Custom name for index

[alexneisc]

I suggest adding the ability to set custom names for the index.

Postgresql has a length limit on the index name.

These two indexes will have the same name:
create_index :items, [:column1, :column2, :column3, :column4, :column5, :column6, :column7, :column8]
create_index :items, [:column1, :column2, :column3, :column4, :column5, :column6, :column7, :column8, :column9, :column10]

The name will be "items_column1_column2_column3_column4_column5_column6_column7_c". So when creating the second index, an error occurs:
relation "items_column1_column2_column3_column4_column5_column6_column7_c" already exists (Exception)

In this case, we can set a custom name for the second index and avoid the error.
create_index :items, [:column1, :column2, :column3, :column4, :column5, :column6, :column7, :column8], name: :all_columns_index

This can help with the problem from #367

[paulcsmith]

Thanks for adding this! This will be super helpful. Just a couple small suggestions.

Also, if you're up for it: what do you think about outputting a warning if the index name is too long and will be truncated by Postgres? Something like "The index name 'the_long_name' will be truncated to 'truncated' by Postgres. Consider adding a custom 'name' for this index" This would be in a separate PR though so we can get this in quick :D

And no worries if you don't have time! I can open an issue about it to tackle it later

[paulcsmith]

Suggested change

	def initialize(@table : Symbol, @columns : Columns | Nil = nil, @if_exists = false, @on_delete = :do_nothing, @name : String? | Symbol? = nil)
	end
	@columns : Columns?
	@name : Symbol | String | Nil
	def initialize(@table : Symbol, @columns : Columns, @if_exists = false, @on_delete = :do_nothing)
	end
	def initialize(@table : Symbol, @name : String | Symbol, @if_exists = false, @on_delete = :do_nothing)
	end

This makes it so you can't leave both column and string blank, and makes it clear only one should be used but not both

[alexneisc]

@paulcsmith Hm. Good point. Looks great. But there is some ambiguity.
alias Columns = Symbol | Array(Symbol)

If I send the parameter as a String, I get @name. But if I send the parameter as a Symbol, I get @columns. I think this can be confusing.

I'm not sure how to do the right thing. What do you think?

[paulcsmith]

I believe you can remove this if the the initializers ensure that one or the other is set since this will never be hit

[alexneisc]

@paulcsmith Thanks for your comment! I am happy to do something useful for Lucky :)

Tomorrow I will deal with the changes. I will definitely deal with the warning about the length of the index. This is an exciting task for me

[paulcsmith]

@alexneisc Thank you so much! Glad it is exciting work :D

[alexneisc]

@paulcsmith As I mentioned earlier, Columns is of type Symbol | Array (Symbol). So if we want to remove index by its name, we can accidentally delete the index by column. alias Columns = Symbol | Array(Symbol)

So I left the previous code with a little change. Now it has become a little more compact.

Ready for suggestions for improving the code :)

[jwoertink]

Thanks for doing this! I can see a few semantic changes we could make later, but as for functionality, this is great. I'm gonna 👍 and we can worry about clean up stuff in some later PRs.

[paulcsmith]

Agreed. We can do some method signature cleanup later since it is more complex than I thought! Thanks for the clear explanation and the nice work on this @alexneisc