freaddb 0.0.3

Fast Read DB

FReadDB

FReadDB: Fast Read Database is implemented with LMDB (key-value database) as the underlying storage. We use this DB as a data storage, and RAM of MTab system.

Installation

pip install freaddb

Usage

from freaddb import config
from freaddb.db_lmdb import DBSpec, FReadDB

# Data file directory
data_file = "/tmp/freaddb/db_test_basic"
# Clear old data
shutil.rmtree(data_file, ignore_errors=True)

# Define sub database schema
data_schema = [
    # keys are strings, values are python objs and compress values
    DBSpec(
        name="data0",
        integerkey=False,
        bytes_value=config.ToBytes.OBJ,
        compress_value=True,
    ),
    # key are integers, values are python objects serialized with msgpack and no compress values
    DBSpec(name="data1", integerkey=True, bytes_value=config.ToBytes.OBJ),
    # key are strings, values are python objects serialized with pickle
    DBSpec(name="data2", integerkey=False, bytes_value=config.ToBytes.PICKLE),
    # key are strings, values are bytes
    DBSpec(name="data3", integerkey=False, bytes_value=config.ToBytes.BYTES),
    # key are integers, values are list integers serialized with numpy
    DBSpec(name="data4", integerkey=True, bytes_value=config.ToBytes.INT_NUMPY),
    # key are integers, values are list integers serialized with BITMAP
    DBSpec(name="data5", integerkey=True, bytes_value=config.ToBytes.INT_BITMAP),
    # key are combination of two integers
    DBSpec(name="data6", integerkey=True, combinekey=True),
    # key are combination of three integers
    DBSpec(
        name="data7",
        integerkey=True,
        combinekey=True,
        combinelen=3,
    ),
]

# Example data
data = {
    "data0": {"One": {1: "One"}, "Two": {2: "Two"}},
    "data1": {1: "One", 2: "Two"},
    "data2": {"One": 1, "Two": 2},
    "data3": {"One": b"1", "Two": b"2"},
    "data4": {i: list(range(i * 10)) for i in range(10, 20)},
    "data5": {i: list(range(i * 10)) for i in range(10, 20)},
    "data6": {(1, 2): "One", (2, 3): "Two"},
    "data7": {(1, 2, 3): "One", (2, 3, 4): "Two"},
}
to_list_data = {"data4", "data5"}

# Create data with data_file, data_schema, and buffer is 1GB
db = FReadDB(db_file=data_file, db_schema=data_schema, buff_limit=config.SIZE_1GB)

# Add data to FReadDB
for data_name, data_items in data.items():
    for key, value in data_items.items():
        db.add(data_name, key, value)

# Make sure save all buffer to disk
db.save_buff()

####################################################
# (Optional for readonly database) Compress database
db.compress()
db.close()
db = FReadDB(db_file=data_file, readonly=True)
####################################################

# Access data
# Get a key
sample = db.get_value("data1", 1)
assert sample == "One"

# Get many keys
for data_name, data_samples in data.items():
    sample = db.get_values(data_name, list(data_samples.keys()))
    if data_name in to_list_data:
        sample = {k: list(v) for k, v in sample.items()}
    assert sample == data_samples