codefever/dremel.py

Simple Python Implementation for Dremel Algorithms.

Dremel.py

paper: https://static.googleusercontent.com/media/research.google.com/zh-CN//pubs/archive/36632.pdf

Installation

pip install setup.py

Test

python -m unittest discover -t .

Usage

Dissect records

from collections import defaultdict
from dremel import writer
from document_pb2 import Document

# create writer
w = new_message_writer(Document().DESCRIPTOR, fields)

# install custom functions to store RDV data.
cols = defaultdict(list)
for leaf in w.leaf_nodes:
    leaf.set_write_callback(
        lambda node, r, d, v: cols[node.path].append((v, r, d)))

# load messages from somewhere
msgs = [...]

# dissect them
for msg in msgs:
    w.write(doc)

See also: tests/test_writer.py.

Scan/Projection

There's also a simple bridge which provides an implementation for RDV storage.

from dremel import simple, reader
from document_pb2 import Document

# create storage by the bridge
msgs = [...]
storage = simple.create_simple_storage(Document.DESCRIPTOR, msgs)
# or create your own storage

# scan!
for values, _ in reader.scan(storage, ['doc_id', 'name.url', 'name.language.code']):
    # do sth
    pass

See also: tests/test_scan.py.

Assembly

from dremel import assembly
from document_pb2 import Document

# create your own storage
storage = ...

# assemble!
builder = assembly.MessageAssemblyBuilder(storage.field_graph, Document)
assembly.assemble(storage, builder)
msgs = builder.get_msgs()  # <-results

See also: tests/test_assembly.py.