[Bug] In version 1.3.3 of IoTDB, The trend calculation function DIFF does not correctly handle the non-ignore null-value attribute.

[LingweiKuang]

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• I searched in the issues and found nothing similar.

Version

version 1.3.3 (Build: ad95a7e)

Describe the bug and provide the minimal reproduce step

DROP DATABASE root.db0.t1
CREATE DATABASE root.db0.t1

CREATE TIMESERIES root.db0.t1.c0 WITH datatype=INT32;
INSERT INTO root.db0.t1(timestamp, c0) VALUES (1641024000000, 0), (1641024005000, null), (1641024010000, 2), (1641024015000, 3), (1641024020000, null);
CREATE TIMESERIES root.db0.t1.c1 WITH datatype=INT32;
INSERT INTO root.db0.t1(timestamp, c1) VALUES (1641024000000, 0), (1641024005000, 1), (1641024010000, 2), (1641024015000, 3), (1641024020000, 4);

# query 1
select DIFF(c0) from root.db0.t1;

# query 2
select DIFF(c0, 'ignoreNull'='false') from root.db0.t1;

What did you expect to see?

The expected result set for Query 1 is: null, 2, 1

The expected result set for Query 2 is: null, null, null, 1, null

What did you see instead?

The actual result set returned by Query 1 is: null, 2, 1

The actual result set returned by Query 2 is: null, 2, 1

Anything else?

Dear IoTDB team, In the above trend calculation function queries, Query 1 uses the DIFF function with the ignore null-value attribute enabled, while Query 2 has it disabled. However, the results returned by Query 2 indicate that null-value data was not included in the trend calculation, which does not meet expectations.

Are you willing to submit a PR?

• I'm willing to submit a PR!

[LingweiKuang]