TAP MAXREC interpretation

[Pierre Fernique]

Dear TAP experts,

While testing the various TAP services accessible via Aladin Desktop, I 
discovered an interpretation of the MAXREC parameter that I hadn't 
anticipated, and I'm wondering about its validity.

For example, if I query MAST TAP HSC, with a MAXREC of 2M, I don't get 
the table I want, but an error as shown below.

https://mast.stsci.edu/vo-tap/api/v0.1/hsc/sync?REQUEST=doQuery&LANG=ADQL&*MAXREC=20000000*&QUERY=SELECT+table_name+FROM+TAP_SCHEMA.tables

<VOTABLE version="1.4" 
xsi:schemaLocation="http://www.ivoa.net/xml/VOTable/v1.3 
http://www.ivoa.net/xml/VOTable/v1.3">
    <DESCRIPTION>MAST VO TAP Service</DESCRIPTION>
    <RESOURCE type="results">
       <INFO name="QUERY_STATUS" value="ERROR">
*Error in query maxrec: ensure this value is less than or equal to 100000*
      </INFO>
    </RESOURCE>
</VOTABLE>

But I would have expected to receive the result correctly, possibly 
truncated (OVERFLOW mention) at the internal limit of the service (100000).

In fact, such an approach makes it difficult for the client to use 
MAXREC, except by trial and error appoach. Either it's too high and I 
get an error, or it's too low (but by how much) and I may not get the 
full result when I could have. And finally, if I don't specify a MAXREC, 
the server will apply the default value, even though I could have asked 
for more.

Any advice on how to deal with this problem?

Thanks
Pierre Fernique
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