[tarantool-patches] Re: [PATCH 1/2 v2] test: check that collations isn't ignored in SELECTs

[n.pettik]

> On 24 Jun 2019, at 13:54, Roman Khabibov <roman.habibov at tarantool.org> wrote:
> 
> Add test to check that a new collation isn't ignored regardless
> of a name of a previous one in the following patterns of quries:

Nit: quries -> queries

> 
> SELECT s COLLATE "unicode_ci" FROM a ORDER BY s COLLATE “unicode_ci"

Why do you consider this kind of query? What can be wrong with it?
Specifying collation for result set members doesn’t make much sense btw.

> 
> Also note: It is disallowed to compare strings with different
> collations: ISO/IEC JTC 1/SC 32, Part 2: Foundation, page 531
> ---
> src/box/sql/resolve.c           |  7 +++++++
> test/sql-tap/collation.test.lua | 19 ++++++++++++++++++-
> 2 files changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/src/box/sql/resolve.c b/src/box/sql/resolve.c
> index fdf3703da..348b3ea9a 100644
> --- a/src/box/sql/resolve.c
> +++ b/src/box/sql/resolve.c
> @@ -109,6 +109,13 @@ resolveAlias(Parse * pParse,	/* Parsing context */
> 		return;
> 	if (zType[0] != 'G')
> 		incrAggFunctionDepth(pDup, nSubquery);
> +	/*
> +	 * If there was typed more than one explicit collations in
> +	 * query, it will be a sequence of left nodes with the
> +	 * collations in a tree. There is nothing special about
> +	 * keeping the sequence. Only one collation could be
> +	 * stored, but the present solution is simpler.
> +	 */

Do not understand how mentioned example is related to this code.
I suppose you might mean example like:

SELECT s COLLATE “unicode” COLLATE “binary” COLLATE “unicode_ci” …

Is this syntax allowed by ANSI? If so, which one (first or last) collation must be used?

> 	if (pExpr->op == TK_COLLATE) {
> 		pDup =
> 		    sqlExprAddCollateString(pParse, pDup, pExpr->u.zToken);
> diff --git a/test/sql-tap/collation.test.lua b/test/sql-tap/collation.test.lua
> index 79547361c..f36540fc2 100755
> --- a/test/sql-tap/collation.test.lua
> +++ b/test/sql-tap/collation.test.lua
> @@ -1,6 +1,6 @@
> #!/usr/bin/env tarantool
> test = require("sqltester")
> -test:plan(174)
> +test:plan(177)
> 
> local prefix = "collation-"
> 
> @@ -529,4 +529,21 @@ test:do_catchsql_test(
>         'CREATE TABLE test3 (a int, b int, c int, PRIMARY KEY (a, a COLLATE foo, b, c))',
>         {1, "Collation 'FOO' does not exist"})
> 
> +-- gh-3805 Check that collation is not ignored.

Why these test cases are related to the mentioned ticket?
Which collation might be ignored? I see two collations in
two different parts of query. First one is used during sorting
routines, second one is simply ignored (since values of
resulting set are not supposed to be compared with anything else).

> +
> +test:do_execsql_test(
> +    "collation-2.6.0",
> +    [[ CREATE TABLE a (id INT PRIMARY KEY, s TEXT) ]],
> +    {})
> +
> +test:do_execsql_test(
> +    "collation-2.6.1",
> +    [[ INSERT INTO a VALUES (1, 'B'), (2, 'b') ]],
> +    {})
> +
> +test:do_execsql_test(
> +    "collation-2.6.2",
> +    [[ SELECT s COLLATE "unicode_ci" FROM a ORDER BY s COLLATE "unicode" ]],
> +    {"b","B”})
> +
> test:finish_test()
> -- 
> 2.20.1 (Apple Git-117)
>