How do I Improve Pipe lining Queries

[krishnendu (Krishnendu Das)]

I am very very new to pipeline querying. I am trying to create sprint velocity chart where velocity = Total story points completed/ total story points planned for the current sprint.

I have calculated both the numerator and denominator but not able to use them in inside |math divide (a,b) where a and b comes from two expression .

in my code 'a' :
filters
| esdocs index="index_1*" fields="fields.StoryPoints, key, fields.status.statusCategory.name.keyword, fields.Sprints.endDate"
| filterrows fn={getCell "fields.status.statusCategory.name.keyword" | eq "Done"}
| filterrows fn={getCell "fields.Sprints.endDate" | gte value="date"}"
| math expression= "sum(fields.StoryPoints)"

and 'b' :
filters
| esdocs index="index_1*" fields="fields.StoryPoints, key, fields.status.statusCategory.name.keyword, fields.Sprints.endDate"
| filterrows fn={getCell "fields.Sprints.endDate" | gte value="date"}"
| math expression= "sum(fields.StoryPoints)"

--- Gauge Chart ----

filters
| esdocs index="index_1*" fields="fields.StoryPoints, key, fields.status.statusCategory.name.keyword, fields.Sprints.endDate"
| filterrows fn={getCell "fields.status.statusCategory.name.keyword" | eq "Done"}
| filterrows fn={getCell "fields.Sprints.endDate" | gte value="date"}"
| math expression= "sum(fields.StoryPoints)"
| progress shape="horizontalPill"
font={font size=24 family="'Open Sans', Helvetica, Arial, sans-serif" color="#000000" align="center"}
max= {filters
| esdocs index="index_1*" fields="fields.StoryPoints, key, fields.status.statusCategory.name.keyword, fields.Sprints.endDate"
| filterrows fn={getCell "fields.Sprints.endDate" | gte value="date"}"
| math expression= "sum(fields.StoryPoints)"
}
| render

Further can you please point to extensive examples and usage of piping . I have checked all from https://www.elastic.co/guide/en/kibana/master/canvas-function-reference.html. What language it supports ?

Further I am also not able to perform group by operations, subqueries through pipelines. Can anyone help me on that as well please.

P.S : I wont be using ESSQL.