[enhance] Try to reduce the reallocation of insertPlan in the buildValuesListOfInsert

[markjenny]

topology

running the tiup playground on my laptop. 1 TiKV, 1 TiDB and 1 PD.

workload

using sysbench to create one database consist of 32 tables. There're 10000 records in each table.

sysbench oltp_update_non_index --config-file=config --threads=32 --tables=32 --table-size=10000 prepare

profile

generate the profile using the method below

curl http://{TiDBIP}:10080/debug/zip?seconds=60 --output debug.zip

the heap profile is here The most memory cost is in the fuction buildValueListOfInsert, So try to find the memory optimization.

In the file planbuilder.go, the variable insertPlan.Lists is zero value. We can init the Lists as below:

insertPlan.Lists = make([][]expression.Expression, 0, len(insert.Lists)) // my modify
insertPlan.AllAssignmentsAreConstant = true
totalTableCols := insertPlan.Table.Cols()
for i, valuesItem := range insert.Lists {
    //...
    insertPlan.Lists = append(insertPlan.Lists, exprList)
}

Can I init the insertPlan to avoid the reallocation of the slice grow?

[ZenoTan]

/label sig/planner

[wjhuang2016]

@ZenoTan
Yes, you can take a try.