I see. I think client side probably hold on to the iterators from the both sides and crawling forward to do the merge sort. in this case should be no much memory footprint either way where the filter is performed. On December 22, 2017 at 1:04:18 PM, James Taylor ([email protected]) wrote:
There’s no shipping of any tables with a sort merge join. On Fri, Dec 22, 2017 at 1:02 PM Ethan Wang <[email protected]> wrote: I see. Looks like it's possible the rhs (MYTABLE) is too big to ship around without get filtered first. Just for experiment, if you took out hint USE_SORT_MERGE_JOIN, what will be the plan? On December 22, 2017 at 12:46:25 PM, James Taylor ([email protected]) wrote: For sort merge join, both post-filtered table results are sorted on the server side and then a merge sort is done on the client-side. On Fri, Dec 22, 2017 at 12:44 PM, Ethan <[email protected]> wrote: Hello Flavio, From the plan looks like to me the second query is doing the filter at parent table (PEOPLE). So what is the size of your PEOPLE and MYTABLE (after filtered) respectively? For sort merge join, anyone knows are the both sides get shipped to client to do the merge sort? Thanks, On December 22, 2017 at 9:58:30 AM, Flavio Pompermaier ([email protected]) wrote: Any help here...? On 20 Dec 2017 17:58, "Flavio Pompermaier" <[email protected]> wrote: Hi to all, I'm trying to find the best query for my use case but I found that one version work and the other one does not (unless that I don't apply some tuning to timeouts etc like explained in [1]). The 2 queries extract the same data but, while the first query terminates the second does not. PS: without the USE_SORT_MERGE_JOIN both queries weren't working SELECT /*+ USE_SORT_MERGE_JOIN */ COUNT(*) FROM PEOPLE ds JOIN MYTABLE l ON ds.PERSON_ID = l.LOCALID WHERE l.EID IS NULL AND l.DSID = 'PEOPLE' AND l.HAS_CANDIDATES = FALSE; +---------------------------------------------------------------------------------------------------------------+-----------------+----------------+----------------+ | PLAN | EST_BYTES_READ | EST_ROWS_READ | EST_INFO_TS | +---------------------------------------------------------------------------------------------------------------+-----------------+----------------+----------------+ | SORT-MERGE-JOIN (INNER) TABLES | 14155777900 | 12077867 | 1513754378759 | | CLIENT 42-CHUNK 6168903 ROWS 11324622221 BYTES PARALLEL 3-WAY FULL SCAN OVER PEOPLE | 14155777900 | 12077867 | 1513754378759 | | SERVER FILTER BY FIRST KEY ONLY | 14155777900 | 12077867 | 1513754378759 | | CLIENT MERGE SORT | 14155777900 | 12077867 | 1513754378759 | | AND (SKIP MERGE) | 14155777900 | 12077867 | 1513754378759 | | CLIENT 15-CHUNK 5908964 ROWS 2831155679 BYTES PARALLEL 15-WAY RANGE SCAN OVER MYTABLE [0] - [2] | 14155777900 | 12077867 | 1513754378759 | | SERVER FILTER BY (EID IS NULL AND DSID = 'PEOPLE' AND HAS_CANDIDATES = false) | 14155777900 | 12077867 | 1513754378759 | | SERVER SORTED BY [L.LOCALID] | 14155777900 | 12077867 | 1513754378759 | | CLIENT MERGE SORT | 14155777900 | 12077867 | 1513754378759 | | CLIENT AGGREGATE INTO SINGLE ROW | 14155777900 | 12077867 | 1513754378759 | +---------------------------------------------------------------------------------------------------------------+-----------------+----------------+----------------+ SELECT /*+ USE_SORT_MERGE_JOIN */ COUNT(*) FROM (SELECT LOCALID FROM MYTABLE WHERE EID IS NULL AND DSID = 'PEOPLE' AND HAS_CANDIDATES = FALSE) l JOIN PEOPLE ds ON ds.PERSON_ID = l.LOCALID; +--------------------------------------------------------------------------------------------------------------+-----------------+----------------+----------------+ | PLAN | EST_BYTES_READ | EST_ROWS_READ | EST_INFO_TS | +--------------------------------------------------------------------------------------------------------------+-----------------+----------------+----------------+ | SORT-MERGE-JOIN (INNER) TABLES | 14155777900 | 12077867 | 1513754378759 | | CLIENT 15-CHUNK 5908964 ROWS 2831155679 BYTES PARALLEL 3-WAY RANGE SCAN OVER MYTABLE [0] - [2] | 14155777900 | 12077867 | 1513754378759 | | SERVER FILTER BY (EID IS NULL AND DSID = 'PEOPLE' AND HAS_CANDIDATES = false) | 14155777900 | 12077867 | 1513754378759 | | CLIENT MERGE SORT | 14155777900 | 12077867 | 1513754378759 | | AND (SKIP MERGE) | 14155777900 | 12077867 | 1513754378759 | | CLIENT 42-CHUNK 6168903 ROWS 11324622221 BYTES PARALLEL 42-WAY FULL SCAN OVER PEOPLE | 14155777900 | 12077867 | 1513754378759 | | SERVER FILTER BY FIRST KEY ONLY | 14155777900 | 12077867 | 1513754378759 | | SERVER SORTED BY [DS.PERSON_ID] | 14155777900 | 12077867 | 1513754378759 | | CLIENT MERGE SORT | 14155777900 | 12077867 | 1513754378759 | | CLIENT AGGREGATE INTO SINGLE ROW | 14155777900 | 12077867 | 1513754378759 | +--------------------------------------------------------------------------------------------------------------+-----------------+----------------+----------------+ 10 rows selected (0.041 seconds) What do you think? Whould I try to give more resources to HBase/Phoenix or is the first query the best (and reliable) one? Any insight about this is highly appreciated.. Best, Flavio
