:33, 25 April 2017 (UTC)
A bit sad. I just run cargoRecreateData.php after upgrading to 1.3.1 and it ends without issues. The issue when trying to access the special page on wiki remains the same. Withing the template I do not really see what could cause the issue. No special chars etc. --91.65.247.224 14:15, 17 May 2017 (UTC)
Could you email me the template definition - or pastebin it and link to it here? Yaron Koren (talk) 16:06, 17 May 2017 (UTC)
Here we are. --91.65.247.224 16:33, 17 May 2017 (UTC)

Aha! That's very helpful. My fix for the previous problem with non-ASCII characters ended up causing a problem with fields with numbers in their name. I just checked in a fix, so hopefully now everything works - ASCII and non-ASCII characters alike. At least, I hope so. Yaron Koren (talk) 17:40, 17 May 2017 (UTC)

Great that this was of help. Sometimes the small things can be troubling. Affirmative, current master of Cargo makes the issue go away. Thank you for the fix! --91.65.247.224 15:43, 18 May 2017 (UTC)

Pre- and post-nominal letters for surnames in List of String[edit]

I have several pages, relating to court cases, each of which was decided by one or more judges.

The judges have pre-nominal (e.g. DJ Bloggs or HHJ Bloggs) or post-nominal (e.g. Bloggs J or Bloggs LJ) letters.

I would like to display the full title for the judge on each case page, but use Special:Drilldown on the surname.

The reason for this is that, although the surname is unique, the letters may change over time (e.g. in a 2000 case it may be Bloggs J, but the same judge in 2010 may be Bloggs LJ).

What would be the best way to implement this?

I had thought of using three fields, all Lists of String, for pre-nominal, surname, post-nominal, but I don't think there is any way to manipulate the individual results of Lists (in order to display pre-nominal + surname + post-nominal in a template).

Alternatively I could maybe use a list of wikitext like "[[Bloggs]] J, [[Jones]] J" and in the judge surname pages have a template query using HOLDS LIKE on the surname, but this wouldn't help with the Special:Drilldown interface.

Any ideas would be very welcome :-) Jonathan3 (talk) 22:58, 20 April 2017 (UTC)

Are there going to be pages for the judges? Or would you have that only if it's necessary for filtering? And why filter on, say, "Jones", instead of "Jones, J"? What if there's more than one Jones? Yaron Koren (talk)
Third attempt at replying. The mobile site crashed on my iPad...
I don't plan to have a page per judge. Ideally I'll write that code for you to have Miga-like links as an option for lists of strings etc. But more limited functionality could be provided by a judge page which lists each relevant case page. Perhaps automatically-created?
A judge's pre- or post-nominal letters may change over time so it would be much better (easier, less prone to error) to be able to filter on name only. Or have a way of linking each one so that filtering on one automatically includes the others. For example, HHJ Jones, Jones J and Jones LJ may be the same person.
At each level a more junior judge uses his Christian name (in addition to surname) as disambiguation if there is another judge with the same surname. There may be ambiguities between levels - I am not sure - but I have never seen this, and would be happy to proceed on the basis that it's unlikely and I could add Christian names for disambiguation on my website if it became necessary.
Perhaps the simplest solution/workaround would be to use name only in the list of string (for filtering etc) but have an extra text field for the [name with] correct pre- or post-nominal letters for the judge(s) on each individual case page. That has its advantages - mainly flexibility, e.g. strictly "Jones and Bloggs JJ" is correct whereas "Jones J, Bloggs J" is wrong - but it's still not my preferred option. Jonathan3 (talk) 10:18, 21 April 2017 (UTC)
Alright. It seems to me that the right answer is a variant on your idea at the end - have a Text field for the exact wording of the authors list, and have a separate field, holding a list of Strings, for however you want to store the information as data, whether it's last names only or anything else. It's redundant, but it seems like the easiest approach. Yaron Koren (talk) 12:28, 21 April 2017 (UTC)
Thanks. I'll give that a go. Jonathan3 (talk) 21:04, 23 April 2017 (UTC)

Hierarchies and categories[edit]

I have some plain wiki pages which I would like to convert to using Cargo. I am using four sets of categories per page. Three of these can easily be changed to Cargo fields (e.g. year). But the fourth category, in relation to the page subject matter, is part of a hierarchy which can be browsed by Extension:CategoryTree. I see from Extension:Cargo/Known bugs and planned features that a hierarchical structure for fields is not currently possible, but what could I do in the meantime?

