Way to check if Delta table exists at specified path

[jorritsandbrink]

Description

It would be nice to have a way to check if a Delta table exists at a given path.

Delta Spark has the DeltaTable.isDeltaTable() method: https://docs.delta.io/latest/api/python/spark/index.html#delta.tables.DeltaTable.isDeltaTable

Use Case
When merging into a Delta table, you first define a DeltaTable object before calling merge on it:

dt = DeltaTable("path_to_table_that_may_not_exist_yet")

dt.merge(...)

This fails with a TableNotFoundError if the table does not exist.

Having the isDeltaTable method (or similar) would enable this flow:

if DeltaTable.isDeltaTable("path_to_table_that_may_not_exist_yet"):
    dt = DeltaTable("path_to_table_that_may_not_exist_yet")
    dt.merge(...)
else:
    write_deltalake(...)

The above requires two path lookups, which adds unnecessary latency.

Alternatively, something like this could be nice:

dt = DeltaTable("path_to_table_that_may_not_exist_yet", return_none_if_not_exists=True)

if dt is not None:
    dt.merge(...)
else:
    write_deltalake(...)

[omkar-foss]

Hey @jorritsandbrink, so there's a function called try_get_deltatable() in the code here that provides this functionality.

try_get_deltatable() returns None if the table is not found at the specified path (i.e. TableNotFoundError occurs), otherwise it returns the DeltaTable instance already existing at the specified path. It can be used with your above mentioned flow as follows:

from deltalake.writer import try_get_deltatable

dt = try_get_deltatable("path_to_table_that_may_not_exist_yet")
if dt is not None:
    dt.merge(...)
else:
    write_deltalake(...)

And yes I agree with you, since this is a very common use case, we can consider abstracting it to something more meaningful like DeltaTable.isDeltaTable().

Until then, I suppose we should also consider adding the try_get_deltatable() function to the delta-rs documentation, may help other users looking for this functionality.

[jorritsandbrink]

@omkar-foss thanks! I'll use try_get_deltatable().

[ion-elgreco]

Feel free to open a PR for a static method is_deltatable()

[omkar-foss]

take

[omkar-foss]

Feel free to open a PR for a static method is_deltatable()

Hey @ion-elgreco @jorritsandbrink hope you both are doing great. I've opened PR #2715, please have a look whenever you get a chance. Thanks!