Add support open command

[jiashenC]

Currently support open jpeg image and return a numpy array for it.

[gaurav274]

How will we use it in a query?

[jiashenC]

How will we use it in a query?

@gaurav274 I think it can be just embedded in any statement that needs to get a numpy array from the source image (as we discussed here #478).

SELECT id, data FROM table WHERE similarity(OPEN('../path/to/img.jpg'), data, FeatureExtractor) TOP 5;

[gaurav274]

Yes, how will the query execution plan look like for this example? Since open is an operator and similarity will be part of an expression. We might have to implement open as an expression. What do you think? @xzdandy

[xzdandy]

My assumption is that '../path/to/img.jpg' locates on the client side (i.e., not server, otherwise we will use the load command to load the image?)
Than this logic should be at the client library where, for example, we turn this image into a base64 encoded string and the expression at the server side decodes it.

[gaurav274]

My assumption is that '../path/to/img.jpg' locates on the client side (i.e., not server, otherwise we will use the load command to load the image?) Than this logic should be at the client library where, for example, we turn this image into a base64 encoded string and the expression at the server side decodes it.

We assume it is on the server side and the user does not want to use an existing file. In theory, we can replace open with a select query but not for now.

[jiashenC]

Decide to implement open as functional expression after discussion.