add ON CONFLICT DO NOTHING for insert

[JasonYangShadow]

in this PR, I added a new method named CreateIgnore, which will add ON CONFLICT DO NOTHING to INSERT query (https://www.postgresql.org/docs/current/sql-insert.html), it'll help avoid returning the duplicated key violation error thus application does not need to do this check at each place where Create method is called.

[WestleyK]

Can @mstg also review this?

[mstg]

I'm not fully against merging this, just not sure if introducing further operations is the best way to go. What if we used something like

type PikaOption byte

const OnConflictDoNothing PikaOption = 1 << 2

func test(a string, options ...PikaOption) {
	var opt PikaOption
	for _, v := range options {
		opt |= v
	}
	if opt&OnConflictDoNothing != 0 {
		fmt.Println("do nothing on conflict")
	} else {
		fmt.Println("fail on conflict")
	}
}

That way we could continue using Create without breaking any current usage (due to the spread operator) and we could potentially introduce other options.

@JasonYangShadow @WestleyK What do you think? We could just merge this too and get back to it later. This library is due for some changes that is going to simplify its use but that is going to be long term and gradual. I'm OK with both approaches at the moment

[WestleyK]

@mstg I like that approach better. I think we can include that in this PR if its okay with @JasonYangShadow.

[WestleyK]

Couple small comments, otherwise looks good.

[WestleyK]

So if this is intended to be a bitbask type option(s), I think this byte shift will collide, we can use this instead for unique bitmask values:

1 << iota

[JasonYangShadow]

yeah, this one looks better. thanks!

[WestleyK]

Would it make sense to call this PikaCreateOption? This is specifically create options, this is a very generic name.

[JasonYangShadow]

though I feel like this originally is designed for any pika option. but PikaCreateOption looks more clear in this case

[WestleyK]

Just a suggestion, maybe you could do something like this:

if errors.Is(err, sql.ErrNoRows) && getOptions(opts...)&InsertOnConflictionDoNothing > 0 {

...

func getOptions(opts ...PikaOption) PikaOption {
	o := 0
	if opts == nil {
		return o
	}
	for _, opt := range opts {
		o = o | opt
	}

	return o
}

You dont need to change this, just thinking, this could make it easier when (if) theres lots of options, since we dont need a dedicated function to return each option.

[WestleyK]

This looks good to me, can @mstg take another look?

[mstg]

@JasonYangShadow Could you rename PikaCreateOption to CreateOption? The linter caught that one

[JasonYangShadow]

@JasonYangShadow Could you rename PikaCreateOption to CreateOption? The linter caught that one

Thanks! done rename.

[mstg]

Awesome, thank you!