/*{
** Name: opn_bfkhget - get keyinfo structure given histogram and eqcls
**
** Description:
** Get the opb_bfkeyinfo struct that corresponds to the given
** eqclass and its associated type and length as found among the histos
** in relations histogram list. Note, that for any particular relation
** there will be a set of equivalences classes associated with that
** relation. For each equivalence class there will be exactly one
** or no histograms associated with that equivalence class.
** Thus, given the equivalence class
** and the list of histograms, the histogram associated with the
** equivalence class can be determined. For every histogram there is
** an original joinop attribute associated with it. The type and length
** associated with the joinop attribute will be used to obtain the keylist
** from the boolean factor with the same type and length.
**
** Inputs:
** subquery ptr to subquery being analyzed
** bp ptr to boolean factor which has the
** keylists
** eqc equivalence class from which a key
** element is required - there may be
** several keylists in bp associated
** with this equivalence class
** hp list of histograms associated with
** relation
**
** Outputs:
** hpp get histogram associated with
** equivalence class if this ptr is not
** NULL
** Returns:
** OPB_BFKEYINFO ptr of key associated with (equivalence class and
** histogram pair). There will only one histogram in this list with
** this equivalence class - get that histogram and use the type and
** length associated with the histogram and the input equivalence
** class to obtain the key from the boolean factor.
** Exceptions:
** none
**
** Side Effects:
** none
**
** History:
** 22-may-86 (seputis)
** initial creation
** 25-apr-94 (rganski)
** b59982 - added histdt parameter to call to opb_bfkget(). See
** comment in opb_bfkget() for more details.
{@history_line@}
[@history_line@]...
*/
OPB_BFKEYINFO *
opn_bfkhget(
OPS_SUBQUERY *subquery,
OPB_BOOLFACT *bp,
OPE_IEQCLS eqc,
OPH_HISTOGRAM *hp,
bool mustfind,
OPH_HISTOGRAM **hpp)
{
OPH_HISTOGRAM *thp; /* histogram associated with equivalence
** class eqc */
OPZ_ATTS *attrp; /* ptr to joinop attribute associated with
** histogram thp
*/
OPB_BFKEYINFO *bfkeyp; /* ptr to struct with proper equivalence
** class, type and length characteristics
*/
OPH_HISTOGRAM **thpp; /* used in case NULL is returned */
if (!(thpp = opn_eqtamp(subquery, &hp, eqc, mustfind)) )
return (NULL);
thp = *thpp;
attrp = subquery->ops_attrs.opz_base->opz_attnums[thp->oph_attribute]; /*
** get attribute pointer associated with
** histogram */
if ((bfkeyp = opb_bfkget(subquery, bp, eqc, &attrp->opz_dataval,
&attrp->opz_histogram.oph_dataval, mustfind))
== NULL)
return (NULL);
if (hpp) /* return this info if requested */
*hpp = thp;
return (bfkeyp);
}
/*{
** Name: opb_mbf - find matching boolean factors for keylist
**
** Description:
** See if there are the right matching boolean factors for
** the given attributes so that they can be used to key the
** relation.
**
** Inputs:
** subquery ptr to subquery being analyzed
** storage storage structure associated with
** keylist
** mbf matching boolean factor list
** - contains keylist on which the
** relation is ordered, but the matching
** boolean factors have not been found
**
** Outputs:
** mbf ptr to structure which will contain
** the matching boolean factors for the
** attributes in the dmfkeylist
** Returns:
** TRUE if a limiting boolean factor has been found
** Exceptions:
** none
**
** Side Effects:
** none
**
** History:
** 4-may-86 (seputis)
**
** 25-apr-94 (rganski)
** b59982 - added histdt parameter to call to opb_bfkget(). See
** comment in opb_bfkget() for more details.
** 26-oct-00 (inkdo01)
** Dropped use of OPB_SSINGLEALL since its sole purpose appeared
** to be to prevent IN-lists on lower order columns of multi-att,
** non-hash key structures. Just didn't make sense.
** 22-nov-01 (inkdo01)
** Check for "tid is null" and don't return key structure (these
** may be outer join tricks and are useless for key access).
{@history_line@}...
