fiatjaf
335 lines
9.8 KiB
Go
335 lines
9.8 KiB
Go
package mmm
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import (
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"cmp"
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"encoding/binary"
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"fmt"
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"iter"
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"runtime"
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"slices"
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"syscall"
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"unsafe"
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"fiatjaf.com/nostr"
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"fiatjaf.com/nostr/eventstore/codec/betterbinary"
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"github.com/PowerDNS/lmdb-go/lmdb"
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)
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const LARGE_FREERANGE = 142
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// AllFreeRanges returns an iterator of (start_pos, size) of all free ranges, in positional order.
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func (b *MultiMmapManager) AllFreeRanges() iter.Seq2[uint64, uint32] {
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return func(yield func(uint64, uint32) bool) {
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for _, pos := range b.freeRangesAll {
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if !yield(pos.start, pos.size) {
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return
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}
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}
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}
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}
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func (b *MultiMmapManager) gatherFreeRanges(txn *lmdb.Txn) error {
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cursor, err := txn.OpenCursor(b.indexId)
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if err != nil {
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return fmt.Errorf("failed to open cursor on indexId: %w", err)
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}
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defer cursor.Close()
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usedPositions := make(positions, 0, 256)
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for key, val, err := cursor.Get(nil, nil, lmdb.First); err == nil; key, val, err = cursor.Get(key, val, lmdb.Next) {
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pos := positionFromBytes(val[0:12])
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usedPositions = append(usedPositions, pos)
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}
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// sort used positions by start
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slices.SortFunc(usedPositions, func(a, b position) int { return cmp.Compare(a.start, b.start) })
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// if there is free space at the end this will simulate it
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usedPositions = append(usedPositions, position{start: b.mmapfEnd, size: 0})
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// calculate free ranges as gaps between used positions
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b.freeRangesAll = make(positions, 0, len(usedPositions))
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b.freeRangesLarge = make([]position, 0, len(usedPositions)/10)
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var currentStart uint64 = 0
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for _, used := range usedPositions {
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if used.start > currentStart {
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// gap from currentStart to pos.start
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freeSize := used.start - currentStart
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if freeSize > 0 {
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fr := position{
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start: currentStart,
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size: uint32(freeSize),
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}
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b.freeRangesAll = append(b.freeRangesAll, fr)
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if fr.isLarge() {
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b.freeRangesLarge = append(b.freeRangesLarge, fr)
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}
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}
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}
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currentStart = used.start + uint64(used.size)
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}
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return nil
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}
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func (b *MultiMmapManager) mergeNewFreeRange(newFreeRange position) {
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// use binary search to find the insertion point for the new pos
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idx, exists := slices.BinarySearchFunc(b.freeRangesAll, newFreeRange.start, func(item position, target uint64) int {
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return cmp.Compare(item.start, target)
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})
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if exists {
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panic(fmt.Errorf("can't add free range that already exists: %s", newFreeRange))
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}
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deleteStart := -1
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deleting := 0
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// check the range immediately before
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if idx > 0 {
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before := b.freeRangesAll[idx-1]
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if before.start+uint64(before.size) == newFreeRange.start {
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deleteStart = idx - 1
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deleting++
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newFreeRange.start = before.start
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newFreeRange.size = before.size + newFreeRange.size
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}
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}
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// check the range immediately after
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if idx < len(b.freeRangesAll) {
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after := b.freeRangesAll[idx]
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if newFreeRange.start+uint64(newFreeRange.size) == after.start {
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if deleteStart == -1 {
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deleteStart = idx
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}
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deleting++
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newFreeRange.size = newFreeRange.size + after.size
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}
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}
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switch deleting {
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case 0:
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// if we are not deleting anything we must insert the new free range
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b.freeRangesAll = slices.Insert(b.freeRangesAll, idx, newFreeRange)
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// if it's large add it to the list of large free ranges
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if newFreeRange.isLarge() {
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b.freeRangesLarge = append(b.freeRangesLarge, newFreeRange)
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}
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case 1:
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deleted := b.freeRangesAll[deleteStart]
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// if we're deleting a single range, don't delete it, modify it in-place instead.
