fix: r/w concurrency

test: add case for drop dnode

fix:tag is too long if type is nchar in schemaless influxdb

fix(query): fix mode function processing all null column 

fix: read sdb when restore from raft module may cause crash

fix(query): add check for deleting record

os: backend run fail error

refactor(sync): add trace log

fix: fix taosc memory leak

TD-17024

feat(stream): add num of children

refactor(sync): update sync-timeout to 10s