Add the Snapshot action (attempt #3)

[comnik]

// Demand the source IDB, take an immutable snapshot, and turn it into an EDB
// under the given path.
message Snapshot {
  repeated string destination_path = 1;
  RelationId source_relation = 2;
}

[Copilot]

Pull request overview

This pull request adds a new Snapshot write action to the Logical Query Protocol, allowing users to capture an immutable snapshot of an IDB (Intensional Database) and turn it into an EDB (Extensional Database) under a specified path. This is the third attempt at implementing this feature.

Changes:

• Added Snapshot message to the protobuf specification with destination_path (repeated string) and source_relation (RelationId) fields
• Updated all three SDK language bindings (Python, Go, Julia) with generated protobuf code
• Extended the grammar to parse and pretty-print snapshot syntax: (snapshot ["path" "elements"] :relation_id)
• Added comprehensive test coverage demonstrating single and multi-element paths with various source relation types

Reviewed changes

Copilot reviewed 11 out of 16 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
proto/relationalai/lqp/v1/transactions.proto	Added Snapshot message definition to Write oneof (field 5, using reserved field 4 was avoided)
sdks/python/src/lqp/proto/v1/transactions_pb2.pyi	Python type stubs for Snapshot message
sdks/python/src/lqp/proto/v1/transactions_pb2.py	Python generated protobuf code for Snapshot
sdks/go/src/lqp/v1/transactions.pb.go	Go generated protobuf code with Snapshot message and getter methods
sdks/go/src/print.go	Added pretty-printing support for snapshot action using BRACKET for paths
sdks/julia/LogicalQueryProtocol/src/gen/relationalai/lqp/v1/*.jl	Julia generated protobuf code with Snapshot struct and encode/decode functions
meta/src/meta/grammar.y	Added snapshot grammar rule with construct/deconstruct for parsing and printing
tests/lqp/snapshot.lqp	Test demonstrating snapshot functionality with minimal formatting
tests/pretty/snapshot.lqp	Test with expanded/pretty-printed format including configure block
tests/bin/snapshot.bin	Binary representation of the test transaction

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[staworko]

LGTM. A couple of minor cosmetic suggestions.

[minsungc]

Can we remove logic_pb.jl and and fragments_pb.jl from the diff for clarity?

[comnik]

Actually let me file a PR against ProtoBuf.jl to stop including this information...

[minsungc]

Should we swap the fields of snapshot to be consistent with rel_edb?

I can see an argument against (in rel_edb we are "reading from" an edb and in snapshot we are "writing to" and edb), and it's not blocking, but asking anyway.

[comnik]

It was intended to reflect the read/write 🤔

[minsungc]

Promotion time ⤴️