Significant CPU usage for tryLockMDLAndUpdateSchemaIfNecessary for insert statement on table over 1k columns

[dbsid]

Enhancement

Even with plan cache hits, high cpu on tryLockMDLAndUpdateSchemaIfNecessary is observed, the table has over 1 thousands columns. seems the loops on tbl.Meta().Columns caused high cpu usage, need to see if anyway to optimize the cpu usage when the number of column on the table is high.

			// Check the column change.
			for _, col := range tbl.Meta().Columns {
				if col.State != model.StatePublic {
					continue
				}
				found := false
				for _, coll := range tableInfo.Columns {
					if col.Name.L == coll.Name.L && col.ID != coll.ID {
						logutil.BgLogger().Info("public column changed", zap.String("column", col.Name.L), zap.String("old_col", coll.Name.L), zap.Int64("new id", col.ID), zap.Int64("old id", coll.ID))
						found = true
						break
					}
				}
				if found {
					if !skipLock {
						sctx.GetSessionVars().GetRelatedTableForMDL().Delete(tableInfo.ID)
					}
					return nil, domain.ErrInfoSchemaChanged.GenWithStack("public column %s has changed", col.Name)
				}
			}
		}

[wjhuang2016]

I guess there is no DDL in your scenario, right?
We can simplify checking the table change by comparing Revision in tableInfo

[bb7133]

Could you please share the profiling file?