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| layout: post |
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| title: PouchDB 3.0.5: Turtles All the Way Down |
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| author: Nolan Lawson |
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| --- |
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| Tonight our fine dining selection is [PouchDB 3.0.5](https://github.com/pouchdb/pouchdb/releases/tag/3.0.5), which fixes some issues with excessive recursion and also `PouchDB.sync` not always working correctly. |
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| ### PouchDB.sync un-borked ([#2735](https://github.com/pouchdb/pouchdb/issues/2735)) |
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| You can now call `PouchDB.sync('mydb', 'http://localhost:5984/mydb')` using just the database names. |
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| Less typing === more win. |
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| ### No more infinite recursion ([#2543](https://github.com/pouchdb/pouchdb/issues/2543)) |
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| You can now have as many revisions to your documents as you want, and you'll no longer descend _Inception_-style into a "too much recursion" or "maximum call stack" error. |
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| We literally wrote [a custom JSON parser](https://github.com/nolanlawson/vuvuzela) to fix this. That's how much we love you. |
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| ### Notes on excessive revision histories |
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| The ["infinite recursion" bug](https://github.com/pouchdb/pouchdb/issues/2543) shows up when you have many (> 1000) revisions to the same document. For instance, imagine a text editor that `put()`s a new version of the document for every keystroke. This is fine in traditional databases, but it can be a big problem in PouchDB/CouchDB, because we store the entire history of the database. |
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| Make no mistake: inifinitely-large revision histories will now work in PouchDB 3.0.5. However, it's a lot like riding a bicycle without a helmet: you _can_ do it, but you probably shouldn't. |
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| Your mental model for this can be something like Git. Imagine a new `git commit` for every keystroke, and you'll see why it might be a bit problematic. |
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| ```js |
| { "text": "The quick brown fox jumps over the lazy doge." } |
| { "text": "The quick brown fox jumps over the lazy doge" } |
| { "text": "The quick brown fox jumps over the lazy dog" } |
| // |
| // 40 revisions earlier ... |
| // |
| { "text": "The q" } |
| { "text": "The " } |
| { "text": "The" } |
| { "text": "Th" } |
| { "text": "T" } |
| ``` |
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| Of course, you can always `compact()` to remove old versions, but this just removes the document data. PouchDB still needs to maintain a permanent tree of the `_rev` hashes in order for the replication algorithm to work properly. If this tree grows excessively, it can bloat your database, whether or not you do compaction. |
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| What this means is that you should be very careful about updating your documents. Try to update your documents in larger batches, or use a pattern like [delta-pouch](https://github.com/redgeoff/delta-pouch) to avoid creating new revisions altogether. |
