4.7 KiB
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 │
└─────┘