*/
bool
opb_mbf(
OPS_SUBQUERY *subquery,
OPO_STORAGE storage,
OPB_MBF *mbf)
{
i4 count; /* count of number of active elements in the
** the keylist
*/
mbf->opb_maorder = NULL;
if ( (count = mbf->opb_count) <= 0)
return(FALSE); /* keylist does not exist so this relation
** does not have a useful ordering for this
** query
*/
if (storage == DB_HEAP_STORE)
return(FALSE); /* heap is not useful for limiting predicates*/
{
bool rangeOk;
i4 keyi; /* offset in opb_keyorder array of
** of attribute being analyzed
*/
OPZ_AT *abase; /* base of joinop attributes array */
OPB_BFT *bfbase; /* base of boolean factor array */
OPE_ET *ebase; /* base of equivalence class array */
abase = subquery->ops_attrs.opz_base;
bfbase = subquery->ops_bfs.opb_base;
ebase = subquery->ops_eclass.ope_base;
rangeOk = (storage != DB_HASH_STORE);
for (keyi = 0; keyi < count; keyi++)
{
OPB_ATBFLST *keydesc;/* ptr to key attribute being
** analyzed */
OPZ_ATTS *ap; /* ptr to joinop attribute associated
** with key element
*/
OPE_IEQCLS eqcls; /* equivalence class of joinop
** attribute */
bool usable; /* class of best limiting boolean
** factor found so far */
usable = FALSE; /* Assume no limiting predicates */
keydesc = &mbf->opb_kbase->opb_keyorder[keyi];
ap = abase->opz_attnums[keydesc->opb_attno];
if ( (eqcls = ap->opz_equcls) >= 0)
{ /* if equivalence class exists then check if a list of limiting
** predicates is associated with the equivalence class
*/
OPB_IBF bfi; /* boolean factor number which contains
** OPB_BFGLOBAL information */
bfi = ebase->ope_eqclist[eqcls]->ope_nbf; /* get boolean factor
** which contains summary of information
** for this equivalence class */
if (bfi != OPB_NOBF) /* check if any boolean factors
** exist for this equivalence class */
{
OPB_BOOLFACT *bfp;/* ptr to boolean factor which
** contains the OPB_BFGLOBAL info
** for this equivalence class
*/
OPB_BFKEYINFO *bfinfop; /* ptr to bfkeyinfo for this
** joinop attribute (type,length)
*/
bfp = bfbase->opb_boolfact[bfi];
/* Check for "tid is null" - a predicate that's useless
** for keying. */
if (count == 1 &&
ebase->ope_eqclist[eqcls]->ope_eqctype == OPE_TID &&
bfp->opb_qnode &&
bfp->opb_qnode->pst_sym.pst_value.pst_s_op.pst_opno ==
subquery->ops_global->ops_cb->ops_server->opg_isnull)
{
mbf->opb_bfcount = 0;
return(FALSE); /* show no key from TID */
}
bfinfop = opb_bfkget( subquery, bfp, eqcls,
&ap->opz_dataval, &ap->opz_histogram.oph_dataval, TRUE);
/* get the keyinfo ptr
** for the type and length
** of the attribute, which
** contains the OPB_BFGLOBAL
** information for the
** attribute
*/
usable = opb_bestbf( bfi, bfinfop, rangeOk, keydesc);
}
}
if (!usable)
{ /* boolean factor for attribute not found so stop with
** what we have so far (if anything).
*/
if (storage == DB_HASH_STORE)
{
mbf->opb_bfcount = 0; /* boolean facts for
** all key attributes must exist
** for hash key to be built
*/
return(FALSE); /* key cannot be built */
}
mbf->opb_bfcount = keyi; /* save the number of attributes
** which have useful keys */
return( keyi > 0 ); /* partial key can be built */
}
}
}
mbf->opb_bfcount = mbf->opb_count; /* all attributes have matching boolean
** factors */
return( TRUE ); /* boolean factors were found for key */
}
