Do not interpolate literals when prepared=true.

[marshall-mcmullen]

This addresses #132. The gist
of this fix is to modify the builders to not interpolate nil and boolean
values so that prepared statements can work properly. This makes
prepared=true work more consistently across all types.

The scope of this change:

(1) Modify literalNil to use a placeholder if prepared=true similar to
literalBool and literalInt

(2) Modify checkBoolExpType to not turn (in)equality on nil or bool
values to an IS expression.

(3) LOTS of tests and examples updated to reflect the new behavior.

[marshall-mcmullen]

I tested these changes locally with:

• ./go.test.sh
• go test -v -race ./...
• GO_VERSION=latest POSTGRES_VERSION=11.4 MYSQL_VERSION=8.0.12 docker-compose run goqu

[marshall-mcmullen]

I don't know why the file vendor/github.com/mattn/go-sqlite3/sqlite3-binding.c is showing as modified. It looks to me locally identical to what is in master. Is this expected?

[doug-martin]

These shouldn't be changed because it is using the Is methods.

[doug-martin]

This should be reverted to work like it did previously. See https://stackoverflow.com/questions/9822154/standard-sql-boolean-operator-is-vs-equals-operator is and equality work differently for NULL, TRUE and FALSE.

[doug-martin]

The is methods should work like they did previously. Take a look at https://stackoverflow.com/questions/9822154/standard-sql-boolean-operator-is-vs-equals-operator it explains the difference pretty well.

[doug-martin]

After reading through https://stackoverflow.com/questions/9822154/standard-sql-boolean-operator-is-vs-equals-operator we may want to test this out some more especially with NULL values, TRUE and FALSE will work in the case that the column is not UNKNOWN.

Here is a simple example you can run in postgres to demonstrate the problem.

select
       NULL = NULL as eq_null,
       NULL = TRUE as eq_true,
       NULL = FALSE as eq_false,
       NULL IS NULL as is_null,
       NULL IS NOT NULL as is_not_null,
       NULL IS TRUE as is_true,
       NULL IS NOT TRUE is_not_true,
       NULL IS FALSE as is_false,
       NULL IS NOT FALSE is_not_false;
select
       TRUE = NULL as eq_null,
       TRUE = TRUE as eq_true,
       TRUE = FALSE as eq_false,
       TRUE IS NULL as is_null,
       TRUE IS NOT NULL as is_not_null,
       TRUE IS TRUE as is_true,
       TRUE IS NOT TRUE is_not_true,
       TRUE IS FALSE as is_false,
       TRUE IS NOT FALSE is_not_false;

select
       FALSE = NULL as eq_null,
       FALSE = TRUE as eq_true,
       FALSE = FALSE as eq_false,
       FALSE IS NULL as is_null,
       FALSE IS NOT NULL as is_not_null,
       FALSE IS TRUE as is_true,
       FALSE IS NOT TRUE is_not_true,
       FALSE IS FALSE as is_false,
       FALSE IS NOT FALSE is_not_false;

My real concern here is NULL as goqu would effectively allow you to create SQL that does not function as one would expect, same for boolean but to a lesser extent.

[marshall-mcmullen]

Thanks for the detailed review and feedback @doug-martin. I wanted to get the SetError PR finished up first (now done!). I'll pick this one up tonight as I'd like to try to address all the issues you brought up. Thanks again!

[doug-martin]

Im closing this for now please re-open once you have it figure out. If you have any further questions don't hesitate to reach out.