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Compaction: Expired keys and delete markers are never purged (#1354)
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The compaction process accidentally keeps one more version of
expired keys and delete markers than it should, because of
logic error in *levelsController.compactBuildTables(). When
NumVersionsToKeep is 1, it means that expired keys and delete
markers are never actually purged from the LSM tables.

Co-authored-by: Julian Hegler <[email protected]>
Co-authored-by: Ibrahim Jarif <[email protected]>
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@damz @ou05020
3 people authored Jun 2, 2020
1 parent 543f353 commit fd89894
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Showing 2 changed files with 212 additions and 3 deletions.
8 changes: 6 additions & 2 deletions levels.go
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Original file line number Diff line number Diff line change
Expand Up @@ -585,13 +585,17 @@ func (s *levelsController) compactBuildTables(
lastValidVersion := vs.Meta&bitDiscardEarlierVersions > 0 ||
numVersions == s.kv.opt.NumVersionsToKeep

if isDeletedOrExpired(vs.Meta, vs.ExpiresAt) || lastValidVersion {
isExpired := isDeletedOrExpired(vs.Meta, vs.ExpiresAt)

if isExpired || lastValidVersion {
// If this version of the key is deleted or expired, skip all the rest of the
// versions. Ensure that we're only removing versions below readTs.
skipKey = y.SafeCopy(skipKey, it.Key())

switch {
case lastValidVersion:
// Add the key to the table only if it has not expired.
// We don't want to add the deleted/expired keys.
case !isExpired && lastValidVersion:
// Add this key. We have set skipKey, so the following key versions
// would be skipped.
case hasOverlap:
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207 changes: 206 additions & 1 deletion levels_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -139,11 +139,11 @@ func getAllAndCheck(t *testing.T, db *DB, expected []keyValVersion) {
defer it.Close()
i := 0
for it.Rewind(); it.Valid(); it.Next() {
require.Less(t, i, len(expected), "DB has more number of key than expected")
item := it.Item()
v, err := item.ValueCopy(nil)
require.NoError(t, err)
// fmt.Printf("k: %s v: %d val: %s\n", item.key, item.Version(), v)
require.Less(t, i, len(expected), "DB has more number of key than expected")
expect := expected[i]
require.Equal(t, expect.key, string(item.Key()), "expected key: %s actual key: %s",
expect.key, item.Key())
Expand Down Expand Up @@ -254,6 +254,211 @@ func TestCompaction(t *testing.T) {
getAllAndCheck(t, db, []keyValVersion{{"foo", "bar", 3, 0}, {"fooz", "baz", 1, 0}})
})
})

t.Run("level 1 to level 2 with delete", func(t *testing.T) {
t.Run("with overlap", func(t *testing.T) {
runBadgerTest(t, &opt, func(t *testing.T, db *DB) {
l1 := []keyValVersion{{"foo", "bar", 3, bitDelete}, {"fooz", "baz", 1, bitDelete}}
l2 := []keyValVersion{{"foo", "bar", 2, 0}}
l3 := []keyValVersion{{"foo", "bar", 1, 0}}
createAndOpen(db, l1, 1)
createAndOpen(db, l2, 2)
createAndOpen(db, l3, 3)

// Set a high discard timestamp so that all the keys are below the discard timestamp.
db.SetDiscardTs(10)

getAllAndCheck(t, db, []keyValVersion{
{"foo", "bar", 3, 1},
{"foo", "bar", 2, 0},
{"foo", "bar", 1, 0},
{"fooz", "baz", 1, 1},
})
cdef := compactDef{
thisLevel: db.lc.levels[1],
nextLevel: db.lc.levels[2],
top: db.lc.levels[1].tables,
bot: db.lc.levels[2].tables,
}
require.NoError(t, db.lc.runCompactDef(1, cdef))
// foo bar version 2 should be dropped after compaction. fooz
// baz version 1 will remain because overlap exists, which is
// expected because `hasOverlap` is only checked once at the
// beginning of `compactBuildTables` method.
// everything from level 1 is now in level 2.
getAllAndCheck(t, db, []keyValVersion{
{"foo", "bar", 3, bitDelete},
{"foo", "bar", 1, 0},
{"fooz", "baz", 1, 1},
})

cdef = compactDef{
thisLevel: db.lc.levels[2],
nextLevel: db.lc.levels[3],
top: db.lc.levels[2].tables,
bot: db.lc.levels[3].tables,
}
require.NoError(t, db.lc.runCompactDef(2, cdef))
// everything should be removed now
getAllAndCheck(t, db, []keyValVersion{})
})
})
t.Run("without overlap", func(t *testing.T) {
runBadgerTest(t, &opt, func(t *testing.T, db *DB) {
l1 := []keyValVersion{{"foo", "bar", 3, bitDelete}, {"fooz", "baz", 1, bitDelete}}
l2 := []keyValVersion{{"fooo", "barr", 2, 0}}
createAndOpen(db, l1, 1)
createAndOpen(db, l2, 2)

