In your opinion, in multi-clause DDL statements like alter table p partition (j<2 or j>0, k like "%", z = '') set uncached;
Should "z = ''" be a synonym for "z IS NULL" like it is in the single-clause DDL? On Wed, Jul 6, 2016 at 11:28 AM, Marcel Kornacker <[email protected]> wrote: > On Wed, Jul 6, 2016 at 10:20 AM, Jim Apple <[email protected]> wrote: >> Let me try to explain what is going on here. >> >> Currently, if a user wants to specify a null partition for a DDL >> operation, they write something like >> >> compute incremental stats incremental_null_part_key partition(p = NULL); > > We need to keep this working for the time being. > >> >> For an empty string, they could write: >> >> alter table t_part drop partition (j=2, s='') >> >> This is unfortunate, as nothing "equals" NULL, and empty strings are >> mapped to the NULL partition value. >> >> Amos has written a patch that allows DDL operations to work on more >> than one partition at a time. These look like: >> >> alter table p partition (j<2 or j>0, k like "%") set uncached; >> >> Here, the clauses separated by commas are ANDed together to make one >> clause. The question is whether these clauses, which now are clauses >> and not just strangley-interpreted-equality, should keep the old >> behavior or break existing queries. > > For these clauses we should use 'IS [NOT] NULL'. > >> >> On Wed, Jul 6, 2016 at 6:44 AM, Amos Bird <[email protected]> wrote: >>> This problem came from https://issues.cloudera.org/browse/IMPALA-1654 , CR >>> at https://gerrit.cloudera.org/#/c/1563/ . This patch will make general >>> predicates possible in most partition DDL operations. However, for NULL >>> partitions, the old KV way no longer works. Broken cases are <string >>> val>="" and <val>=null. This is due to the usage of HdfsPartitionPruner >>> which is used for Query time partition pruning. Should we keep the old way >>> of treating NULL partition as special cases? >>> >>> Amos
