I agree with Julian. If we can backtick quote Hive's if and have an option for Hive users, it would be nice. But Hive made a mess, and there is precedent for IF. This makes from a cluster administration perspective, and even being a Hive user, as long as I had an option (with backticks) to allow me to move forward, I'd understand and accept the required changes.
John On Thu, Jun 30, 2016 at 12:00 PM, Julian Hyde <jh...@apache.org> wrote: > Even though it’s not standard, several other databases have DROP TABLE … > IF EXISTS (MySQL [1]; Postgres [2] and SQL Server 2016 [3] put the “IF > EXISTS” before the table name). I know there are problems with the IF > keyword clashing with the Hive “IF” function, but I think it would be crazy > to do “IIF EXISTS”. > > I’d block Hive’s “IF” function, frankly. They screwed up. No need to > propagate their mess into Drill. > > Julian > > [1] http://dev.mysql.com/doc/refman/5.7/en/drop-table.html < > http://dev.mysql.com/doc/refman/5.7/en/drop-table.html> > > [2] https://www.postgresql.org/docs/8.2/static/sql-droptable.html < > https://www.postgresql.org/docs/8.2/static/sql-droptable.html> > > [3] > https://blogs.msdn.microsoft.com/sqlserverstorageengine/2015/11/03/drop-if-exists-new-thing-in-sql-server-2016/ > < > https://blogs.msdn.microsoft.com/sqlserverstorageengine/2015/11/03/drop-if-exists-new-thing-in-sql-server-2016/ > > > > > On Jun 30, 2016, at 5:06 AM, Khurram Faraaz <kfar...@maprtech.com> > wrote: > > > > I looked at the SQL standard and I did not find that IF EXISTS is a part > of > > DROP TABLE syntax, please see below. > > > > INTERNATIONAL STANDARD > > ISO/IEC 9075-2 > > Fourth edition 2011-12-15 > > > > > > Format > > <drop table statement> ::= > > DROP TABLE <table name> <drop behavior> > > > > <drop behavior> ::= > > CASCADE > > | RESTRICT > > > > On Thu, Jun 30, 2016 at 3:44 PM, Arina Yelchiyeva < > > arina.yelchiy...@gmail.com> wrote: > > > >> To sum up currently we are facing two options: > >> > >> 1. Add IF as keyword. > >> Pros: > >> DROP TABLE / VIEW IF EXISTS will work > >> Cons: > >> if function (loaded from Hive) will stop working. In this case users > will > >> have two options: > >> a) surround if with backticks (ex: select `if`(condition,option1, > option2) > >> from table) > >> b) replace if function with case statement > >> > >> 2. Use IIF instead of IF > >> Pros: > >> if function will work, no backward compatibility issues. > >> Cons: > >> uncommon syntax for IF EXISTS statement > >> > >> So far none of this options seems to be ideal. > >> > >> Kind regards > >> Arina > >> > >> > >> On Wed, Jun 29, 2016 at 8:56 PM Paul Rogers <prog...@maprtech.com> > wrote: > >> > >>> Hi Vitalii, > >>> > >>> This will be a nice improvement. Your question about “IIF” vs. “IF” is > in > >>> the context of one small enhancement. But, it raises a larger question > >>> (which is beyond the scope of your project, but is worth discussing > >> anyway.) > >>> > >>> That larger issue is that we really should modify the Drill SQL parser > to > >>> better handle keywords vs. identifiers. That is, the following > >>> “pathological” statement should be valid: > >>> > >>> SELECT select, from FROM from, where WHERE from.select = where.from; > >>> > >>> This seems very confusing to us humans. But, to the SQL grammar the > above > >>> is unambiguous. SQL syntax determines where a keyword is valid. All > other > >>> uses of that keyword can easily be interpreted as an identifier. > Further, > >>> the location of the identifier determines whether to interpreted it as > a > >>> column, table, schema, function, etc. For example, a keyword will never > >>> appear in a select list, from list or where expression. Technically, we > >>> could introduce distinct name spaces for keywords, columns, tables, > >>> functions and so on. > >>> > >>> Without this change we run two risks: > >>> > >>> 1. We can’t use proper SQL syntax when we need it (as in your project.) > >>> 2. We risk breaking queries when we add new keywords (as in the dynamic > >>> UDF project.) > >>> > >>> This is not a new idea. Informix made this very change to their parser, > >>> for similar reasons — and did it back in the late ‘80s using C and YACC > >>> (for you old timers.) > >>> > >>> I’m not familiar with the Calcite parser. Anyone know what would be > >>> involved in making this change so Vitalii can use proper SQL syntax? > >>> > >>> - Paul > >>> > >>> > >>>> On Jun 29, 2016, at 10:15 AM, Vitalii Diravka < > >> vitalii.dira...@gmail.com> > >>> wrote: > >>>> > >>>> Hi all! > >>>> > >>>> I'm going to implement "DROP TABLE IIF EXISTS" and "DROP VIEW IIF > >> EXISTS" > >>>> statements in Drill (DRILL-4673 > >>>> <https://issues.apache.org/jira/browse/DRILL-4673>). > >>>> The reason of using "IIF" is inability of adding "IF" keyword to > >>>> non-reserved words list (due to SQL:2011 standard which calcite parser > >>>> uses). Adding of "IF" to reserved words list leads to not working hive > >>> "IF" > >>>> UDF. > >>>> > >>>> I'm interested are there any concerns with using "IIF" ? > >>>> > >>>> Kind regards > >>>> Vitalii > >>> > >>> > >> > >