Would it be possible to have a field containing a List of String, corresponding to the existing subject matter categories, which could be used in a template to put pages into categories? If so, it would have the twin benefits of allowing the categories to be browsed by CategoryTree, and allowing for them (via the field) to be browsed using Cargo's drilldown page. What would be the best way of implementing this? Thanks in advance. Jonathan3 (talk) 21:03, 23 April 2017 (UTC)

Yes, that's possible - use the tree input type to select the values within the form, and then use #arraymap in the template to create a category tag for each value (see the "For category names" subsection in that link). Yaron Koren (talk) 23:48, 23 April 2017 (UTC)
Thanks. The tree input type example on DiscourseDB briefly flashes up on my iPad Safari normally (with a category structure) but then ends up showing empty check/radio box inputs. Otherwise it looks like what I need and I guess it works on a "real computer". Jonathan3 (talk) 21:19, 24 April 2017 (UTC)
Oh, I had no idea that "tree" failed on the iPad - I'll have to look into that. Yaron Koren (talk) 01:43, 25 April 2017 (UTC)
The same thing happens when I try on various browsers on the PC. Maybe I am selecting the wrong option. The URL is: http://discoursedb.org/wiki/Special:FormEdit/Category_input_test/Testing Jonathan3 (talk) 00:01, 27 April 2017 (UTC)
Oops! I made a change to the code last week that clearly broke the "tree" input - sorry about that. I just checked in what I think is a fix. Yaron Koren (talk) 02:41, 27 April 2017 (UTC)

Cargo query on Drilldown page[edit]

It would be good if it were possible to add a Cargo query (or template containing one) to the Drilldown page. For instance, for one table I'd like it to show a map, and for another table I'd like it to show the "summary" field from the relevant pages. Is this something that would be possible in future? Jonathan3 (talk) 21:55, 26 April 2017 (UTC)

It would be great to show a map if the table has a Coordinates field - it's actually one of the planned features to have that done automatically. Allowing additional display fields is an interesting idea - Semantic Drilldown has that feature, so it's not inconceivable. Yaron Koren (talk) 02:57, 27 April 2017 (UTC)

timeline display format displays blank[edit]

I'm using a Referata wiki with Cargo. The timeline display format used to work, but now displays blank. (The calendar display format does work, but is not useful for my purposes, since I want to be able to scroll quickly over a span of at least 60 years.) Please confirm that timeline should work (it does work on the example given in the Extension:Cargo/Display formats page), and if so, suggest what I might try to get it to work again. I tried each Skin option and each Date format option, with the same blank result in each case.--Egnatoff (talk) 16:32, 29 April 2017 (UTC)

What's the URL with the problem? If you don't want to share the URL, what's the query? Yaron Koren (talk) 14:10, 30 April 2017 (UTC)
Here's the URL of the query page: Even Timeline and here's the query:
==Concerts by Date==
{{#cargo_query:
tables=Concerts|fields=_pageName,ConcertDate|order by=ConcertDate|order by=ConcertDate
|format=timeline|height=200! 
}}

--Egnatoff (talk) 01:35, 2 May 2017 (UTC)

Oops! It looks like "timeline" has been broken for a while. I just fixed it, I think, on Referata (that's the nice thing about having access to the server where the problem is). I also plan to check in this fix. Yaron Koren (talk) 03:09, 2 May 2017 (UTC)
Hurray! Thank you very much. I will have several thousand events so the timeline display will be a very important browsing mechanism.--Egnatoff (talk) 02:32, 3 May 2017 (UTC)

Cargo table list coordination problem[edit]

Example: Music concert database

Problem: Coordinating two lists from different tables—ensuring they match on data entry, and displaying them nicely. In particular, instruments are listed in the Pieces table and performers are listed in the PiecePerformances table. They need to match.

Tables in question: Field1 (type), Field 2 (type), . . .

Pieces: Page, Composer (page), Title, . . . (where Page is calculated: Title—Composer)

PiecePerformances: Page, Piece (page), Concert (page), Performers (list of page) (where Page is called: Piece performed at Concert)

Concerts: Page, SeriesTitle (page), Title, ConcertDate, ConcertTime, etc.(where Page is calculated: SeriesTitle—Title—ConcertDate)

A concert page displays all the PiecePerformances for that concert.

Here are the two things I haven’t figured out how to do:

1. A pieceperformance page should display the performers along with the instrument(s) that each performer plays, something like this:

performer1 (instrument1) - performer2 (instrument2) - . . .