// Set a high discard timestamp so that all the keys are below the discard timestamp.
db.SetDiscardTs(10)

getAllAndCheck(t, db, []keyValVersion{
{"foo", "bar", 3, 1}, {"fooo", "barr", 2, 0}, {"fooz", "baz", 1, 1},
})
cdef := compactDef{
thisLevel: db.lc.levels[1],
nextLevel: db.lc.levels[2],
top: db.lc.levels[1].tables,
bot: db.lc.levels[2].tables,
}
require.NoError(t, db.lc.runCompactDef(1, cdef))
// foo version 2 should be dropped after compaction.
getAllAndCheck(t, db, []keyValVersion{{"fooo", "barr", 2, 0}})
})
})
})
}

func TestCompactionTwoVersions(t *testing.T) {
// Disable compactions and keep two versions of each key.
opt := DefaultOptions("").WithNumCompactors(0).WithNumVersionsToKeep(2)
opt.managedTxns = true
t.Run("with overlap", func(t *testing.T) {
runBadgerTest(t, &opt, func(t *testing.T, db *DB) {
l1 := []keyValVersion{{"foo", "bar", 3, 0}, {"fooz", "baz", 1, bitDelete}}
l2 := []keyValVersion{{"foo", "bar", 2, 0}}
l3 := []keyValVersion{{"foo", "bar", 1, 0}}
createAndOpen(db, l1, 1)
createAndOpen(db, l2, 2)
createAndOpen(db, l3, 3)

// Set a high discard timestamp so that all the keys are below the discard timestamp.
db.SetDiscardTs(10)

getAllAndCheck(t, db, []keyValVersion{
{"foo", "bar", 3, 0},
{"foo", "bar", 2, 0},
{"foo", "bar", 1, 0},
{"fooz", "baz", 1, 1},
})
cdef := compactDef{
thisLevel: db.lc.levels[1],
nextLevel: db.lc.levels[2],
top: db.lc.levels[1].tables,
bot: db.lc.levels[2].tables,
}
require.NoError(t, db.lc.runCompactDef(1, cdef))
// Nothing should be dropped after compaction because number of
// versions to keep is 2.
getAllAndCheck(t, db, []keyValVersion{
{"foo", "bar", 3, 0},
{"foo", "bar", 2, 0},
{"foo", "bar", 1, 0},
{"fooz", "baz", 1, 1},
})

cdef = compactDef{
thisLevel: db.lc.levels[2],
nextLevel: db.lc.levels[3],
top: db.lc.levels[2].tables,
bot: db.lc.levels[3].tables,
}
require.NoError(t, db.lc.runCompactDef(2, cdef))
getAllAndCheck(t, db, []keyValVersion{
{"foo", "bar", 3, 0},
{"foo", "bar", 2, 0},
})
})
})
}

func TestCompactionAllVersions(t *testing.T) {
// Disable compactions and keep all versions of the each key.
opt := DefaultOptions("").WithNumCompactors(0).WithNumVersionsToKeep(math.MaxInt32)
opt.managedTxns = true
t.Run("without overlap", func(t *testing.T) {
runBadgerTest(t, &opt, func(t *testing.T, db *DB) {
l1 := []keyValVersion{{"foo", "bar", 3, 0}, {"fooz", "baz", 1, bitDelete}}
l2 := []keyValVersion{{"foo", "bar", 2, 0}}
l3 := []keyValVersion{{"foo", "bar", 1, 0}}
createAndOpen(db, l1, 1)
createAndOpen(db, l2, 2)
createAndOpen(db, l3, 3)

// Set a high discard timestamp so that all the keys are below the discard timestamp.
db.SetDiscardTs(10)

getAllAndCheck(t, db, []keyValVersion{
{"foo", "bar", 3, 0},
{"foo", "bar", 2, 0},
{"foo", "bar", 1, 0},
{"fooz", "baz", 1, 1},
})
cdef := compactDef{
thisLevel: db.lc.levels[1],
nextLevel: db.lc.levels[2],
top: db.lc.levels[1].tables,
bot: db.lc.levels[2].tables,
}
require.NoError(t, db.lc.runCompactDef(1, cdef))
// Nothing should be dropped after compaction because all versions
// should be kept.
getAllAndCheck(t, db, []keyValVersion{
{"foo", "bar", 3, 0},
{"foo", "bar", 2, 0},
{"foo", "bar", 1, 0},
{"fooz", "baz", 1, 1},
})

cdef = compactDef{
thisLevel: db.lc.levels[2],
nextLevel: db.lc.levels[3],
top: db.lc.levels[2].tables,
bot: db.lc.levels[3].tables,
}
require.NoError(t, db.lc.runCompactDef(2, cdef))
getAllAndCheck(t, db, []keyValVersion{
{"foo", "bar", 3, 0},
{"foo", "bar", 2, 0},
{"foo", "bar", 1, 0},
})
})
})
t.Run("without overlap", func(t *testing.T) {
runBadgerTest(t, &opt, func(t *testing.T, db *DB) {
l1 := []keyValVersion{{"foo", "bar", 3, bitDelete}, {"fooz", "baz", 1, bitDelete}}
l2 := []keyValVersion{{"fooo", "barr", 2, 0}}
createAndOpen(db, l1, 1)
createAndOpen(db, l2, 2)

// Set a high discard timestamp so that all the keys are below the discard timestamp.
db.SetDiscardTs(10)

getAllAndCheck(t, db, []keyValVersion{
{"foo", "bar", 3, 1}, {"fooo", "barr", 2, 0}, {"fooz", "baz", 1, 1},
})
cdef := compactDef{
thisLevel: db.lc.levels[1],
nextLevel: db.lc.levels[2],
top: db.lc.levels[1].tables,
bot: db.lc.levels[2].tables,
}
require.NoError(t, db.lc.runCompactDef(1, cdef))
// foo version 2 should be dropped after compaction.
getAllAndCheck(t, db, []keyValVersion{{"fooo", "barr", 2, 0}})
})
})
}

func TestHeadKeyCleanup(t *testing.T) {
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