ddlReduce() - remove duplicate records from a collection
ddlReduce() - remove duplicate records from a
collection
Prototype:
void ddlReduce(
CONTROL *ctl,
char *OptnStr,
char *ArgList);
Permitted values in OptnStr:
/S - use the sorted collection as input
Form of ArgList:
<cx> [<dgname>]
<field-name1> [<field-name2>] ...
Description:
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Remove duplicate records from the source collection based on the
concatenated value, called the reduce-key:
<field-name1> [<field-name2>] ...
For each unique reduce-key, the first occurring instance in the
source collection is preserved; all subsequent instances are removed
from the collection.
When the /S option is used, for each unique reduce-key, the first occurring instance in the sorted
collection is preserved; all subsequent instances are removed
from the collection.
After the reduce function is completed, the sorted collection is
closed, and the reduced native collection remains.
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Notes:
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1) ddlSort() with the /R option is functionally
equivalent to ddlReduce().
In this case, the combined sort-key is also the reduce-key.
Duplicate records are removed from both the sorted collection and the raw collection.
Records that occur first in the sorted order are the surviving records.
Duplicate records that occur later in the sorted order are removed.
After the sort function is completed, the sorted collection remains.
To access the reduced raw collection, use ddlClear()
with the /S option.
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Values returned in Control Structure:
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| Control.Ans1 |
Total number of records remaining in the source collection. |
| Control.Ans2 |
Total number of records in the source collection. |
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