onlyIfChanged: adds option to put only if value passed is different from value at key #47
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utanapishtim
changed the title
test/all.js
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| tape('put onlyIfChanged inserts only if existing value !== value', async t => { | ||
| const Hypercore = require('hypercore') | ||
| const feed = new Hypercore(require('random-access-memory')) | ||
| const db = new Hyperbee(feed) |
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use the create helper above
test/all.js
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| tape('batch put onlyIfChanged inserts only if existing value !== value', async t => { | ||
| const Hypercore = require('hypercore') | ||
| const feed = new Hypercore(require('random-access-memory')) | ||
| const db = new Hyperbee(feed) |
test/all.js
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| const Hypercore = require('hypercore') | ||
| const feed = new Hypercore(require('random-access-memory')) | ||
| const db = new Hyperbee(feed) | ||
| await db.ready() |
test/all.js
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| const Hypercore = require('hypercore') | ||
| const feed = new Hypercore(require('random-access-memory')) | ||
| const db = new Hyperbee(feed) | ||
| await db.ready() |
| @@ -622,6 +634,15 @@ class Batch { | |||
| node = await node.getChildNode(i) | |||
| } | |||
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| if (onlyIfChanged) { | |||
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pretty sure this would never fire. the only time an existing key is found is above in c === 0
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I actually meant to add a question about this. In my testing I never triggered the loop, is there a branching factor in the bee tree that delays splits until a certain number of keys have been written? In my testing this was the branch that was exclusively hit.
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the split is only relevant for maintaining the b-tree index (see tree splitting with b-trees on wikipedia for example), so so a "put(key) when key exists" should ALWAYS hit the while above, ie it has to find the existing node first.
| if (onlyIfChanged) { | ||
| const block = await this.getBlock(node.keys[mid].seq) | ||
| const same = (Buffer.compare(block.value, value) === 0) | ||
| if (same) try { return block.final() } finally { this._unlockMaybe() } |
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if (same) return this._unlockMaybe() is fine
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This will violate the expected behavior once #46 is merged, returning block.final() satisfies the "new" expectation.
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that's fine, we'll tweak after or fix in the other PR :)
test/all.js
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| const value = Buffer.from('value') | ||
| await db.put(key, value) | ||
| const fst = await db.get(key) | ||
| const fstlen = db._feed.length |
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db.feed should be fine instead of _feed (everywhere here)
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Not needed now because of #50 |
This PR adds an
{ onlyIfChanged: Boolean }option toHyperbee.put()andHyperbee.batch().put(), constraining puts at a key to only succeed if the existing value at the key is not the same (i.e. if the encoded binary values are not the same).