[tarantool-patches] Re: [PATCH 4/5] sql: display error on FK creation and drop failure

[Vladislav Shpilevoy <v.shpilevoy@tarantool.org>]

Thanks for the patch! See 4 comments below.

On 13/07/2018 05:04, Nikita Pettik wrote:
> Before insertion to _fk_constraint we must be sure that there in no
> entry with given <name, child id>. Otherwise, insertion will fail and
> 'duplicate key' will be shown. Such error message doesn't seem to be
> informative enough, so lets manually iterate through whole space looking
> for appropriate record.

1. As I know, vdbe_emit_halt_with_presence_test do not iterate through
the whole space. It uses an index to search for the record fast.

> The same is for dropping constraint, but here vice versa: we test
> that _fk_contraint contains entry with given name and child id.

2. Typo: _fk_contraint -> _fk_constraint.

> 
> It is worth mentioning that during CREATE TABLE processing schema id
> changes and check in OP_OpenRead opcode fails (which in turn shows that
> pointer to space may expire). On the other hand, _fk_constraint space
> itself remains immutable, so as a temporary workaround lets use flag
> indicating pointer to system space passed to OP_OpenRead. It makes
> possible to use pointer to space, even if schema has changed.
> 
> Closes #3271
> ---
>   src/box/errcode.h            |  2 ++
>   src/box/sql/build.c          | 43 +++++++++++++++++++++++++++++++------------
>   src/box/sql/sqliteInt.h      | 10 +++++++---
>   src/box/sql/trigger.c        | 24 ++++++++++++++++--------
>   src/box/sql/vdbe.c           |  3 ++-
>   test/box/misc.result         |  2 ++
>   test/sql-tap/alter2.test.lua | 25 ++++++++++++++++++++++++-
>   7 files changed, 84 insertions(+), 25 deletions(-)
> 
> diff --git a/src/box/sql/build.c b/src/box/sql/build.c
> index c2d3cd035..20ace09e4 100644
> --- a/src/box/sql/build.c
> +++ b/src/box/sql/build.c
> @@ -1784,6 +1784,20 @@ vdbe_fkey_code_creation(struct Parse *parse_context, const struct fkey_def *fk)
>   		sqlite3VdbeAddOp2(vdbe, OP_Integer, fk->parent_id,
>   				  constr_tuple_reg + 2);
>   	}
> +	/*
> +	 * Lets check that constraint with this name hasn't
> +	 * been created before.
> +	 */
> +	const char *error_msg =
> +		tt_sprintf(tnt_errcode_desc(ER_CONSTRAINT_EXISTS), name_copy);
> +	if (vdbe_emit_halt_with_presence_test(parse_context,
> +					      BOX_FK_CONSTRAINT_ID, 0,
> +					      constr_tuple_reg, 2,
> +					      ER_CONSTRAINT_EXISTS, error_msg,
> +					      false, OP_NoConflict) != 0) {
> +		free((void *) name_copy);

3. Name_copy is allocated on db.

> +		return;
> +	}
> diff --git a/src/box/sql/vdbe.c b/src/box/sql/vdbe.c
> index b9723e2e7..0f227e637 100644
> --- a/src/box/sql/vdbe.c
> +++ b/src/box/sql/vdbe.c
> @@ -3172,7 +3172,8 @@ case OP_OpenWrite:
>   	 * during runtime.
>   	 */
>   	if (box_schema_version() != p->schema_ver &&
> -	    (pOp->p5 & OPFLAG_FRESH_PTR) == 0) {
> +	    (pOp->p5 & OPFLAG_FRESH_PTR) == 0 &&
> +	    (pOp->p5 & OPFLAG_SYSTEMSP) == 0) {

4. Why not p5 & (FRESH_PTR | SYSTEMSP) ?

>   		p->expired = 1;
>   		rc = SQLITE_ERROR;
>   		sqlite3VdbeError(p, "schema version has changed: " \