I am not sure if CL is best example - it has no NULL SQL logic.
Current issue is introduced by design, where empty array is similar to NULL (but not same) - what is on half way to Oracle varchar behave. But it is not consistent with other data types in postgres.
Pavel Stehule <pavel.stehule@gmail.com> writes: > I understand, but I don't agree. W have to fix impractical design of > arrays early. A ARRAY is 1st class - so there is not possible to use > varchar2 trick. > > if we don't would to use GUC, what do you think about compatible > extension? We can overload a system functions behave. This can solve a > problem with updates and migrations.
In Common Lisp arrays are multi-dimensional too, and the 1-D arrays have a specific name, they call them vectors. If you create an array with only 1 dimension, then it's a vector. All the array API works the same on vectors.
I guess we could specialize some of our API on vectors and avoid having to tell the system which dimension we are interested into when using them rather than multi-dimensional arrays.
Now from the internals perspective I also guess we don't want to be generating so many more types so maybe we would need some tricks to know how to promote a 1-D array into a vector automatically? -- Dimitri Fontaine http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support
