Select: Allow caller to pass pointer-to-slice to have results appended

[robfig]

Maintains backwards compatibility.

(Tested with MySQL only.)

Fixes #36

[coopernurse]

Wow, thanks for the quick turnaround. I don't think I'll have time to review this tonight, but hopefully in the next day or two.

[sqs]

This patch fails the tests on PostgreSQL due to the use of the bind var ?:

--- FAIL: TestHooks (0.34 seconds)
gorptest: 16:04:15.413071 select * from person_test where id = ? [[1]]
panic: pq: S:"ERROR" C:"42601" M:"syntax error at end of input" P:"39" F:"scan.l" L:"994" R:"scanner_yyerror" [recovered]
    panic: pq: S:"ERROR" C:"42601" M:"syntax error at end of input" P:"39" F:"scan.l" L:"994" R:"scanner_yyerror"

goroutine 12 [running]:
testing.func��004()
    /home/sqs/src/go/src/pkg/testing/testing.go:348 +0xcd
gorp._rawselect(0xc20012f720, 0x5cd140, 0xc200148f20, 0x6d7a70, 0x26, ...)
    /home/sqs/src/gorp/gorp_test.go:961 +0xdf
gorp.TestHooks(0xc20012cab0)
    /home/sqs/src/gorp/gorp_test.go:438 +0x4e9
testing.tRunner(0xc20012cab0, 0xa05680)
    /home/sqs/src/go/src/pkg/testing/testing.go:353 +0x8a
created by testing.RunTests
    /home/sqs/src/go/src/pkg/testing/testing.go:433 +0x86b

After applying this diff, it passes both the PostgreSQL and SQLite tests for me:

diff --git a/gorp_test.go b/gorp_test.go
index 63485dc..6ef3e2a 100644
--- a/gorp_test.go
+++ b/gorp_test.go
@@ -435,7 +435,8 @@ func TestHooks(t *testing.T) {
        }

        var persons []*Person
-       rawselect(dbmap, &persons, "select * from person_test where id = ?", p1.Id)
+       bindVar := dbmap.Dialect.BindVar(0)
+       rawselect(dbmap, &persons, "select * from person_test where id = "+bindVar, p1.Id)
        if persons[0].LName != "postget" {
                t.Errorf("p1.PostGet() didn't run after select: %v", p1)
        }

[robfig]

Thanks for testing it out @sqs ! I applied your patch. Tests continue to pass on MySQL.

[sqs]

If you try to select into var foo []*MyType instead of a var foo *[]*MyType (e.g., you forget the & in the arg), then you get an error message that is no longer applicable with this new feature:
gorp: Cannot SELECT into non-struct type: []*MyType

I think this error message should be updated in this PR.

BTW, I've been using this new feature for a day and have simplified a bunch of my code. It's great! And it is working well.

[sqs]

I believe this breaks backcompat. Previously, an empty SQL result set would yield a empty slice return value. Now, it yields nil. (I discovered this in my code that marshals the JSON of the gorp query results; it used to be [] when empty, and now it's null.)

[sqs]

Here is a patch+testcase that ensures that results are always non-nil: https://github.com/sqs/gorp/commit/6dfc2ee1f39270fc9b5d172701610d7c2335a665

[coopernurse]

Hey guys. I'm merging this stuff into master now. @sqs I have integrated your patch+test from 6dfc2ee.

I think the only outstanding item is the error message: "gorp: Cannot SELECT into non-struct type: []*MyType"

I'm inclined to just get these commits into master, and open a separate issue for that. Just so we don't keep this work sequestered too long.

thanks guys for all your work on this! great addition.

-- James