Use `min_value` and `max_value` on statistics to avoid `ExecutionPlan.execute`

[samuelcolvin]

Describe the bug

Maybe related to #5535, but I couldn't find anything identical, so created a fresh issue.

If this is a known bug and you think the fix might be moderate in scope, I'm happy to have a go at fixing it?

To Reproduce

I have a custom TableProvider and ExecutionPlan, where calling execute is somewhat expensive and I want to avoid calling it if no data will match.

The execution plan can return helpful statistics from .statistics(), including for example, for one column:

...
ColumnStatistics {
    null_count: Precision::Exact(0),
    max_value: Precision::Exact(ScalarValue::Int64(Some(4))),
    min_value: Precision::Exact(ScalarValue::Int64(Some(4))),
    distinct_count: Precision::Exact(1),
},

E.g. "in this column all values are equal to 4". This is successfully used by Datafusion if I query value is null, the execute() function is never alled.

But if I query value > 5 or value < 0, the statistic is ignored and execute() is still called.

Expected behavior

min_value and max_value of ColumnStatistics should be used for pruning and the query plan should not require the "slow" execute method to be called.

Additional context

I can give a fairly minimal example if required, but I thought best to report the issue and check if it was well known before going to that effort?

I've tried this on both main (as of today) and 37.1.0

[samuelcolvin]

For anyone else looking for this, the solution is to implement supports_filters_pushdown on the table, then use that to apply filters within scan.

Feel free to close this if you like.

[alamb]

I think using the reported statistics to prune using datafusion::physical_optimizer::pruning::PruningPredicate would be a nice improvement (so each table provider didn't have to apply the basic min/max filters themselves)

[alamb]

Relabed from bug to feature -- thanks @samuelcolvin

[samuelcolvin]

@alamb using PruningPredicate makes sense, but please can you point me at where I need to make changes to add this functionality?

[alamb]

@alamb using PruningPredicate makes sense, but please can you point me at where I need to make changes to add this functionality?

I recommend updating the existing though poorly named AggregateStatistics pass

And there you could potentially call ExecutionPlan::statistics() and use PruningPredicate to prove that some predicates can't be true and replace them with PlaceholderRowExec

[alamb]

(Thank you for working on this, bTW)

[edmondop]

@samuelcolvin have you already started to write code?

[samuelcolvin]

No code yet, if you'd like to work on this, feel free.

[samuelcolvin]

Actually I'm on a flight today, so might have some time to work on this.