[CALCITE-2209] Support loading model file through URL

[walterddr]

This addresses: https://issues.apache.org/jira/browse/CALCITE-2209

[suez1224]

Can we fix the test errors?

[walterddr]

@suez1224 I pushed a fix on all the test errors regarding the upgrade from File based to URI based in all SchemaFactory/TableFactory. I am not sure whether this is categorized as backward incompatible change or not. Please take a look.

[AsmaZgo]

thank you for addressing this feature! it will improve the quality of my tool.

[vlsi]

@walterddr , this looks like a backward-incompatible change. In other words, clients have to update their code even though they don't use URIs yet.

Have you though of a possibility to keep previous code intact while allowing to leverage new API if required?

[walterddr]

hmm. this was confusing to me. I was not sure about the original implementation to directly convert the Object to File.

How about:

Object baseDirObj = operand.get(ModelHandler.ExtraOperand.BASE_DIRECTORY.camelName);
Final File base;
if (baseDirObj instanceof URI) {
  uri = (URI) baseDirObj;
  base = new File(uri);
} else if (baseDirObj instanceof File) {
  base = (File) baseDirObj;
} else {
  throw IllegalArgumentException(...);
}

[walterddr]

Thanks for the feedback @vlsi . sorry for the late reply, I just replied with a possible solution, please kindly take a look and see if I am heading the right direction.

[walterddr]

hmm. this was confusing to me. I was not sure about the original implementation to directly convert the Object to File.

How about:

Object baseDirObj = operand.get(ModelHandler.ExtraOperand.BASE_DIRECTORY.camelName);
Final File base;
if (baseDirObj instanceof URI) {
  uri = (URI) baseDirObj;
  base = new File(uri);
} else if (baseDirObj instanceof File) {
  base = (File) baseDirObj;
} else {
  throw IllegalArgumentException(...);
}

[walterddr]

@vlsi one more comment on this is that I changed this to always use URI as Object type in the operandMap. I am assuming this is also a backward-incompatible change since other users who directly alter the operandMap will also have to change File type to URI type.

Any suggestions on how to make it backward compatible. My initial thought would be to give another key, say:

case BASE_DIRECTORY:
  // ...
case BASE_DIRECTORY_URI:
  // ... 

and mark BASE_DIRECTORY as deprecated key

[nemccarthy]

Shame this didnt make it in. We could really use this feature