# include
# include
# include
# include
# include "globs.h"
# include
SCCSID(@(#)pull_const.c 8.1 12/31/84)
/*
** PULL_CONST - Detach and execute all constant clauses in the qualification.
**
** Pull_const examines the root tree for any constant clauses.
** If none are present then it returns TRUE. If there are any
** constant clauses, then they are removed, executed and if
** TRUE then pull_const returns TRUE and other wise it returns
** FALSE.
**
** This routine is not necessary to decomposition but rather
** can be called as an optimization when constant clauses are
** expected. Note that without this routine, constant clauses
** would only be examined at the bottom level of decomposition.
** Thus a multivar query which was true except for a constant clause
** would look at the required cross-product space before returning.
*/
pull_const(root, buf)
QTREE *root;
char *buf;
{
register QTREE *r, *q, *s;
QTREE *makroot();
s = (QTREE *) NULL;
for (r = root; r->right->sym.type != QLEND; )
{
q = r;
r = r->right; /* r is now the AND node */
if (r->sym.value.sym_root.lvarc == 0)
{
/* we have a constant clause */
if (s == 0)
s = makroot(buf);
/* remove AND from root tree */
q->right = r->right;
/* put node into constant tree */
r->right = s->right;
s->right = r;
/* fix up var counts (just for good form!) */
r->sym.value.sym_root.rvarm = r->sym.value.sym_root.tvarc = 0;
r = q;
}
}
if (s)
{
/* run the constant query */
return (execsq1(s, -1, NORESULT));
}
return (TRUE);
}