Thanks to the get_index_clause_from_support, we can use index for WHERE a like 'abc%' case. However this currently only works on custom plan. Think about the case where the planning takes lots of time, custom plan will not give a good result. so I want to see if we should support this for a generic plan as well.
The first step of this is we need to find an operator to present prefix is just literal. which means '%' is just '%', not match any characters. After trying 'like' and '~' operator, I find none of them can be used. for example:
PREPARE s AS SELECT * FROM t WHERE a LIKE ('^' || $1); EXECUTE s('%abc');
'%' is still a special character to match any characters. So '~' is. So I think
we need to define an new operator like text(a) ~^ text(b), which means a
is prefixed with b literally. For example:
'abc' ~^ 'ab` -> true 'abc' ~^ 'ab%' -> false
so the above case can be written as:
PREPARE s AS SELECT * FROM t WHERE a ~^ $1;
During the PoC coding, I found we already have ^@ operator for this [1], but
we don't implement that for BTree index so far. So I will try gist index for my
current user case and come back to this thread later. Thanks!
