Add prototype version of pyhdk with Calcite.

[ienkovich]

With this commit pyhdk can be installed in conda env:

mkdir build
cd build
cmake -DBUILD_SHARED_LIBS=on ..
make
make install

Calcite usage example with installed pyhdk:

$ python3
Python 3.9.12 | packaged by conda-forge | (main, Mar 24 2022, 23:25:59)
[GCC 10.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from pyhdk.sql import Calcite
>>> calcite=Calcite()
>>> print(calcite.process("SELECT 1;", "{}"))
{
  "rels": [
    {
      "id": "0",
      "relOp": "LogicalValues",
      "type": [
        {
          "type": "INTEGER",
          "nullable": false,
          "name": "ZERO"
        }
      ],
      "tuples": [
        [
          {
            "literal": 0,
            "type": "DECIMAL",
            "target_type": "INTEGER",
            "scale": 0,
            "precision": 1,
            "type_scale": 0,
            "type_precision": 10
          }
        ]
      ],
      "inputs": []
    },
    {
      "id": "1",
      "relOp": "LogicalProject",
      "fields": [
        "EXPR$0"
      ],
      "exprs": [
        {
          "literal": 1,
          "type": "DECIMAL",
          "target_type": "INTEGER",
          "scale": 0,
          "precision": 1,
          "type_scale": 0,
          "type_precision": 10
        }
      ]
    }
  ]
}
>>>

[alexbaden]

Looks nice!

I almost got it to work without Conda playing with the paths, but ran into this:

>>> from pyhdk.sql import Calcite
>>> calcite=Calcite()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "calcite.pyx", line 30, in pyhdk._sql.Calcite.__cinit__
RuntimeError: cannot find Java class CalciteServerHandler

I see the jar in my bin, but evidently it can't be found by python. Any ideas?

[ienkovich]

Looks nice!

I almost got it to work without Conda playing with the paths, but ran into this:

>>> from pyhdk.sql import Calcite
>>> calcite=Calcite()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "calcite.pyx", line 30, in pyhdk._sql.Calcite.__cinit__
RuntimeError: cannot find Java class CalciteServerHandler

I see the jar in my bin, but evidently it can't be found by python. Any ideas?

It depends on where your libs are located. The algo to find the jar file is the following:

• to check if libOSDependent.so is loaded (should be a case for python usage)
• get the dir where libOSDependent.so is placed
• add ../bin to that path and use it as a classpath for Java

We can introduce more sophisticated algo here. E. g. looking in CMAKE_INSTALL_PREFIX might be reasonable.