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b.freeRangesAll[deleteStart] = newFreeRange
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// if the list we're modifying is in the list of large ranges modify it there too
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if deleted.isLarge() {
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for i, large := range b.freeRangesLarge {
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if large.start == deleted.start {
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b.freeRangesLarge[i] = newFreeRange
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break
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}
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}
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} else if newFreeRange.isLarge() {
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// otherwise: if after modification it's big enough we should add it to list of large ranges
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b.freeRangesLarge = append(b.freeRangesLarge, newFreeRange)
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}
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case 2:
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// now if we're deleting two ranges, delete the second instead and modify the first in place
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first := b.freeRangesAll[deleteStart]
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second := b.freeRangesAll[deleteStart+1]
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b.freeRangesAll = slices.Delete(b.freeRangesAll, deleteStart+1, deleteStart+1+1)
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b.freeRangesAll[deleteStart] = newFreeRange
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// if the second was in the list of large lists delete it from there too
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if second.isLarge() {
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for i, large := range b.freeRangesLarge {
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if large.start == second.start {
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b.freeRangesLarge[i] = b.freeRangesLarge[len(b.freeRangesLarge)-1]
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b.freeRangesLarge = b.freeRangesLarge[0 : len(b.freeRangesLarge)-1]
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break
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}
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}
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}
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// if the list we're modifying (the first) is already in the list of large ranges modify it there too
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if first.isLarge() {
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for i, large := range b.freeRangesLarge {
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if large.start == first.start {
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b.freeRangesLarge[i] = newFreeRange
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break
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}
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}
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} else if newFreeRange.isLarge() {
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// otherwise if after modification has become big enough we should add it to list of large ranges
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b.freeRangesLarge = append(b.freeRangesLarge, newFreeRange)
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}
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}
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}
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func (b *MultiMmapManager) Defragment(n int) error {
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if b.ReadOnly {
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return ReadOnly
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}
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b.writeMutex.Lock()
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defer b.writeMutex.Unlock()
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runtime.LockOSThread()
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defer runtime.UnlockOSThread()
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if n > len(b.freeRangesAll)-1 {
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n = len(b.freeRangesAll) - 1
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}
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if n <= 0 {
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return nil
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}
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mmmtxn, err := b.lmdbEnv.BeginTxn(nil, 0)
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if err != nil {
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return fmt.Errorf("failed to begin mmm transaction: %w", err)
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}
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defer mmmtxn.Abort()
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type layerTxn struct {
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il *IndexingLayer
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txn *lmdb.Txn
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}
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layerTxns := make(map[uint16]*layerTxn)
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defer func() {
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for _, lt := range layerTxns {
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lt.txn.Abort()
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}
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}()
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// iterate only through `n` free ranges, as specified
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for i := 0; i < n; i++ {
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fr := b.freeRangesAll[i]
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// where the free range ends, the events start (any number of them)
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eventsStart := fr.start + uint64(fr.size)
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eventsEnd := b.freeRangesAll[i+1].start // and they end when the next free range starts
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c := uint64(0) // this tracks our relative position inside the events section
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for (eventsStart + c) < eventsEnd {
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var evt nostr.Event
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if err := betterbinary.Unmarshal(b.mmapf[(eventsStart+c):eventsEnd], &evt); err != nil {
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id := betterbinary.GetID(b.mmapf[(eventsStart + c):eventsEnd])
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return fmt.Errorf("failed to read event (%x) from mmap: %w", id[:], err)
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}
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// now that we have an event we'll update its pos on the id index and on every layer:
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oldVal, err := mmmtxn.Get(b.indexId, evt.ID[0:8])
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if err != nil {
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return fmt.Errorf("failed to read val (%x) from index: %w", evt.ID[:], err)
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}
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// current position
