Horton

Re: XML/XPath issues: text/CDATA in XMLTABLE, XPath evaluated with wrong context

Chapman Flack <chap@anastigmatix.net>

View thread View on postgr.es
From: Chapman Flack <chap@anastigmatix.net>
To: Ramanarayana <raam.soft@gmail.com>, Pavel Stehule <pavel.stehule@gmail.com>
Cc: Markus Winand <markus.winand@winand.at>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Alvaro Herrera <alvherre@2ndquadrant.com>
Date: 2019-03-01T01:31:04Z
Lists: pgsql-hackers 
Hi, thanks for checking the patches!

On 02/28/19 19:36, Ramanarayana wrote:
> The below statement needs to be executed before running the query to
> replicate the issue
> 
> update xmldata set data = regexp_replace(data::text, '791',
> '<!--ah-->7<!--oh-->9<!--uh-->1')::xml;

If you are applying that update (and there is a SIZE element originally
791), and then receiving a "more than one value returned by column XPath
expression" error, I believe you are seeing documented, correct behavior.

Your update changes the content of that SIZE element to have three
comment nodes and three text nodes.

The query then contains this column spec:

size_text float PATH 'SIZE/text()'

where the target SQL column type is 'float' and the path expression will
return an XML result consisting of the three text nodes.

As documented, "An XML result assigned to a column of any other type may
not have more than one node, or an error is raised."

So I think this behavior is correct.

If you do any more testing (thank you for taking the interest, by the way!),
could you please add your comments, not to this email thread, but to [1]?

[1]
https://www.postgresql.org/message-id/3e8eab9e-7289-6c23-5e2c-153cccea2257%40anastigmatix.net

That's the one that is registered to the commitfest entry, so comments made
on this thread might be overlooked.

Thanks!
-Chap

Commits

  1. Remove EState.es_range_table_array.

  2. Rationalize use of list_concat + list_copy combinations.

  3. Cosmetic improvements in setup of planner's per-RTE arrays.

  4. Make better use of the new List implementation in a couple of places

  5. Fix sepgsql test results for commit d97b714a2.

  6. Avoid using lcons and list_delete_first where it's easy to do so.

  7. Remove lappend_cell...() family of List functions.

  8. Clean up some ad-hoc code for sorting and de-duplicating Lists.

  9. Redesign the API for list sorting (list_qsort becomes list_sort).

  10. Remove dead code.

  11. Represent Lists as expansible arrays, not chains of cons-cells.

  12. Standardize some more loops that chase down parallel lists.

  13. Reimplement the linked list data structure used throughout the backend.