def cache(self):
"""
Yields and caches the current DataFrame.
The Koalas DataFrame is yielded as a protected resource and its corresponding
data is cached which gets uncached after execution goes of the context.
If you want to specify the StorageLevel manually, use :meth:`DataFrame.spark.persist`
See Also
--------
DataFrame.spark.persist
Examples
--------
>>> df = ks.DataFrame([(.2, .3), (.0, .6), (.6, .0), (.2, .1)],
... columns=['dogs', 'cats'])
>>> df
dogs cats
0 0.2 0.3
1 0.0 0.6
2 0.6 0.0
3 0.2 0.1
>>> with df.spark.cache() as cached_df:
... print(cached_df.count())
...
dogs 4
cats 4
Name: 0, dtype: int64
>>> df = df.spark.cache()
>>> df.to_pandas().mean(axis=1)
0 0.25
1 0.30
2 0.30
3 0.15
dtype: float64
To uncache the dataframe, use `unpersist` function
>>> df.spark.unpersist()
"""
from databricks.koalas.frame import CachedDataFrame
self._kdf._update_internal_frame(
self._kdf._internal.resolved_copy, requires_same_anchor=False
)
return CachedDataFrame(self._kdf._internal)
def persist(
self,
storage_level: StorageLevel = StorageLevel.MEMORY_AND_DISK
) -> "CachedDataFrame":
"""
Yields and caches the current DataFrame with a specific StorageLevel.
If a StogeLevel is not given, the `MEMORY_AND_DISK` level is used by default like PySpark.
The Koalas DataFrame is yielded as a protected resource and its corresponding
data is cached which gets uncached after execution goes of the context.
See Also
--------
DataFrame.spark.cache
Examples
--------
>>> import pyspark
>>> df = ks.DataFrame([(.2, .3), (.0, .6), (.6, .0), (.2, .1)],
... columns=['dogs', 'cats'])
>>> df
dogs cats
0 0.2 0.3
1 0.0 0.6
2 0.6 0.0
3 0.2 0.1
Set the StorageLevel to `MEMORY_ONLY`.
>>> with df.spark.persist(pyspark.StorageLevel.MEMORY_ONLY) as cached_df:
... print(cached_df.spark.storage_level)
... print(cached_df.count())
...
Memory Serialized 1x Replicated
dogs 4
cats 4
dtype: int64
Set the StorageLevel to `DISK_ONLY`.
>>> with df.spark.persist(pyspark.StorageLevel.DISK_ONLY) as cached_df:
... print(cached_df.spark.storage_level)
... print(cached_df.count())
...
Disk Serialized 1x Replicated
dogs 4
cats 4
dtype: int64
If a StorageLevel is not given, it uses `MEMORY_AND_DISK` by default.
>>> with df.spark.persist() as cached_df:
... print(cached_df.spark.storage_level)
... print(cached_df.count())
...
Disk Memory Serialized 1x Replicated
dogs 4
cats 4
dtype: int64
>>> df = df.spark.persist()
>>> df.to_pandas().mean(axis=1)
0 0.25
1 0.30
2 0.30
3 0.15
dtype: float64
To uncache the dataframe, use `unpersist` function
>>> df.spark.unpersist()
"""
from databricks.koalas.frame import CachedDataFrame
self._kdf._update_internal_frame(self._kdf._internal.resolved_copy,
requires_same_anchor=False)
return CachedDataFrame(self._kdf._internal,
storage_level=storage_level)
