[tarantool-patches] Re: [PATCH v1 2/4] sql: use 64b bitmasks instead of 32b where possible

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

Thanks for the patch! See 1 comment below.

On 08/02/2019 13:52, Kirill Shcherbatov wrote:
> In some cases(like foreign keys) the SQL code is still used
> 32-bit bit mask, while 64-bit bit masks will perform better
> column optimizations. There was refactored code to work with 64b
> bitmasks where required.
> The 32b bitmasks are still used to specify constant OP_Function
> arguments because this change would require changing the P1 type
> of the VDBE p1 argument, which is not desirable. Moreover, the
> 64 function's arguments is an explicit overkill.
> 
> Part of #3571
> ---
>   src/box/alter.cc        | 10 ++-------
>   src/box/sql/delete.c    |  8 +++----
>   src/box/sql/resolve.c   | 19 ++++++-----------
>   src/box/sql/sqliteInt.h | 46 +++++++++++++++++++++++------------------
>   src/box/sql/trigger.c   | 14 ++++++-------
>   src/box/sql/update.c    | 21 ++++++++-----------
>   6 files changed, 53 insertions(+), 65 deletions(-)
> 
> diff --git a/src/box/sql/delete.c b/src/box/sql/delete.c
> index f9c42fdec..5e134ab0c 100644
> --- a/src/box/sql/delete.c
> +++ b/src/box/sql/delete.c
> @@ -484,10 +484,8 @@ sql_generate_row_delete(struct Parse *parse, struct Table *table,
>   		 */
>   		sqlite3VdbeAddOp2(v, OP_Copy, reg_pk, first_old_reg);
>   		for (int i = 0; i < (int)table->def->field_count; i++) {
> -			testcase(mask != 0xffffffff && iCol == 31);
> -			testcase(mask != 0xffffffff && iCol == 32);
> -			if (mask == 0xffffffff
> -			    || (i <= 31 && (mask & MASKBIT32(i)) != 0)) {
> +			if (i >= COLUMN_MASK_SIZE ||
> +			    column_mask_fieldno_is_set(mask, i)) {

Now I see, why did you define COLUMN_MASK_SIZE. And still the problem
is in the way how you understand the last bit.
column_mask_fieldno_is_set() should check, if i >= COLUMN_MASK_SIZE, and in such
a case 'and' it with the last bit. In your code the mask is not 'smart' -
you consider fields >= 63 as set even if the last bit of the mask is 0. It is
worthy of note that literally every place of column_mask_fieldno_is_set() usage
also checks for i >= COLUMN_MASK_SIZE.

>   				sqlite3ExprCodeGetColumnOfTable(v, table->def,
>   								cursor, i,
>   								first_old_reg +