## Proposed changes
https://github.com/apache/doris/pull/38945
Added the computeSignature function for millisecond/microsecond
calculation functions to generate parameters and return values with the
appropriate precision.
Modified the microSecondsAdd function, which was used for constant
folding, because constant folding uses the precision of the parameters
for calculation. However, for millisecond/microsecond calculations, it
is necessary to set the precision to the maximum to ensure correct
display.
before
```
mysql> SELECT MICROSECONDS_SUB('2010-11-30 23:50:50', 2);
+-------------------------------------------------------------------+
| microseconds_sub(cast('2010-11-30 23:50:50' as DATETIMEV2(0)), 2) |
+-------------------------------------------------------------------+
| 2010-11-30 23:50:49 |
+-------------------------------------------------------------------+
```
now
```
mysql> SELECT MICROSECONDS_SUB('2010-11-30 23:50:50', 2);
+-------------------------------------------------------------------+
| microseconds_sub(cast('2010-11-30 23:50:50' as DATETIMEV2(0)), 2) |
+-------------------------------------------------------------------+
| 2010-11-30 23:50:49.999998 |
+-------------------------------------------------------------------+
```
<!--Describe your changes.-->
## Proposed changes
Issue Number: close #xxx
<!--Describe your changes.-->
ebf5d70c9d