Revert "refactor(vmstorage): Refactor the code to reduce the time complexity of MustAddRows and improve readability (#6629)"

This reverts commit e280d90e9a.

Reason for revert: the updated code doesn't improve the performance of table.MustAddRows for the typical case
when rows contain timestamps belonging to ptws[0].

The performance may be improved in theory for the case when all the rows belong to partiton other than ptws[0],
but this partition is automatically moved to ptws[0] by the code at lines
6aad1d43e9/lib/storage/table.go (L287-L298) ,
so the next time the typical case will work.

Also the updated code makes the code harder to follow, since it introduces an additional level of indirection
with non-trivial semantics inside table.MustAddRows - the partition.TimeRangeInPartition() function.
This function needs to be inspected and understood when reading the code at table.MustAddRows().
This function depends on minTsInRows and maxTsInRows vars, which are defined and initialized
many lines above the partition.TimeRangeInPartition() call. This complicates reading and understanding
the code even more.

The previous code was using clearer loop over rows with the clear call to partition.HasTimestamp()
for every timestamp in the row. The partition.HasTimestamp() call is used in the table.MustAddRows()
function multiple times. This makes the use of partition.HasTimestamp() call more consistent,
easier to understand and easier to maintain comparing to the mix of partition.HasTimestamp() and partition.TimeRangeInPartition()
calls.

Aslo, there is no need in documenting some hardcore software engineering refactoring at docs/CHANGLELOG.md,
since the docs/CHANGELOG.md is intended for VictoriaMetrics users, who may not know software engineering.
The docs/CHANGELOG.md must document user-visible changes, and the docs must be concise and clear for VictoriaMetrics users.
See https://docs.victoriametrics.com/contributing/#pull-request-checklist for more details.

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6629

docs/CHANGELOG.md

@@ -33,7 +33,6 @@ See also [LTS releases](https://docs.victoriametrics.com/lts-releases/).
 
 * SECURITY: upgrade base docker image (Alpine) from 3.20.1 to 3.20.2. See [alpine 3.20.2 release notes](https://alpinelinux.org/posts/Alpine-3.20.2-released.html).
 
-* FEATURE: [VictoriaMetrics Single-Node](https://docs.victoriametrics.com/) and [VictoriaMetrics Cluster](https://docs.victoriametrics.com/cluster-victoriametrics/): Refactor the code located in the `MustAddRows` function of `vmstorage` to improve performance and readability.
 * FEATURE: [vmauth](./vmauth.md): add `keep_original_host` option, which can be used for proxying the original `Host` header from client request to the backend. By default the backend host is used as `Host` header when proxying requests to the configured backends. See [these docs](./vmauth.md#host-http-header).
 * FEATURE: [vmauth](./vmauth.md) now returns HTTP 502 status code when all upstream backends are not available. Previously, it returned HTTP 503 status code. This change aligns vmauth behavior with other well-known reverse-proxies behavior.
 

lib/storage/partition.go

@@ -849,11 +849,6 @@ func (pt *partition) HasTimestamp(timestamp int64) bool {
 	return timestamp >= pt.tr.MinTimestamp && timestamp <= pt.tr.MaxTimestamp
 }
 
-// TimeRangeInPartition returns true if the pt contains the given time range.
-func (pt *partition) TimeRangeInPartition(minTimestamp, MaxTimestamp int64) bool {
-	return minTimestamp >= pt.tr.MinTimestamp && MaxTimestamp <= pt.tr.MaxTimestamp
-}
-
 // GetParts appends parts snapshot to dst and returns it.
 //
 // The appended parts must be released with PutParts.

lib/storage/table.go

@@ -267,12 +267,7 @@ func (tb *table) MustAddRows(rows []rawRow) {
 	if len(rows) == 0 {
 		return
 	}
-	// Get the maximum and minimum timestamps in the rows
+
-	maxTsInRows, minTsInRows := rows[0].Timestamp, rows[0].Timestamp
-	for i := range rows {
-		maxTsInRows = max(maxTsInRows, rows[i].Timestamp)
-		minTsInRows = min(minTsInRows, rows[i].Timestamp)
-	}
 	// Verify whether all the rows may be added to a single partition.
 	ptwsX := getPartitionWrappers()
 	defer putPartitionWrappers(ptwsX)
@@ -280,7 +275,14 @@ func (tb *table) MustAddRows(rows []rawRow) {
 	ptwsX.a = tb.GetPartitions(ptwsX.a[:0])
 	ptws := ptwsX.a
 	for i, ptw := range ptws {
-		if !ptw.pt.TimeRangeInPartition(minTsInRows, maxTsInRows) {
+		singlePt := true
+		for j := range rows {
+			if !ptw.pt.HasTimestamp(rows[j].Timestamp) {
+				singlePt = false
+				break
+			}
+		}
+		if !singlePt {
 			continue
 		}