Hi, Varun!
On Aug 26, Varun Gupta wrote:
> revision-id: 25d6f575a50 (mariadb-10.4.7-31-g25d6f575a50)
> parent(s): 7b4de10477a
> author: Varun Gupta <varun.gu...@mariadb.com>
> committer: Varun Gupta <varun.gu...@mariadb.com>
> timestamp: 2019-08-22 02:38:38 +0530
> message:
>
> MDEV-19705: Assertion `tmp >= 0' failed in best_access_path
>
> The reason for hitting the assert is that rec_per_key estimates have some
> garbage value.
> So the solution to fix this would be for long unique keys to use use
> rec_per_key for only 1 keypart
>
> ---
> mysql-test/main/long_unique.result | 15 +++++++++++++++
> mysql-test/main/long_unique.test | 14 ++++++++++++++
> sql/table.cc | 13 ++++++++++++-
> 3 files changed, 41 insertions(+), 1 deletion(-)
>
> diff --git a/sql/table.cc b/sql/table.cc
> index 1ab4df0f7cf..fa57693e7eb 100644
> --- a/sql/table.cc
> +++ b/sql/table.cc
> @@ -828,6 +829,16 @@ static bool create_key_infos(const uchar *strpos, const
> uchar *frm_image_end,
> {
> keyinfo->key_length= HA_HASH_KEY_LENGTH_WITHOUT_NULL;
> key_part++; // reserved for the hash value
> + /*
> + but hash keys have a flag "only whole key", so for hash keys one
> should never
> + look at keyinfo->rec_per_key for partial keys, and they cannot
> possibly be calculated
> + so here we make sure that the
> keyinfo->rec_per_key[keyinfo->user_defined_key_parts-1]
> + would point to the slot we reserved for the keyinfo which holds the
> unique key with
> + hash
> + */
> + ulong *dest= (keyinfo->rec_per_key + keyinfo->user_defined_key_parts -
> 1);
> + memcpy(&dest, &rec_per_key, sizeof(ulong*));
Sorry, I don't understand what you're doing here.
I only meant something like
keyinfo->rec_per_key-= keyinfo->user_defined_key_parts - 1;
> + *rec_per_key++= 0;
> }
>
> /*
>
Regards,
Sergei
VP of MariaDB Server Engineering
and secur...@mariadb.org
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