index in meta increased for twice

[rickif]

Steps to reproduce:

influxdb 1.8, 1.7 or some other earlier versions

https://github.com/influxdata/influxdb/blob/f1d26652e91e94e050c4904818d023fe5d6701c3/services/meta/client.go

// SetData overwrites the underlying data in the meta store.
func (c *Client) SetData(data *Data) error {
	c.mu.Lock()

	// reset the index so the commit will fire a change event
	c.cacheData.Index = 0

	// increment the index to force the changed channel to fire
	d := data.Clone()
	d.Index++

	if err := c.commit(d); err != nil {
		return err
	}

	c.mu.Unlock()

	return nil
}

When func (c *Client) SetData(data *Data) error is called, the index of the data increase twice,

one for here:

influxdb/services/meta/client.go

Line 940 in f1d2665

d.Index++

another:

influxdb/services/meta/client.go

Line 970 in f1d2665

data.Index++

is that by design?

Expected behavior:

Actual behavior:

Environment info:

Config:

Logs:

Performance:

[russorat]

@rickif thanks for opening this. Is this causing an actual issue for you or are you just curious?

[rickif]

thanks for reply.
I'm just curious about this when I study the source code of influxdb 1.8.
I wonder whether it is by design and the purpose of the twice index increment.

[sebito91]

I think you might have come across a small bug @rickif! Thanks a lot for reporting this. I'm digging into the code to see exactly what impact removing the data.Index++ inside of SetData will have (as each subsequent call to commit includes an increment).

Will get back to you shortly on this.

[rickif]

maybe just removing the line below will work, since the (c *Client) commit(data *Data) error is called everytime the data changed

influxdb/services/meta/client.go

Line 940 in f1d2665

d.Index++

[rickif]

@sebito91 I've submmitied a pull request to fix this issue.
Since it's my first pr, it would be my pleasure if u could take a look
#16525