# 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](https://mtab.kgraph.jp).
## Installation
```bash
pip install freaddb
```
## Usage
```python
from freaddb.db_lmdb import SIZE_1GB, DBSpec, FReadDB, ToBytes
# 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=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=ToBytes.OBJ),
# key are strings, values are python objects serialized with pickle
DBSpec(name="data2", integerkey=False, bytes_value=ToBytes.PICKLE),
# key are strings, values are bytes
DBSpec(name="data3", integerkey=False, bytes_value=ToBytes.BYTES),
# key are integers, values are list integers serialized with numpy
DBSpec(name="data4", integerkey=True, bytes_value=ToBytes.INT_NUMPY),
# key are integers, values are list integers serialized with BITMAP
DBSpec(name="data5", integerkey=True, bytes_value=ToBytes.INT_BITMAP),
# key are combination of two integers
DBSpec(name="data6", combinekey=True),
# key are combination of three integers
DBSpec(name="data7", combinekey=True),
]
# 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=SIZE_1GB)
# Add data to FReadDB
for data_name, data_items in data.items():
for key, value in data_items.items():
db.add_buff(data_name, key, value)
# db.delete_buff("data0", "One")
# 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("data6", (1, 2))
assert sample == "One"
sample = db.get_value("data7", (1, 2, 3))
assert sample == "One"
sample = db.get_value("data1", 1)
assert sample == "One"
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
print(json.dumps(db.stats(), indent=2))
```
