Container
#[columnar]means that some fields (marked by#[columnar(type = "vec"|"map")]) of this structure can be serialized and deserialized by columnar encoding#[columnar(vec, map)]means the struct can be a row inside [Vec] or [HashMap]#[columnar(ser, de)]means the struct can be serialized or deserialized or both by columnar encoding
Field Attributes
#[columnar(index = 1|2|3...)]: the id of the field; TODO:#[columnar(type = "vec"|"map")]:- vec means the decorated field T is a container, holds Value and satisfies
&T: IntoIter<Item=&Value>T: FromIterator<Value> - map means the decorated field T is a container, holds Value and satisfies
&T: IntoIter<Item=(&K, &Value)>T: FromIterator<(K, Value)> #[columnar(strategy = "Rle"|"BoolRle"|"DeltaRle")]: You can only choose one from the three- Rle: [
columnar::strategy::rle] - BooleanRle
- DeltaRle
#[columnar(original_type="u32")]: this attribute is used to tell the columnar encoding the original type of the field, which is used when the field is a number
Compress
-
#[columnar(compress)]: compress the columnar encoded bytes by default settings of Deflate algorithm. -
more compress options:
-
#[columnar(compress(min_size=N))]: compress the columnar encoded bytes when the size of the bytes is larger than N, default N is 256. -
#[columnar(compress(level=N))]: compress the columnar encoded bytes by Deflate algorithm with level N, N is in [0, 9], default N is 6, 0 is no compression, 9 is the best compression. See flate2 for more details. -
#[columnar(compress(method="fast"|"best"|"default"))]: compress the columnar encoded bytes by Deflate algorithm with method "fast", "best" or "default", this attribute is equivalent to#[columnar(compress(level=1|9|6))]. -
Note:
levelandmethodcan not be used at the same time.