feat: Add symlinks to data files instead of copying

[suryatejreddy]

This PR adds a major change (with little code).

Current Behavior

We copy the dataset file that the user loads into the eva_datasets folder.

Change

This PR modifies this behavior to add a symlink from eva_datasets to the file on the user's filesystem. In case the user later deletes the file, an appropriate error is thrown.

Testing

• Added test cases for individual and multiple file loads.
• Added test case for testing correct exception thrown if the file is removed from user's system.

[gaurav274]

Can you verify this also fixes #563? Thanks!

[suryatejreddy]

@gaurav274 This doesn't throw an error while trying to load a missing file. But it throws the dataset missing file exception when we try to run a SELECT on a missing file.

file_name = "dog.png"
cursor.execute('LOAD IMAGE "' + file_name + '" INTO MyImages;')
response = cursor.fetch_all()
print(response)
>>>
@status: ResponseStatus.SUCCESS
@batch: 
                            0
0  Number of loaded IMAGE: 0
@query_time: 0.04345816600000063

cursor.execute("""SELECT data
                FROM MyImages""")
response = cursor.fetch_all()
print(response)
>>>
@status: ResponseStatus.FAIL
@batch: 
 None
@error: Dataset file not found. Please check the files still exists at the original path.

I can maybe add a similar exception when you load a missing file.

[gaurav274]

Okay, so it does say 0 files loaded. We can discuss, what the behavior should be if some files are missing while loading and selecting. Btw, in this case if no file was loaded, why does it say missing file? Shouldn't it just execute with empty output?

[suryatejreddy]

Okay, so it does say 0 files loaded. We can discuss, what the behavior should be if some files are missing while loading and selecting. Btw, in this case if no file was loaded, why does it say missing file? Shouldn't it just execute with empty output?

It says missing file during select because the original dataset file doesn't exist. That is the check that I have implemented as of now. I think if files are missing while loading we should raise an immediate error there.

[gaurav274]

Can we merge this PR, or is there anything remaining?