Agree with the last decision to use "IF EXISTS" statement and `if` udf with backticks. It is acceptable option.
Thank you for valuable advices. Kind regards Vitalii 2016-06-30 17:22 GMT+00:00 John Omernik <[email protected]>: > 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 <[email protected]> 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 <[email protected]> > > 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 < > > > [email protected]> 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 <[email protected]> > > 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 < > > >> [email protected]> > > >>> 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 > > >>> > > >>> > > >> > > > > >
