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Realtime Database - reading data gives wrong value if transaction is pending

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#2,634 0 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
javascript, node.js
Domain
database

Research direction

Start with the Node.js reproduction using admin.database().ref(...).transaction(...) followed by a parent ref.once('value', ...), and compare the returned array with and without the transaction. Read the Realtime Database transaction and read behavior to determine the intended result; done means the pending-transaction case is corrected or explicitly resolved as intended.

Written by the indexing model from the issue text.

Description

api: database
[REQUIRED] Step 2: Describe your environment
  • Operating System version: macOS 14.5 (23F79)
  • Firebase SDK version: 12.2.0
  • Firebase Product: database
  • Node.js version: v20.13.0
  • NPM version: v10.5.2
[REQUIRED] Step 3: Describe the problem

If a transaction is pending for a node, it doesn't show up when reading data for the parent node with .once("value", ...). I'm not sure if this is a bug or intended behavior.

Steps to reproduce:

For these examples, our database looks like this:

{
  "example_list": [
    "a",
    "b",
    "c"
  ]
}

This code works as expected:

let ref = admin.database().ref("example_list");

ref.once('value', (snap) => {
    console.log(snap.val())
});

Logs: [ 'a', 'b', 'c' ]

This code does NOT work as expected:

admin.database().ref("example_list/1").transaction((currentData) => {
    return currentData;
});

let ref = admin.database().ref("example_list");

ref.once('value', (snap) => {
    console.log(snap.val())
});

Logs: [ 'a', <1 empty item>, 'c' ]

Adding a transaction first, which seems like a no-op, actually causes the read to return a different result.

Dominant language
TypeScript
Stars
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Forks
419
Avg merge
4d 20h
Merged PRs (30d)
16

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