## engines.delta_plans()


Ask Lean for the weighted delta plans of a Substrait JSON plan; the


Usage

``` python
engines.delta_plans(plan_json)
```


change to the view is the concatenation of their outputs.

Each delta plan reads the view's input tables `t` at their old contents and their changes as tables `t$delta`, which have the columns of `t` and an extra `__weight` column (+1 for an inserted row, -1 for a deleted one). Its output has the view's columns and a weight column likewise.


## Parameters


`plan_json: str`  
A Substrait plan as protobuf JSON, as [sverify.engines.substrait_json](engines.substrait_json.md#sverify.engines.substrait_json) or a node's [plan](Node.plan.md#sverify.Node.plan) write it.


## Returns


`list[str]`  
The delta plans, each a Substrait JSON plan in Lean's written form.


## Raises


`sverify.errors.NotIncremental`  
The plan has an operator without a verified delta rule.

`ValueError`  
The checker rejects the plan.