Package org.apache.kafka.streams.state

Interface ReadOnlyWindowStore<K,V>

Type Parameters:

K - Type of keys

V - Type of values

All Known Subinterfaces:

WindowStore<K,V>

public interface ReadOnlyWindowStore<K,V>

A window store that only supports read operations Implementations should be thread-safe as concurrent reads and writes are expected.

Method Summary

Modifier and Type	Method	Description
KeyValueIterator<Windowed<K>,V>	all()	Gets all the key-value pairs in the existing windows.
V	fetch(K key, long time)	Get the value of key from a window.
WindowStoreIterator<V>	fetch(K key, long timeFrom, long timeTo)	Get all the key-value pairs with the given key and the time range from all the existing windows.
KeyValueIterator<Windowed<K>,V>	fetch(K from, K to, long timeFrom, long timeTo)	Get all the key-value pairs in the given key range and time range from all the existing windows.
KeyValueIterator<Windowed<K>,V>	fetchAll(long timeFrom, long timeTo)	Gets all the key-value pairs that belong to the windows within in the given time range.

Method Detail

fetch

V fetch(K key,
        long time)

Get the value of key from a window.

Parameters:

key - the key to fetch

time - start timestamp (inclusive) of the window

Returns:

The value or null if no value is found in the window

Throws:

InvalidStateStoreException - if the store is not initialized

java.lang.NullPointerException - If null is used for any key.

fetch

WindowStoreIterator<V> fetch(K key,
                             long timeFrom,
                             long timeTo)

Get all the key-value pairs with the given key and the time range from all the existing windows. This iterator must be closed after use.

The time range is inclusive and applies to the starting timestamp of the window. For example, if we have the following windows:

 +-------------------------------+
 |  key  | start time | end time |
 +-------+------------+----------+
 |   A   |     10     |    20    |
 +-------+------------+----------+
 |   A   |     15     |    25    |
 +-------+------------+----------+
 |   A   |     20     |    30    |
 +-------+------------+----------+
 |   A   |     25     |    35    |
 +--------------------------------
 

And we call store.fetch("A", 10, 20) then the results will contain the first three windows from the table above, i.e., all those where 10 <= start time <= 20.

For each key, the iterator guarantees ordering of windows, starting from the oldest/earliest available window to the newest/latest window.

Parameters:

key - the key to fetch

timeFrom - time range start (inclusive)

timeTo - time range end (inclusive)

Returns:

an iterator over key-value pairs <timestamp, value>

Throws:

InvalidStateStoreException - if the store is not initialized

java.lang.NullPointerException - If null is used for key.

fetch

KeyValueIterator<Windowed<K>,V> fetch(K from,
                                      K to,
                                      long timeFrom,
                                      long timeTo)

Get all the key-value pairs in the given key range and time range from all the existing windows. This iterator must be closed after use.

Parameters:

from - the first key in the range

to - the last key in the range

timeFrom - time range start (inclusive)

timeTo - time range end (inclusive)

Returns:

an iterator over windowed key-value pairs <Windowed<K>, value>

Throws:

InvalidStateStoreException - if the store is not initialized

java.lang.NullPointerException - If null is used for any key.

all

KeyValueIterator<Windowed<K>,V> all()

Gets all the key-value pairs in the existing windows.

Returns:

an iterator over windowed key-value pairs <Windowed<K>, value>

Throws:

InvalidStateStoreException - if the store is not initialized

fetchAll

KeyValueIterator<Windowed<K>,V> fetchAll(long timeFrom,
                                         long timeTo)

Gets all the key-value pairs that belong to the windows within in the given time range.

Parameters:

timeFrom - the beginning of the time slot from which to search (inclusive)

timeTo - the end of the time slot from which to search (inclusive)

Returns:

an iterator over windowed key-value pairs <Windowed<K>, value>

Throws:

InvalidStateStoreException - if the store is not initialized

java.lang.NullPointerException - if null is used for any key