ADQL-2.0 Erratum 2: Mathematical Functions' Table issuesAuthor: DAL WG | ||||||||
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< < | Date last changed: 2017-09-28 | |||||||
> > | Date last changed: 2017-10-09 | |||||||
RationaleIVOA DAL mailing list thread on July 2016 highlighted a possible issue with the description of the MOD function. Discussion went on also on this other thread. Subsequently a different thread highlighted other mismatches between Table 1 (Mathematical functions) descriptions and the ADQL-2.0 grammar. Here follows what emerged as possible erratum content from those discussions. MOD function description | ||||||||
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< < | Considering what current TAP-1.0 services using ADQL and the mathematical description of the modulo operator where | |||||||
> > | Considering what current TAP-1.0 services using ADQL implement and the usual SQL definition of the modulo operator: | |||||||
M % N = R
with
unsigned_integer x to be an optional argument (the seed) to the random mathematical function. This is not made explicit in the description in Table 1.
We suggest to amend the description changing the final "where x is a seed" into "where x is an optional seed" value.
ROUND optional places number
ADQL BNF grammar (pages 29-30 of ADQL-2.0) reports the signed_integer n of ROUND(x, n) to be an optional argument. This signed integer number of places to round the value of x to is not made explicit to be optional in Table 1 description. Also, as per SQL standard, it should default to 0 when not explicitly present.
We suggest to amend the description of round(x, n) in Table 1 by adding a final sentence reading "The integer n is optional and its value should default to 0.".
TRUNCATE optional places number
ADQL BNF grammar (page 30 of ADQL-2.0) reports the signed_integer n of TRUNCATE(x, n) to be an optional argument. This signed integer number of places to truncate the value of x to is not made explicit to be optional in Table 1 description. Also, as per SQL standard, it should default to 0 when not explicitly present.
We suggest to amend the description of truncate(x, n) in Table 1 by adding a final sentence reading "The integer n is optional and its value should default to 0.".
Erratum ContentTable 1 on page 8 of the ADQL-2.0 recommendation reports the following descriptions for the hereby discussed mathematical functions:
Impact AssessmentThe changes proposed by this erratum should impact no existing IVOA resource. Checks against the major TAP services show they already act following the behaviour here above described for the modulo function, while for the remaining 3 issues, all of them simply require some explicit wording in the description to follow the grammar constraints. Checks against a choice of RDBMS-es (PostgreSQL, MySQL, MariaDB, Apache Derby, HyperSQL and Oracle) shows the same behaviour too. See the mail threads referenced in the introduction of this page for details.<--
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