Bitmap functions¶
Bitmap functions work for two bitmaps Object value calculation, it is to return new bitmap or cardinality while using formula calculation, such as and, or, xor, and not, etc.
There are 2 kinds of construction methods for Bitmap Object. One is to be constructed by aggregation function groupBitmap with -State, the other is to be constructed by Array Object. It is also to convert Bitmap Object to Array Object.
RoaringBitmap is wrapped into a data structure while actual storage of Bitmap objects. When the cardinality is less than or equal to 32, it uses Set objet. When the cardinality is greater than 32, it uses RoaringBitmap object. That is why storage of low cardinality set is faster.
For more information on RoaringBitmap, see: CRoaring.
bitmapBuild¶
Build a bitmap from unsigned integer array.
bitmapBuild(array)
Parameters
array– unsigned integer array.
Example
SELECT bitmapBuild([1, 2, 3, 4, 5]) AS res
bitmapToArray¶
Convert bitmap to integer array.
bitmapToArray(bitmap)
Parameters
bitmap– bitmap object.
Example
SELECT bitmapToArray(bitmapBuild([1, 2, 3, 4, 5])) AS res
┌─res─────────┐ │ [1,2,3,4,5] │ └─────────────┘
bitmapAnd¶
Two bitmap and calculation, the result is a new bitmap.
bitmapAnd(bitmap,bitmap)
Parameters
bitmap– bitmap object.
Example
SELECT bitmapToArray(bitmapAnd(bitmapBuild([1,2,3]),bitmapBuild([3,4,5]))) AS res
┌─res─┐ │ [3] │ └─────┘
bitmapOr¶
Two bitmap or calculation, the result is a new bitmap.
bitmapOr(bitmap,bitmap)
Parameters
bitmap– bitmap object.
Example
SELECT bitmapToArray(bitmapOr(bitmapBuild([1,2,3]),bitmapBuild([3,4,5]))) AS res
┌─res─────────┐ │ [1,2,3,4,5] │ └─────────────┘
bitmapXor¶
Two bitmap xor calculation, the result is a new bitmap.
bitmapXor(bitmap,bitmap)
Parameters
bitmap– bitmap object.
Example
SELECT bitmapToArray(bitmapXor(bitmapBuild([1,2,3]),bitmapBuild([3,4,5]))) AS res
┌─res───────┐ │ [1,2,4,5] │ └───────────┘
bitmapAndnot¶
Two bitmap andnot calculation, the result is a new bitmap.
bitmapAndnot(bitmap,bitmap)
Parameters
bitmap– bitmap object.
Example
SELECT bitmapToArray(bitmapAndnot(bitmapBuild([1,2,3]),bitmapBuild([3,4,5]))) AS res
┌─res───┐ │ [1,2] │ └───────┘
bitmapCardinality¶
Retrun bitmap cardinality of type UInt64.
bitmapCardinality(bitmap)
Parameters
bitmap– bitmap object.
Example
SELECT bitmapCardinality(bitmapBuild([1, 2, 3, 4, 5])) AS res
┌─res─┐ │ 5 │ └─────┘
bitmapAndCardinality¶
Two bitmap and calculation, return cardinality of type UInt64.
bitmapAndCardinality(bitmap,bitmap)
Parameters
bitmap– bitmap object.
Example
SELECT bitmapAndCardinality(bitmapBuild([1,2,3]),bitmapBuild([3,4,5])) AS res;
┌─res─┐ │ 1 │ └─────┘
bitmapOrCardinality¶
Two bitmap or calculation, return cardinality of type UInt64.
bitmapOrCardinality(bitmap,bitmap)
Parameters
bitmap– bitmap object.
Example
SELECT bitmapOrCardinality(bitmapBuild([1,2,3]),bitmapBuild([3,4,5])) AS res;
┌─res─┐ │ 5 │ └─────┘
bitmapXorCardinality¶
Two bitmap xor calculation, return cardinality of type UInt64.
bitmapXorCardinality(bitmap,bitmap)
Parameters
bitmap– bitmap object.
Example
SELECT bitmapXorCardinality(bitmapBuild([1,2,3]),bitmapBuild([3,4,5])) AS res;
┌─res─┐ │ 4 │ └─────┘
bitmapAndnotCardinality¶
Two bitmap andnot calculation, return cardinality of type UInt64.
bitmapAndnotCardinality(bitmap,bitmap)
Parameters
bitmap– bitmap object.
Example
SELECT bitmapAndnotCardinality(bitmapBuild([1,2,3]),bitmapBuild([3,4,5])) AS res;
┌─res─┐ │ 2 │ └─────┘