Add ability to set minValidTime in TSDB (prometheus#8415)

Signed-off-by: Goutham Veeramachaneni <[email protected]>

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Signed-off-by: Goutham Veeramachaneni <[email protected]>

Author: gouthamve

tsdb/head.go

@@ -752,6 +752,11 @@ func (h *Head) Init(minValidTime int64) error {
 	return nil
 }
 
+// SetMinValidTime sets the minimum timestamp the head can ingest.
+func (h *Head) SetMinValidTime(minValidTime int64) {
+	h.minValidTime.Store(minValidTime)
+}
+
 func (h *Head) loadMmappedChunks() (map[uint64][]*mmappedChunk, error) {
 	mmappedChunks := map[uint64][]*mmappedChunk{}
 	if err := h.chunkDiskMapper.IterateAllChunks(func(seriesRef, chunkRef uint64, mint, maxt int64, numSamples uint16) error {