I have opened https://issues.apache.org/jira/browse/HIVE-20287 and would love to get feedback
On Wed, Aug 1, 2018 at 11:14 AM, Lars Francke <lars.fran...@gmail.com> wrote: > Thanks Lefty! I haven't created a JIRA but it's on my list. > > Still interested in any input anyone might have? > > Some of you guys _must_ have some knowledge on this stuff. > > You're correct that the DROP stuff is documented. What I meant is that I > couldn't find the relevant parts in the code. > > On Sat, Jul 21, 2018 at 6:15 AM, Lefty Leverenz <leftylever...@gmail.com> > wrote: > >> Agreed, the Hive wiki is woefully incomplete. But it does mention DROP >> for >> external tables in two sections of the DDL doc: >> >> - External Tables >> <https://cwiki.apache.org/confluence/display/Hive/LanguageM >> anual+DDL#LanguageManualDDL-ExternalTables>: >> "When dropping an EXTERNAL table, data in the table is NOT deleted >> from >> the file system." >> - Drop Table >> <https://cwiki.apache.org/confluence/display/Hive/LanguageM >> anual+DDL#LanguageManualDDL-DropTable>: >> "When dropping an EXTERNAL table, data in the table will NOT be >> deleted >> from the file system." >> >> A wiki page comparing managed and external tables would be very helpful, >> and the list is a good start. I suggest you open a JIRA issue. >> >> Who can help Lars with this task? >> >> -- Lefty >> >> >> On Thu, Jul 19, 2018 at 3:04 PM Lars Francke <lars.fran...@gmail.com> >> wrote: >> >> > Hi, >> > >> > I've been wondering if anyone can tell me what the differences and >> > limitations of managed vs. external tables are these days. >> > >> > I've seen the docs from Hortonworks[1] that list these features as not >> > supported by External tables: >> > * Query cache >> > * Materialized views, except in a limited way >> > * Default statistics gathering >> > * Compute queries using statistics >> > * Automatic runtime filtering >> > * File merging after insert >> > >> > But there are no details. For some of them I'm not even sure what they >> are >> > supposed to mean because I couldn't find any documentation in our Wiki >> :( >> > >> > So I'd love to create a Wiki page that describes the differences between >> > managed & external tables and list relevant JIRAs but I need your help >> for >> > that. >> > >> > I scanned the code for all references to TableType and this is the list >> I >> > found but I'm almost certainly missing something: >> > >> > * ARCHIVE/UNARCHIVE - DDLTask - Only works for managed tables >> > * TRUNCATE - DDLSemanticAnalyzer - Only works for managed tables >> > * MERGE/CONCATENATE - HiveRelOpMaterializationValidator - Only works >> for >> > managed tables >> > * Constraints - DDLSemanticAnalyzer - (NOT NULL, DEFAULT, CHECK, only >> RELY >> > ist allowed) >> > * IMPORT - ImportSemanticAnalyzer - This has some wild restrictions I >> > didn't follow for external tables >> > * Query Results Caching - https://issues.apache.org/jira >> /browse/HIVE-18513 >> > SemanticAnalyzer - Documentation missing for Results Cache >> > >> > So there's a bunch of those from the Hortonworks list missing. If anyone >> > could point me to documentation or code for those that'd be great. >> > >> > I also didn't find the most obvious/oldest one: Data is not deleted for >> > EXTERNAL tables on DROP, I'm sure I just missed it. >> > >> > And last but not least: I have not looked at the grammar to see what's >> > already forbidden at that level. >> > >> > As I said: Any hints would be greatly appreciated. >> > >> > Thank you! >> > >> > Lars >> > >> > A side note: There are so many fantastic features in Hive but because >> lots >> > of them are not or under-documented most people I know just stick to the >> > basics. That's a pity :( >> > >> > [1] < >> > >> > https://docs.hortonworks.com/HDPDocuments/HDP3/HDP-3.0.0/usi >> ng-hiveql/content/hive_hive_3_tables.html >> > > >> > >> > >