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pos := positionFromBytes(oldVal[0:12])
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// new position (from the beginning of the free range before + relative position)
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pos.start = fr.start + uint64(c)
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// update this cursor
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c += uint64(pos.size)
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// prepare and save id index
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newVal := make([]byte, len(oldVal))
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writeBytesFromPosition(newVal, pos)
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copy(newVal[12:], oldVal[12:])
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if err := mmmtxn.Put(b.indexId, evt.ID[0:8], newVal, 0); err != nil {
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return fmt.Errorf("failed to write new pos to id index: %w", err)
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}
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for s := 12; s < len(oldVal); s += 2 {
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layer := binary.BigEndian.Uint16(oldVal[s : s+2])
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lt, ok := layerTxns[layer]
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if !ok {
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il := b.layers.ByID(layer)
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if il == nil {
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fmt.Println(b.layers)
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panic(fmt.Errorf("missing layer %d", layer))
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}
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txn, err := il.lmdbEnv.BeginTxn(nil, 0)
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if err != nil {
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return fmt.Errorf("failed to begin layer txn for layer %d: %w", il.id, err)
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}
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txn.RawRead = true
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lt = &layerTxn{il: il, txn: txn}
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layerTxns[il.id] = lt
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}
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for k := range lt.il.getIndexKeysForEvent(evt) {
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if err := lt.txn.Del(k.dbi, k.key, oldVal[0:12]); err != nil {
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return fmt.Errorf("failed to delete old index entry for %x: %w", evt.ID[:], err)
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}
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if err := lt.txn.Put(k.dbi, k.key, newVal[0:12], 0); err != nil {
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return fmt.Errorf("failed to insert new index entry for %x: %w", evt.ID[:], err)
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}
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}
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}
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}
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// now that we have updated all the pointers, just copy all the bytes between the two free ranges
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copy(b.mmapf[fr.start:], b.mmapf[fr.start+uint64(fr.size):eventsEnd])
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// delete this free range if it's one of the big ones
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if fr.isLarge() {
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for l, lfr := range b.freeRangesLarge {
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if lfr.start == fr.start {
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b.freeRangesLarge[l] = b.freeRangesLarge[len(b.freeRangesLarge)-1]
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b.freeRangesLarge = b.freeRangesLarge[0 : len(b.freeRangesLarge)-1]
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break
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}
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}
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}
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// now we have some space left at the end of this events section that is a free range
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remainingSpaceStart := fr.start + c
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// it must be merged with the next free range
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updated := position{
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start: remainingSpaceStart,
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size: b.freeRangesAll[i+1].size + uint32(eventsEnd) - uint32(remainingSpaceStart),
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}
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nextWasLarge := b.freeRangesAll[i+1].isLarge()
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b.freeRangesAll[i+1] = updated
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if nextWasLarge {
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for l, lfr := range b.freeRangesLarge {
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if lfr.start == eventsEnd {
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b.freeRangesLarge[l] = updated
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break
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}
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}
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} else if updated.isLarge() {
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// if it wasn't large but now is, add it to the list of large free ranges
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b.freeRangesLarge = append(b.freeRangesLarge, updated)
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}
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}
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// msync
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_, _, errno := syscall.Syscall(syscall.SYS_MSYNC,
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uintptr(unsafe.Pointer(&b.mmapf[0])), uintptr(len(b.mmapf)), syscall.MS_SYNC)
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if errno != 0 {
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return fmt.Errorf("msync failed: %w", syscall.Errno(errno))
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}
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// commit transactions
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if err := mmmtxn.Commit(); err != nil {
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return fmt.Errorf("failed to commit mmm transaction: %w", err)
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}
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for lid, lt := range layerTxns {
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if err := lt.txn.Commit(); err != nil {
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return fmt.Errorf("failed to commit layer %d transaction: %w", lid, err)
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}
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}
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// delete the free ranges in bulk
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b.freeRangesAll = slices.Delete(b.freeRangesAll, 0, n)
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return nil
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}
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