[doc] Document the Python memory value contract and its divergence from Java#840
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…om Java Python memory values cross the Pemja boundary into Flink state, so only recursively checkpoint-stable values survive checkpoint/restore. The docs previously advertised Java POJO/Kryo support for Python and showed an example storing a Pydantic model. Split "Supported Value Types" into a Java contract (primitives, collections, POJOs, Kryo, MemoryObject) and a Python contract (None/bool/int/float/str, list, dict[str, ...], nested MemoryObject), name the rejected Python types, note bytes is not yet supported, and show the materialize-on-write / reconstruct-on-read pattern. The Java tab is unchanged. Follows apache#839, which added the set()-time validator that enforces this Python contract. This closes part of apache#723.
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Linked issue: #723
Purpose of change
Document the Python memory value contract and why it diverges from Java. The docs previously told Python users they could store Java POJOs and Kryo "general class types" and showed an example storing a Pydantic model — but Python memory values cross the Pemja boundary into Flink state, so only recursively checkpoint-stable values survive checkpoint/restore.
This splits the "Supported Value Types" section into a Java contract (broad: primitives, collections, POJOs, Kryo,
MemoryObject) and a Python contract (None,bool,int,float,str,list,dictwithstrkeys, and nestedMemoryObject), names the rejected Python types, notes thatbytesis not yet supported, and shows the materialize-on-write / reconstruct-on-read pattern (model.model_dump(mode="json")↔Model.model_validate(...)). The Java tab and examples are unchanged.This follows up #839, which added the
set()-time validator that enforces this Python contract. It should merge after #839.Tests
Documentation only; no code change.
API
No API change.
Documentation
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