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Incorrect result when groupby is applied to a view #1542

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st-pasha opened this issue Jan 13, 2019 · 0 comments · Fixed by #1545
Closed

Incorrect result when groupby is applied to a view #1542

st-pasha opened this issue Jan 13, 2019 · 0 comments · Fixed by #1545
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@st-pasha
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bug Any bugs / errors in datatable; however for severe bugs use [segfault] label DT[i，j，...] Issues related to evaluation of the primary expression `DT[i, j, ...]` groupby Group-by functionality and Reducers views Issues that are specific to "view" frames only
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Release 0.8.0

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@st-pasha
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>>> from datatable import *
>>> DT = Frame(a=[1,2,3,1,2,3], b=[3,6,2,4,3,1], c=list("bdbbdb"))
>>> DT[f.a != 1, :]
      a   b  c 
---  --  --  --
 0    2   6  d 
 1    3   2  b 
 2    2   3  d 
 3    3   1  b 

[4 rows x 3 columns]

>>> DT[f.a != 1, :][:, max(f.b), by(f.c)]
     c   C0
---  --  --
 0   d    3
 1   b    3

[2 rows x 2 columns]
@st-pasha st-pasha added bug Any bugs / errors in datatable; however for severe bugs use [segfault] label views Issues that are specific to "view" frames only groupby Group-by functionality and Reducers DT[i，j，...] Issues related to evaluation of the primary expression `DT[i, j, ...]` labels Jan 13, 2019
@st-pasha st-pasha added this to the Release 0.8.0 milestone Jan 13, 2019
@st-pasha st-pasha self-assigned this Jan 13, 2019
@st-pasha st-pasha mentioned this issue Jan 14, 2019
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st-pasha added a commit that referenced this issue Jan 14, 2019
@st-pasha
Fix groupby when applied to a view (#1545)
0e20f4e 
Added new internal method `DataTable::group(spec, as_view) -> pair<RowIndex, Groupby>`, as a replacement for `DataTable::sortby()`. The new method has more predictable return value: the returned rowindex either applies to the column, or to its source (for a view column), depending on the value of the parameter `as_view`.

Closes #1542
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@st-pasha st-pasha

Labels
bug Any bugs / errors in datatable; however for severe bugs use [segfault] label DT[i，j，...] Issues related to evaluation of the primary expression `DT[i, j, ...]` groupby Group-by functionality and Reducers views Issues that are specific to "view" frames only
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Release 0.8.0
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Fix groupby when applied to a view h2oai/datatable
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@st-pasha