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44 lines
946 B
44 lines
946 B
9 years ago
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# Limit number of child nodes.
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This template shows how to keep the number of child nodes in a Firebase database below a given number. This can be used to limit the number of lines of a chat history or logs.
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## Cloud Function Code
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See file [index.js](index.js) for the code.
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The dependencies are listed in [package.json](package.json).
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## Sample Database Structure
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As an example we'll be using a simple chat database structure:
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```
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/functions-project-12345
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/chat
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/key-123456
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user: "Mat",
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text: "Hey Bob!"
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/key-123457
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user: "Bob",
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text: "Hey Mat! What's Up?"
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```
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## Trigger rules
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Below is the trigger rule for the `truncate` function making sure it's triggered when a new message is added.
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```
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"functions": {
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".source": "functions",
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"truncate": {
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"triggers": {
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"database": {
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"path": "/chat/$messageid"
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}
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}
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}
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}
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```
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