2. I would like the data entry form for a piece performance to take the entered name of the piece and then get and display for that piece each instrument, with a box for entering the corresponding performer. That would seem to be a two-step process.--Egnatoff (talk) 03:24, 30 April 2017 (UTC)

If I understand the problem, you want to define some piece as a duet for flute and bassoon, and then, every time someone fills out a form for some performance of that piece, you want to have pre-set fields for "Flute:" and "Bassoon:". If that's correct, unfortunately there's no easy way to do that. The only approach I can think of involves the Scribunto extension, and dynamically-generated forms. I would think it's better, though, to just have editors enter the instruments and musicians every time themselves (using a multiple-instance template). It's more work for editors, but then again it's a more foolproof system. What if someone decides to perform that piece on glockenspiel instead? It's still the same piece, isn't it? Yaron Koren (talk) 14:28, 30 April 2017 (UTC)
That's certainly a more direct solution to the main problem, and would accommodate cases where instruments are changed, and whether or not there is a conductor. Point taken, thanks.--Egnatoff (talk) 18:48, 30 April 2017 (UTC)

Hidden parameter[edit]

The documentation at Extension:Cargo/Storing_data states, in relation to the "hidden" parameter:

"hidden - takes no value. If set, the field is not listed in either Special:ViewTable or Special:Drilldown, although it is still queriable."

I added "(hidden)" to some fields in an existing table and recreated the data. This prevented those fields from appearing in Special:Drilldown, but they still appear in Special:CargoTables. To be honest, this is what I would like to happen, but it does not match the documentation. Maybe this is just something which applies only when an existing table is recreated. Incidentally, I think "Special:ViewTable" should be changed to "Special:CargoTables". Jonathan3 (talk) 23:05, 1 May 2017 (UTC)

Those were indeed some bugs in the documentation. I think I just fixed them. Thanks! Yaron Koren (talk) 02:06, 2 May 2017 (UTC)

Duplicates Every Time[edit]

I updated to the latest version via git this morning to get rid of an error with getNamespace, and now every thing seems to make two entries.

Templates defined on the page multiple times, as well as templates that are just defined once per page. Example

Clearing the table and then re-populating does seem to clear up the issue.--Cody3647 (talk) 20:41, 2 May 2017 (UTC)

I don't know what's causing this; it could be some difference in storage between your old version and the current one. I would suggest just recreating all the tables; if that doesn't fully solve the issue, let me know. Yaron Koren (talk) 20:57, 2 May 2017 (UTC)
I have a similar problem using Cargo to store external data. Any new entry added to the database is fine and gets stored once. As soon as I re-save an existing data record by editing the page, the database starts to hold multiple copies of the entry (sometimes 2, sometimes 3). As if the old saved versions are not deleted. Using 'recreate data' through a browser cleans up the multiple entries of any records and it's fine again. However, I don't want to 'recreate data' every time a entry get's modified. Any idea what might go wrong? Used PageForm to get external data: http://csdms.colorado.edu/wiki/Form:Reference-auto1. --Albert Ke (talk) 16:48, 8 May 2017 (UTC)
(Cargo version: latest (installed May 1st); MW 1.28.1; PHP 5.6.30(fpm-fcgi); mysql 5.6.23-log)
Does this happen for every form, or just this one? And does it happen on every page save? Yaron Koren (talk) 19:54, 8 May 2017 (UTC)
I only made 1 pf using cargo, so not sure. Will do a test on that. Happens for every entry after I re-save that entry. --Albert Ke (talk) 21:42, 8 May 2017 (UTC)
Sorry this took a while. I created a very basic Page Form example using cargo to define & store just 1 field and I'm having the same issue: I can create a new entry for the database and it will be stored once. However, editing this page again using 'Edit with form' and this entry results in 3 data rows to the same page. I did test to see if it matters using instead of 'Edit with form' the wiki 'edit', and it does, now cargo will keep it to 1 data row. The used form: http://csdms.colorado.edu/wiki/Form:TestCargo The used template to define, store and show cargo data: http://csdms.colorado.edu/wiki/Template:HoldName. Any idea what I'm doing wrong? --Albert Ke (talk) 22:18, 12 May 2017 (UTC)
SOLVED (at least for me). Thank you Yaron for solving this problem. I had included a 'namespace' and 'query' statement in the '#formlink' definition and both shouldn't be there. Now data just get stored once, also after editing using the 'Edit with form' option. Many thanks Yaron!!! --Albert Ke (talk) 15:07, 14 May 2017 (UTC)
It's great that that fixed it! Although my guess is that it was actually the removal of both namespace settings in the form's page name formula, in this edit, that solved the problem. That's just a hunch, though. It's worth looking into this further, at some point. Yaron Koren (talk) 01:01, 15 May 2017 (UTC)

