Pcount - ObjectVision/GeoDMS GitHub Wiki

Aggregation functions pcount

• pcount(a)
• pcount_uint8(a), pcount_uint16(a), pcount_uint32(a), pcount_uint64(a)

pcount is short for partition count, and is used to obtain a count for each possible value of a relational attribute, i.e. an attribute with values than is or can be the domain of other attributes.

The domain of the results of these functions is set to the values unit of the argument a.

• pcount(a) is defined as the count of the number of entries of a relation in the related domain unit. The values type is the cardinality type of the values of the domain of a:
  • Int8, UInt8 -> UInt8;
  • Int16, UInt16 -> UInt16;
  • Int32, UInt32, SPoint, WPoint -> UInt32;
  • Int64, UInt64, IPoint, UPoint -> UInt64.
• pcount_uint(8|16|32|64)(a) are pcount variants resulting in uint8, uint16, uint32, or uint64 data items respectively, which saves memory when one knows that the number of occurrences of each value of a does not exceed the maximum number of the specified values type.

Use the has_any (a) function if only the occurence of values is required.

• attribute a with uint2, uint4, uint8, uint16, uint32, uint64, spoint, wpoint, ipoint, upoint or bool value type

attribute<uint32> pcountReg (Region) := pcount(City/Region_rel);

domain City, nr of rows = 7

domain Region, nr of rows = 5

• count
• has_any