This commit is contained in:
Oliver Lehmann 1989-04-17 09:41:06 +00:00
parent 801ae802cb
commit a50a43e0c7
3 changed files with 502 additions and 0 deletions

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# include <stdio.h>
# include "gen.h"
# include "../h/dbs.h"
# include "../h/aux.h"
# include "../h/pipes.h"
# include "../h/symbol.h"
# include "../h/tree.h"
# include "parser.h"
struct pipfrmt Pipebuf; /* define pipe buffer structure
also referenced in rngsend and treepr */
/*
** CALL_TREE -- send a tree to decomp (or qrymod)
*/
call_tree(qmode1, execid)
short qmode1;
int execid;
{
register int qmode;
register int retr;
fflush(stdout);
qmode = qmode1;
# ifdef xPTR2
AAtTfp(26, 0, "CALL_TREE: qm=%d\tex=%d\n", qmode, execid);
# endif
wrpipe(P_PRIME, &Pipebuf, execid, (char *) 0, qmode);
writesym(QMODE, sizeof (short), &qmode1);
if (Resrng)
{
# ifdef xPTR2
AAtTfp(26, 1, "resvarno:%d\n", Resrng->rentno);
# endif
writesym(RESULTVAR, sizeof (short), &Resrng->rentno);
}
rngsend();
treepr(Lastree);
wrpipe(P_END, &Pipebuf, W_down);
/* optomize test for these two conditions */
retr = (qmode == (int) mdRETR || qmode == (int) mdRET_UNI);
/* output sync block to EQL if necessary */
if (Eql && retr && Resrng == 0)
syncup();
syncdn();
if (retr)
{
if (Resrng)
{
if (Relspec)
{
setp(Resrng->relnm);
setp(Relspec);
call_p(mdMODIFY, EXEC_DBU);
}
}
else if (!Eql)
AAendhdr();
}
}
/*
** WRITESYM -- does the physical write stuff, etc.
** for a normal tree symbol. (i.e. other
** than a SOURCEID--range table entry
*/
writesym(typ, len, value)
register int typ;
register int len;
register char *value;
{
SYMBOL sym;
sym.type = typ;
sym.len = len = ctou(len);
wrpipe(P_NORM, &Pipebuf, W_down, &sym, TYP_LEN_SIZ);
if (value)
wrpipe(P_NORM, &Pipebuf, W_down, value, len);
}
/*
** RNGWRITE -- does the physical write operation, etc.
** for SOURCEID symbol (i.e. a range table entry).
*/
rngwrite(rptr)
struct rngtab *rptr;
{
register SRCID *sp;
SRCID s;
sp = &s;
((SYMBOL *) sp)->type = SOURCEID;
((SYMBOL *) sp)->len = SRC_SIZ;
sp->srcvar = rptr->rentno;
AApmove(rptr->relnm, sp->srcname, MAXNAME, ' ');
AAbmove(rptr->relnowner, sp->srcown, 2);
sp->srcstat = rptr->rstat;
wrpipe(P_NORM, &Pipebuf, W_down, sp, TYP_LEN_SIZ);
wrpipe(P_NORM, &Pipebuf, W_down, &sp->srcvar, SRC_SIZ);
# ifdef xPTR3
AAtTfp(26, 2, "srcvar:%d\tsrcname:%.12s\tsrcown:%.2s\tsrcstat:0%o\n",
sp->srcvar, sp->srcname, sp->srcown, sp->srcstat);
# endif
}

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# include "gen.h"
