I think flatten is functioning as designed, but perhaps we need to treat this case differently. It might make sense to return a single row with a null for the flattened column in this case. The only model for "flatten" that I know of is google Big Query. We should see how they handle this case.
On Tue, Feb 3, 2015 at 12:27 PM, MapR <[email protected]> wrote: > In a table, column with null values we > present as nulls or empty values with other columns. I never had an > experience with c1, c2, c3 (columns ) not presented when c3 has null values > even though c1, c2 have notnull values. > > Sudhakar Thota > Sent from my iPhone > > > On Feb 3, 2015, at 11:57 AM, Andries Engelbrecht < > [email protected]> wrote: > > > > In listing 3 it looks like flatten is doing the correct thing by > representing each element in the array with a new row and the element in > the column output. > > And also for arrays that are empty there is no output row. > > > > —Andries > > > >> On Feb 3, 2015, at 11:54 AM, Sudhakar Thota <[email protected]> > wrote: > >> > >> It will be more appropriate if I add my file to have data to facilitate > quick test. > >> > >> [root@maprdemo clicks]# cat sthota_test_1.json > >> {"a":"r1cl1", "b":"r1c2","c":{ "x" : 1, "y" : "a string", "z" : [ 1] }} > >> {"a":"r2cl1", "b":"r2c2","c":{ "x" : 2, "y" : "a string", "z" : [ 1,2] > }} > >> {"a":"r3cl1", "b":"r3c2","c":{ "x" : 3, "y" : "a string", "z" : [ > 1,2,3] }} > >> {"a":"r4cl1", "b":"r4c2","c":{ "x" : 4, "y" : "a string", "z" : [ > 1,2,3,4] }} > >> {"a":"r5cl1", "b":"r5c2","c":{ "x" : 5, "y" : "a string", "z" : [ > 1,2,3,4,5] }} > >> {"a":"r6cl1", "b":"r6c2","c":{ "x" : 6, "y" : "a string" }} > >> > >> > >> Begin forwarded message: > >> > >>> From: Sudhakar Thota <[email protected]> > >>> Subject: Drill - Flatten function - help please > >>> Date: February 3, 2015 at 11:52:39 AM PST > >>> To: [email protected] > >>> > >>> Hi Drillers, > >>> > >>> I have a request here about flatten function. I want to know if this > is an expected behavior of drill flatten function with json documents. > >>> > >>> Listing-1 is contents of my json collection where I have intentionally > included a empty array. > >>> Listing-2 shows that if I don’t call flatten function it shows all > records. > >>> Listing-3 shows that if I call flatten function, row6 (r6cl1…) is > ignored. I am using that in my projections not in predicate, but it looks > like treated as predicate. > >>> > >>> Please correct me if I am wrong and let me know if there is any work > around. > >>> > >>> Listing:1 > >>> > >>> 0: jdbc:drill:> SELECT t.a,t.b,t.c.x, t.c.y, t.c.z from > dfs.`/data/nested/clicks/sthota_test_1.json` as t; > >>> +------------+------------+------------+------------+------------+ > >>> | a | b | EXPR$2 | EXPR$3 | EXPR$4 | > >>> +------------+------------+------------+------------+------------+ > >>> | r1cl1 | r1c2 | 1 | a string | ["1"] | > >>> | r2cl1 | r2c2 | 2 | a string | ["1","2"] | > >>> | r3cl1 | r3c2 | 3 | a string | ["1","2","3"] | > >>> | r4cl1 | r4c2 | 4 | a string | > ["1","2","3","4"] | > >>> | r5cl1 | r5c2 | 5 | a string | > ["1","2","3","4","5"] | > >>> | r6cl1 | r6c2 | 6 | a string | [] | > >>> +------------+------------+------------+------------+------------+ > >>> 6 rows selected (0.125 seconds) > >>> 0: jdbc:drill:> > >>> > >>> Listing:2 > >>> > >>> 0: jdbc:drill:> SELECT t.a,t.b,t.c.x, t.c.y from > dfs.`/data/nested/clicks/sthota_test_1.json` as t; > >>> +------------+------------+------------+------------+ > >>> | a | b | EXPR$2 | EXPR$3 | > >>> +------------+------------+------------+------------+ > >>> | r1cl1 | r1c2 | 1 | a string | > >>> | r2cl1 | r2c2 | 2 | a string | > >>> | r3cl1 | r3c2 | 3 | a string | > >>> | r4cl1 | r4c2 | 4 | a string | > >>> | r5cl1 | r5c2 | 5 | a string | > >>> | r6cl1 | r6c2 | 6 | a string | > >>> +------------+------------+------------+------------+ > >>> 6 rows selected (0.163 seconds) > >>> > >>> Listing:3 > >>> > >>> 0: jdbc:drill:> SELECT t.a,t.b,t.c.x, t.c.y, flatten(t.c.z) from > dfs.`/data/nested/clicks/sthota_test_1.json` as t; > >>> +------------+------------+------------+------------+------------+ > >>> | a | b | EXPR$2 | EXPR$3 | EXPR$4 | > >>> +------------+------------+------------+------------+------------+ > >>> | r1cl1 | r1c2 | 1 | a string | 1 | > >>> | r2cl1 | r2c2 | 2 | a string | 1 | > >>> | r2cl1 | r2c2 | 2 | a string | 2 | > >>> | r3cl1 | r3c2 | 3 | a string | 1 | > >>> | r3cl1 | r3c2 | 3 | a string | 2 | > >>> | r3cl1 | r3c2 | 3 | a string | 3 | > >>> | r4cl1 | r4c2 | 4 | a string | 1 | > >>> | r4cl1 | r4c2 | 4 | a string | 2 | > >>> | r4cl1 | r4c2 | 4 | a string | 3 | > >>> | r4cl1 | r4c2 | 4 | a string | 4 | > >>> | r5cl1 | r5c2 | 5 | a string | 1 | > >>> | r5cl1 | r5c2 | 5 | a string | 2 | > >>> | r5cl1 | r5c2 | 5 | a string | 3 | > >>> | r5cl1 | r5c2 | 5 | a string | 4 | > >>> | r5cl1 | r5c2 | 5 | a string | 5 | > >>> +------------+------------+------------+------------+------------+ > >>> 15 rows selected (0.171 seconds) > >>> > >>> Thanks > >>> Sudhakar Thota > > > -- Steven Phillips Software Engineer mapr.com
