Do not build a superflous 'all' postings

compact.go

@@ -17,7 +17,6 @@ import (
 	"math/rand"
 	"os"
 	"path/filepath"
-	"runtime"
 	"sort"
 	"time"
 
@@ -365,10 +364,6 @@ func (c *LeveledCompactor) write(dest string, meta *BlockMeta, blocks ...BlockRe
 		}
 		c.metrics.ran.Inc()
 		c.metrics.duration.Observe(time.Since(t).Seconds())
-
-		// We might have done quite a few allocs. Enforce a GC so they do not accumulate
-		// with subsequent compactions or head GCs.
-		runtime.GC()
 	}(time.Now())
 
 	dir := filepath.Join(dest, meta.ULID.String())
@@ -570,14 +565,6 @@ func (c *LeveledCompactor) populateBlock(blocks []BlockReader, meta *BlockMeta,
 			return errors.Wrap(err, "write postings")
 		}
 	}
-	// Write a postings list containing all series.
-	all := make([]uint64, i)
-	for i := range all {
-		all[i] = uint64(i)
-	}
-	if err := indexw.WritePostings("", "", newListPostings(all)); err != nil {
-		return errors.Wrap(err, "write 'all' postings")
-	}
 
 	return nil
 }

db.go

@@ -21,6 +21,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"runtime"
 	"sort"
 	"strconv"
 	"sync"
@@ -349,9 +350,12 @@ func (db *DB) compact() (changes bool, err error) {
 		}
 		changes = true
 
+		runtime.GC()
+
 		if err := db.reload(); err != nil {
 			return changes, errors.Wrap(err, "reload blocks")
 		}
+		runtime.GC()
 	}
 
 	// Check for compactions of multiple blocks.
@@ -380,10 +384,12 @@ func (db *DB) compact() (changes bool, err error) {
 				return changes, errors.Wrap(err, "delete compacted block")
 			}
 		}
+		runtime.GC()
 
 		if err := db.reload(); err != nil {
 			return changes, errors.Wrap(err, "reload blocks")
 		}
+		runtime.GC()
 	}
 
 	return changes, nil

head.go

@@ -15,7 +15,6 @@ package tsdb
 
 import (
 	"math"
-	"runtime"
 	"sort"
 	"sync"
 	"sync/atomic"
@@ -515,8 +514,6 @@ Outer:
 
 // gc removes data before the minimum timestmap from the head.
 func (h *Head) gc() {
-	defer runtime.GC()
-
 	// Only data strictly lower than this timestamp must be deleted.
 	mint := h.MinTime()