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TDIGEST.MERGE

Syntax
TDIGEST.MERGE destination-key numkeys source-key [source-key ...]
  [COMPRESSION compression] [OVERRIDE]
Available in:
Redis Open Source / Bloom 2.4.0
Time complexity:
O(N*K), where N is the number of centroids and K being the number of input sketches
ACL categories:
@tdigest, @write, @slow,
Compatibility:
Redis Enterprise and Redis Cloud compatibility

Merges multiple t-digest sketches into a single sketch.

Required arguments

destination-key

is the key name for a t-digest sketch to merge observation values to.

If destination-key does not exist, a new sketch is created.

If destination-key is an existing sketch, its values are merged with the values of the source keys. To override the destination key contents use OVERRIDE.

numkeys

the number of sketches from which to merge observation values (one or more).

source-key

Each source-key is a key name for a t-digest sketch from which to merge observation values.

Optional arguments

COMPRESSION compression

is a controllable tradeoff between accuracy and memory consumption. 100 is a common value for normal uses and also the default if not specified. 1000 is more accurate. For more information on scaling of accuracy versus the compression value see The t-digest: Efficient estimates of distributions.

When COMPRESSION is not specified:

  • If destination-key does not exist or if OVERRIDE is specified, the compression is set to the maximum value among all source sketches.
  • If destination-key already exists and OVERRIDE is not specified, its compression is not changed.
OVERRIDE

If destination-key already exists and OVERRIDE is specified, the key is overwritten.

Examples 

redis> TDIGEST.CREATE s1
OK
redis> TDIGEST.CREATE s2
OK
redis> TDIGEST.ADD s1 10.0 20.0
OK
redis> TDIGEST.ADD s2 30.0 40.0
OK
redis> TDIGEST.MERGE sM 2 s1 s2
OK
redis> TDIGEST.BYRANK sM 0 1 2 3 4
1) "10"
2) "20"
3) "30"
4) "40"
5) "inf"

Redis Enterprise and Redis Cloud compatibility

Redis
Enterprise		 Redis
Cloud		 Notes
✅ Supported
 ✅ Flexible & Annual
✅ Free & Fixed

Return information

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