Importing data (e.g. from Access)[edit]

I have been sent a database which would be too big to enter into Cargo manually. Is there any way to import automatically? I guess I would need an extension/bot to create the necessary wiki pages. Jonathan3 (talk) 22:30, 3 May 2017 (UTC)

Yes - use the Data Transfer extension. Yaron Koren (talk) 00:49, 4 May 2017 (UTC)

Storage of lists: how to store and query for the order of values[edit]

I later need to sort and query by the order in which the template instances are appearing in a wiki page. In other words, the order of appearance represents the priority, and it is easy to implement drag-and-drop with Extension:Page_Forms.

Now I wonder how to get the ordering information into Cargo's database for later query.

The templates are hopefully stored in the database in the same order in which they appear on the page, so you may be able to accomplish this by just sorting on the "_ID" field. If that doesn't work, you may need to install the NumerAlpha extension, and add a new field to that multiple-instance template, setting the field to the value of #counter within #cargo_store. (Let me know if that doesn't make sense.) Yaron Koren (talk) 01:33, 8 May 2017 (UTC)

"Illegal mix of collations" error [RESOLVED][edit]

Here is an error from Cargo:

A database error has occurred. Did you forget to run maintenance/update.php after upgrading? See: https://www.mediawiki.org/wiki/Manual:Upgrading#Run_the_update_script
Query: SELECT `Description` AS `Description` FROM `wm_cargo__Event` WHERE _pageName="‎<event name>" ORDER BY `Description` LIMIT 100 Function: CargoSQLQuery::run Error: 1267 Illegal mix of collations (latin1_swedish_ci,IMPLICIT) and (utf8_general_ci,COERCIBLE) for operation '=' (<MySQL host URL>)

Here's what happened next:

  • I changed the title of the event page, to something purely alphabetical, which made the error go away.
  • I then changed it back to the original title, and the error came back.
  • Finally, I changed it to a slightly different version of the original (just by changing a small c to a capital C) and the error went away again.
  • Even now, having deleted the page with the original title, a Cargo query on the original title returns the same error, which I guess this because MediaWiki has saved the page title as a deleted page.

I can't think what caused this problem, which has not happened before. I wonder whether it may be has to do with the two changes necessary to the the auto complete work (which you suggested above). In that case I suppose the answer would be to update Page Forms properly.

My Cargo database tables are all latin1_swedish_ci but my MediaWiki database tables have ended up being a mixture of latin1_swedish_ci and utf8_general_ci. I asked about this here before and the answer was, sensibly enough, along the lines of "if it ain't broke don't fix it"... But now I wonder whether I should perhaps look into this properly.

Do you think this might be a Cargo thing, or a particular problem with my installation? Thanks in advance. Jonathan3 (talk)

It's not surprising that the query fails regardless of whether the page exists or not - this query is just accessing a single Cargo table, and doesn't look at the core MediaWiki data at all. So everything has to do with the page name, which I don't know. Though it could well be that replacing the double quotes in the query's "where" clause with single quotes would fix the issue also - I would definitely try that. Yaron Koren (talk) 14:30, 9 May 2017 (UTC)
The name was alphabetic except for a colon and a hyphen (never caused a problem before and other pages are similar without errors). When I do the same query with a page which never existed it says No results but gives no error. I'll try to look into the problem today or tomorrow. Jonathan3 (talk) 17:36, 9 May 2017 (UTC)
I am completely stumped! I can't do anything to make the error appear today. Jonathan3 (talk) 12:50, 10 May 2017 (UTC)
I think have found the source of the error :-) When I cut and paste the page title from the page itself, or from Special:Recentchanges the query works fine. The error only appears when I cut and paste the page title from Special:Newpages - when I put a page title from this source into an online Charset Decoder it looks fine as UTF-8 but there is an extra ‎ before the page title in ANSI. Jonathan3 (talk) 01:03, 23 May 2017 (UTC)
Ah, an invisible character... very annoying, and very hard to debug. I'm glad you were able to find this one. Yaron Koren (talk) 02:06, 23 May 2017 (UTC)
Cheers. It happens every time a page name is cut and pasted from Newpages, including from Wikipedia itself. Jonathan3 (talk) 18:40, 23 May 2017 (UTC)