Create blockResultColumn.forEachDictValue* helper functions for visiting matching
dictionary values. These helper functions should prevent from counting dictionary values
without matching logs in the future.
This is a follow-up for 0c0f013a60
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/7152
This improves performance for analytical queries, which do not need column headers metadata.
For example, the following query doesn't need column headers metadata, since _stream and min(_time)
are stored in block header, which is read separately from colum headers metadata:
_time:1w | stats by (_stream) min(_time) min_time
This commit significantly improves the performance for this query.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/7070
Substitute global streamTagsCache with per-blockSearch cache for ((stream.id) -> (_stream value)) entries.
This improves scalability of obtaining _stream values on a machine with many CPU cores, since every CPU
has its own blockSearch instance.
This also should reduce memory usage when querying logs over big number of streams, since per-blockSearch
cache of ((stream.id) -> (_stream value)) entries is limited in size, and its lifetime is bounded by a single query.
The TryParseTimestampRFC3339Nano() must properly parse RFC3339 timestamps with timezone offsets.
While at it, make tryParseTimestampISO8601 function private in order to prevent
from improper usage of this function from outside the lib/logstorage package.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/6508
