Github user iyerr3 commented on a diff in the pull request:
https://github.com/apache/incubator-madlib/pull/54#discussion_r71961445
--- Diff: src/ports/postgres/modules/utilities/pivot.py_in ---
@@ -58,66 +61,255 @@ def pivot(schema_madlib, source_table, out_table,
pivoted table
@param aggregate_func The aggregate function to be applied to the
values
+ @param fill_value If specified, determines how to fill NULL
+ values resulting from pivot operation
+ @param keep_null The flag for determining how to handle NULL
+ values in pivot columns
"""
-
"""
Assume we have the following table
pivset( id INTEGER, piv FLOAT8, val FLOAT8 )
- where the piv column has 3 distinct values (10.0, 20.0 and 30.0).
+ where the piv column has 3 distinct values (10, 20 and 30).
If the pivot function call is :
SELECT madlib.pivot('pivset', 'pivout', 'id', 'piv', 'val');
We want to construct the following sql code to pivot the table.
CREATE TABLE pivout AS (SELECT id,
- sum(CASE WHEN "piv" = '10.0' THEN val ELSE NULL END ) as
"piv_10.0",
- sum(CASE WHEN "piv" = '20.0' THEN val ELSE NULL END ) as
"piv_20.0",
- sum(CASE WHEN "piv" = '30.0' THEN val ELSE NULL END ) as "piv_30.0"
+ avg(CASE WHEN "piv" = '10' THEN val ELSE NULL END ) as
"val_avg_piv_10",
+ avg(CASE WHEN "piv" = '20' THEN val ELSE NULL END ) as
"val_avg_piv_20",
+ avg(CASE WHEN "piv" = '30' THEN val ELSE NULL END ) as
"val_avg_piv_30"
FROM pivset GROUP BY id ORDER BY id)
"""
+
indices = split_quoted_delimited_str(index)
- pcol = split_quoted_delimited_str(pivot_cols)
- pval = split_quoted_delimited_str(pivot_values)
- validate_pivot_coding(source_table, out_table, indices, pcol, pval)
- new_col_names =[]
- sql_list = ["CREATE TABLE " + out_table + " AS (SELECT " + index]
+ pcols = split_quoted_delimited_str(pivot_cols)
+ pvals = split_quoted_delimited_str(pivot_values)
+ validate_pivot_coding(source_table, out_table, indices, pcols, pvals)
- pcol_no_quotes = strip_end_quotes(pcol[0].strip())
- pval_no_quotes = strip_end_quotes(pval[0].strip())
+ # Strip end quotes from pivot columns
+ pcols = [strip_end_quotes(pcol.strip()) for pcol in pcols]
+ pvals = [strip_end_quotes(pval.strip()) for pval in pvals]
+
+ # Parse the aggregate_func as a dictionary
+ try:
+ param_types = dict.fromkeys(pvals, list)
+ param_types['__madlib_def_pval__'] = list
+ agg_dict = extract_keyvalue_params(aggregate_func,param_types)
+ except KeyError, e:
+ with MinWarning("warning"):
+ plpy.warning("Pivot: Not all columns from '{aggregate_func}'"
+ " present in '{pivot_values}'".format(**locals()))
+ raise
+
+ # If the dictionary is empty, parse it as a list
+ agg_set = split_quoted_delimited_str(aggregate_func) if len(agg_dict)
< 1 \
+ else []
+ # If the list is empty set 'avg' as default
+ agg_dict['__madlib_def_agg__'] = ['avg'] if len(agg_set) < 1 else
agg_set
# Find the distinct values of pivot_cols
- distinct_values = plpy.execute(
- "SELECT array_agg(DISTINCT {pcol} ORDER BY {pcol}) AS value "
- "FROM {source_table}".
- format(pcol=pcol[0], source_table=source_table))
-
- distinct_values = [strip_end_quotes(item)
- for item in distinct_values[0]['value']]
- # The aggregate collects pivot_values values for a given pivot_cols
value
- case_str = ("{agg}("
- "CASE WHEN \"{{pcol}}\" = '{{value}}' THEN {pval} ELSE
NULL END"
- ")".
- format(agg=aggregate_func,
- pval=pval_no_quotes))
- sql_list.append(
- ", " +
- # Assign the name of the new column
- ', '.join("{case_str} as \"{{pcol}}_{{value}}\"".
- format(case_str=case_str).
- format(pcol=pcol_no_quotes, value=str(value))
- for value in distinct_values if value is not None))
+ # Note that the distinct values are appended in order of users list
+ # This ordering is important when we access pivot_comb entries
+ distinct_str = ["SELECT "]
+ distinct_str.append(
+ ', '.join("array_agg(DISTINCT {pcol}) AS {pcol}_values".
+ format(pcol=pcol) for pcol in pcols))
+ distinct_str.append(" FROM " + source_table)
+ distinct_values = plpy.execute(''.join(distinct_str))
+
+ # Collect the distinc values for every pivot column
--- End diff --
`s/distinc/distinct`
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