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https://issues.apache.org/jira/browse/MADLIB-908?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15425626#comment-15425626
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Rahul Iyer commented on MADLIB-908:
-----------------------------------
Current behavior is that pivot only works with agg functions that ignore NULL
values (i.e. transition function is STRICT).
Use the following and you'll get the intended answer.
{code}
CREATE FUNCTION array_add1(ANYARRAY, ANYELEMENT) RETURNS ANYARRAY AS $$
SELECT $1 || $2
$$ LANGUAGE sql STRICT;
CREATE AGGREGATE array_accum1 (anyelement) (
sfunc = array_add1,
stype = anyarray,
initcond = '{}'
);
DROP TABLE IF EXISTS pivout;
SELECT madlib.pivot('pivset_ext', 'pivout', 'id', 'piv', 'val', 'array_accum1');
SELECT * FROM pivout ORDER BY id;
{code}
> Pivoting - Phase 1 (basic pivot)
> --------------------------------
>
> Key: MADLIB-908
> URL: https://issues.apache.org/jira/browse/MADLIB-908
> Project: Apache MADlib
> Issue Type: New Feature
> Components: Module: Utilities
> Reporter: Frank McQuillan
> Fix For: v1.9.1
>
>
> Story
> As a data scientist, I want to perform *basic* pivot operation on my data, so
> that I can prepare it for input to predictive analytics algorithms.
> Details
> Basic pivot for this story means:
> * single index column
> * single pivot column
> * single value column
> * single aggregate function = SUM
> * no fill value
> PDL Tools [5] supports some of this functionality but its interface is
> confusing. Pandas [2], PostgreSQL [4] and Aster [6] also have some version
> of pivoting that we can learn from.
> In general, we are following Pandas ideas.
> References
> [1] Pivot table general information, like what is pivoting?
> https://en.wikipedia.org/wiki/Pivot_table
> [2] Pandas pivot tables and cross-tabulations
> http://pandas.pydata.org/pandas-docs/stable/reshaping.html#pivot-tables-and-cross-tabulations
> http://pandas.pydata.org/pandas-docs/stable/cookbook.html#cookbook-pivot
> http://pbpython.com/pandas-pivot-table-explained.html
> [3] GPDB pivot_sum function
> http://gpdb.docs.pivotal.io/4320/admin_guide/query.html#topic30
> [4] PostgreSQL tablefunc
> http://www.postgresql.org/docs/9.4/static/tablefunc.html
> [5] PDL tools pivoting routines
> http://pdl-tools.pa.pivotal.io/group__grp__pivot.html
> http://pdl-tools.pa.pivotal.io/group__grp__pivot01.html
> [6] Aster Pivot and Unpivot functions
> User Guide
> http://www.info.teradata.com/eDownload.cfm?itemid=122580002
> [7] PostgreSQL aggregates
> http://www.postgresql.org/docs/8.2/static/functions-aggregate.html
> [8] PostgreSQL basic statements/assignment operator,
> http://www.postgresql.org/docs/8.2/static/plpgsql-statements.html
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