Conversion from pyarrow Expressions to QueryBuilder expressions
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IvoDD
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alexowens90,
willdealtry and
poodlewars
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Introduces `ExpressionNode.from_pyarrow_expression_str`.
This is required for predicate pushdown integration with polars. E.g.
when we do:
```
lf = polars.scan_arcticdb(arctic_identifier)
lf = lf.filter(pl.col("float_col") <= 40.1)
lf.collect()
```
When calling `collect` the filter will get pushed down to our (to be
implemented) `polars.scan_arcticdb` via a callback. The filter is given
as a string which can be evaluated to a pyarrow expression. For
reference string construction happens [here](https://github.com/pola-rs/polars/blob/4e286d8c83b0fcb56f0a7ea06d2eb731f179e01e/crates/polars-plan/src/plans/python/pyarrow.rs#L25).
I've decided to keep this conversion code in core arcticdb instead of
polars for a few reasons:
- Gives us more flexibility if we decide to update our `QueryBuilder`
expressions
- We'll have less code to maintain in a repository which is not ours
- Automated tests allow us to not accidentally break polars predicate
pushdown to arcticdb
For additional reference see how pyiceberg handles predicate pushdown
from polars [here](https://github.com/pola-rs/polars/blob/4e286d8c83b0fcb56f0a7ea06d2eb731f179e01e/py-polars/polars/io/iceberg.py#L197-L200)
And how this might fit in the prototype `polars.scan_arcticdb`
implementation [here](https://github.com/IvoDD/polars/pull/1/files)
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alexowens90
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| if isinstance(a.op, ast.USub): | ||
| # pyarrow expressions don't support unary subrtract, so this branch will not be reached. | ||
| # Leaving as future-proofing in case they ever introduce it. | ||
| return -operand |
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Reference Issues/PRs
Monday ref: 8471524478
What does this implement or fix?
Introduces
ExpressionNode.from_pyarrow_expression_str.This is required for predicate pushdown integration with polars. E.g. when we do:
When calling
collectthe filter will get pushed down to our (to be implemented)polars.scan_arcticdbvia a callback. The filter is given as a string which can be evaluated to a pyarrow expression. For reference string construction happens here.I've decided to keep this conversion code in core arcticdb instead of polars for a few reasons:
QueryBuilderexpressionsFor additional reference see how pyiceberg handles predicate pushdown from polars here
And how this might fit in the prototype
polars.scan_arcticdbimplementation hereChange Type (Required)
Any other comments?
Checklist
Checklist for code changes...