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part: Fix MapTxn reusability #140

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Merged
joamaki merged 2 commits into from
Jan 27, 2026
Merged

part: Fix MapTxn reusability #140

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6e060d9
part: Test MapTxn reusability with non-singleton
joamaki Jan 26, 2026
73f0877
part: Fix MapTxn reusability
joamaki Jan 26, 2026
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27 changes: 23 additions & 4 deletions part/map_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -368,19 +368,38 @@ func TestMapTxn(t *testing.T) {
assert.Equal(t, 88, v)
tree = txn.Commit()

// Transaction can be reused after commit
// Transaction can be reused after commit (singleton case)
assert.Nil(t, tree.tree.root)
assert.False(t, tree.hasTree)
txn.Set("baz", 99)
mp = maps.Collect(txn.All())
assert.Len(t, mp, 2)
assert.Equal(t, map[string]int{"bar": 88, "baz": 99}, mp)
mp = maps.Collect(tree.All())
assert.Len(t, mp, 1)
assert.Equal(t, map[string]int{"bar": 88}, mp)
mp = maps.Collect(txn.All())
assert.Len(t, mp, 2)
assert.Equal(t, map[string]int{"bar": 88, "baz": 99}, mp)

// Set again since All() bumps txnID
txn.Set("baz", 99)
tree = txn.Commit()

// Transaction can be reused after commit (non-singleton case)
assert.NotNil(t, tree.tree.root)
assert.True(t, tree.hasTree)
txn.Set("baz", 999)

mp = maps.Collect(tree.All())
assert.Len(t, mp, 2)
assert.Equal(t, map[string]int{"bar": 88, "baz": 99}, mp)

mp = maps.Collect(txn.All())
assert.Len(t, mp, 2)
assert.Equal(t, map[string]int{"bar": 88, "baz": 999}, mp)

tree = txn.Commit()
mp = maps.Collect(tree.All())
assert.Len(t, mp, 2)
assert.Equal(t, map[string]int{"bar": 88, "baz": 999}, mp)
}

func TestUint64Map(t *testing.T) {
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4 changes: 2 additions & 2 deletions part/tree.go
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Expand Up @@ -19,7 +19,7 @@ type Tree[T any] struct {
size int // the number of objects in the tree
opts options
prevTxn *atomic.Pointer[Txn[T]] // the previous txn for reusing the allocation
prevTxnID uint64 // the transaction ID that produced this tree
nextTxnID uint64 // the next transaction ID to use
}

// New constructs a new tree.
Expand Down Expand Up @@ -74,7 +74,7 @@ func (t *Tree[T]) Txn() *Txn[T] {
txn.rootWatch = t.rootWatch
txn.size = t.size
txn.prevTxn = t.prevTxn
txn.txnID = t.prevTxnID + 1
txn.txnID = t.nextTxnID
return txn
}

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5 changes: 3 additions & 2 deletions part/txn.go
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Expand Up @@ -65,7 +65,7 @@ func (txn *Txn[T]) Clone() Tree[T] {
rootWatch: txn.rootWatch,
size: txn.size,
prevTxn: txn.prevTxn,
prevTxnID: txn.txnID,
nextTxnID: txn.txnID,
}
}

Expand Down Expand Up @@ -185,13 +185,14 @@ func (txn *Txn[T]) Commit() Tree[T] {
validateTree(txn.oldRoot, nil, nil, txn.txnID)
validateTree(txn.root, nil, txn.watches, txn.txnID)
}
txn.txnID++
t := Tree[T]{
opts: txn.opts,
root: txn.root,
rootWatch: newRootWatch,
size: txn.size,
prevTxn: txn.prevTxn,
prevTxnID: txn.txnID,
nextTxnID: txn.txnID,
}
// Store this txn in the tree to reuse the allocation next time.
t.prevTxn.Store(txn)
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