# include "../h/dbs.h"
# include "../h/aux.h"
# include "../h/symbol.h"
# include "../h/tree.h"
# include "qrymod.h"
/*
** VIEW.C -- view processing
**
** This module does the view processing. Basically, it operates
** by detecting all references to views and replacing them by
** references to real relations. There are a number of cases
** when it cannot do this, to whit:
**
** Syntactic problems: the view may have a domain defined as
** a non-simple value (that is, not a simple attribute), which
** is then required to take on a value. For example, if the
** view is defined as
** range of x is baserel
** define v (d = x.a / 3)
** and then referenced as
** append to v (d = 7)
** would result after query modification as
** range of x is baserel
** append to baserel (a / 3 = 7)
** which is not acceptable. Of course, there is a range of cases
** where this can be fixed, but (for the time being) we will just
** throw them all out.
**
** Disappearing tuple anomaly: the implicit qualification on
** a view allows tuples to disappear even when not a duplicate.
** For example, take a view defined as:
** range of x is baserel
** define v (d = x.a) where x.a = 4
** and issue the query
** append to v (d = 5)
** The tuple will be inserted into the base relation, but will not
** be included in the view. To solve that problem, we disallow
** updates to domains included in the qualification of the query.
** Note that this includes implicit updates, that is, an append
** with the domain missing (which implicitly appends a zero or
** blank domain).
**
** Cross product problem: a view which is defined as a cross
** product of two relations has several update anomalies. For
** example, take R1 and R2 as:
** R1 | a | b R2 | b | c
** ---|---|--- ---|---|---
** | 7 | 0 | 0 | 3
** | 8 | 0 | 0 | 4
** and issue the view definition
** range of m is R1
** range of n is R2
** define v (m.a, m.b, n.c) where m.b = n.b
** which will define a view which looks like
** view | a | b | c
** -----|---|---|---
** | 7 | 0 | 3
** | 7 | 0 | 4
** | 8 | 0 | 3
** | 8 | 0 | 4
** Now try issuing
** range of v is v
** delete v where v.a = 8 and v.c = 4
** which will try to give a view which looks like:
** view | a | b | c
** -----|---|---|---
** | 7 | 0 | 3
** | 7 | 0 | 4
** | 8 | 0 | 3
** which is of course unexpressible in R1 and R2.
**
** Multiple query problem: certain updates will require gener-
** ating multiple queries to satisfy the update on the view.
** Although this can be made to work, it won't now. Cases are
** replaces where the target list contains more than one
** relation, and appends to a view over more than one relation.
**
** To solve these problems, we dissallow the following cases:
**
** I. In a REPLACE or APPEND statement, if a 'v.d' appears
** on the LHS in the target list of the query and
** the a-fcn for 'v.d' is not a simple attribute.
** II. In REPLACE or APPEND statements, if a 'v.d' appears
** on the LHS in a target list of the query and in
** the qualification of the view.
** III. In a DELETE or APPEND statement, if the view ranges
** over more than one relation.
** IV. In a REPLACE statement, if the query resulting after
** modification of the tree, but before appending the
** view qualification Qv, has more than one variable.
** V. In any update, if an aggregate or aggregate function
** appears anywhere in the target list of the view.
**
** Note the assumption that the definition of a consistant update
** is:
** "An update is consistant if the result of
** performing the update on the view and then
** materializing that view is the same as the
** result of materializing the view and then
** performing the update."
**
** Defines:
** view -- the driver for the view algorithm.
** vrscan -- to scan the query tree and substitute
** RESDOM nodes (plus much validity checking).
** Newresvar -- the new 'Resultvar' on updates.
*/
int Newresvar; /* new result variable, becomes Resultvar */
/*
** VIEW -- driver for view processing
**
** This routine does the view processing portion of qrymod.
** Since the AA_TREE catalog can contain relations which are
** themselves views, it iterates over itself until no views
** are found. Presumably this cannot result in an infinite
** loop, although in fact it probably can; this should be
** dealt with at some time.
**
** For each range variable declared, it is checked whether
** that variable is a view. If not, it is ignored.
** Then the tree which defines
** this view is fetched from the AA_TREE catalog by 'gettree',
** which also defines any variables required by this tree
** and adjusts the tree so that the varno's contained in the
** tree correspond to the varno's in the range table.
**
** 'Subsvars' and 'vrscan' really do it. Given the root of the tree
** to be modified, the variable number to be eliminated, and the
** target list for a replacement tree, they actually do the
** tacking of 'new tree' onto 'old tree'. After it is done,
** there should be no references to the old variable at all
** in the tree. 'Subsvars' scans for VAR nodes (which are
** retrieve-only, and hence are always alright); 'vrscan' scans
** the left hand branch of the tree (the RESDOM nodes) and
** substitutes them.
**
** 'Appqual' appends the qualification for the view (if any)
** onto the tree. Finally, the variable for the view (which
** had all references to it eliminated by 'subsvars') is un-
** defined, so that that slot in the range table can be re-
** used by later scans.
**
** Parameters:
** root -- root of the tree to be modified.
**
** Returns:
** Root of modified tree.
**
** Side Effects:
** The range table is updated to delete any views and
** add any base relations needed to support them.
** Activity occurs in the AA_TREE catalog to get the trees
** needed to define the views.
** The tree pointed to by 'root' is modified.
*/
QTREE *view(root)
QTREE *root;
{
register int vn;
register QTREE *vtree;
int viewfound;
extern QTREE *gettree();
QTREE *r;
extern QTREE *norml();
# ifdef xQTR1
AAtTfp(30, -1, "VIEW\n");
# endif
r = root;
/* scan range table until no views */
viewfound = TRUE;
while (viewfound)
{
# ifdef xQTR2
AAtTfp(30, 1, "scanning Rangev\n");
# endif
/* scan range table for views */
viewfound = FALSE;
/* make new resultvar old resultvar for non-update */
Newresvar = Resultvar;
/* scan all variables in range table */
for (vn = 0; vn < MAXVAR + 1; vn++)
{
/* check for empty entry in range table */
if (!Rangev[vn].rused)
continue;
/* see if it is a view or base relation */
if ((Rangev[vn].rstat & S_VIEW) == 0)
continue;
# ifdef xQTR1
AAtTfp(30, 3, "VIEW: vn %d: %.12s\n", vn, Rangev[vn].relid);
# endif
vtree = gettree(Rangev[vn].relid, Rangev[vn].rowner, mdVIEW, 0, FALSE);
# ifdef xQTR3
if (AAtTf(30, 5))
treepr(vtree, "Viewdef");
# endif
/* check for updating with aggregates */
if (Qmode != (int) mdRETR && aggcheck(vtree))
far_error(3350, Qmode, Resultvar, (char *) 0); /* cannot update views with aggregates */
/* scan view replacing RESDOM nodes */
if (Qmode != (int) mdRETR && vn == Resultvar)
vrscan(&r->left, vtree);
/* scan view replacing VAR nodes */
subsvars(&r, vn, vtree->left, mdVIEW);
/* test for non-functional replace */
if (Qmode == (int) mdREPL && bitcnt(varset(r) | (1 << Newresvar)) > 1)
far_error(3360, Qmode, Resultvar, (char *) 0); /* non-functional update */
/* append new qualification */
appqual(vtree->right, r);
/* delete view range variable */
Rangev[vn].rused = FALSE;
/* mark the view as having been processed */
viewfound = TRUE;
/* change 'Resultvar' to be the base rel var */
Resultvar = Newresvar;
}
}
/* renormalize the tree (just in case) */
r->right = norml(trimqlend(r->right));
# ifdef xQTR1
if (AAtTf(30, 15))
treepr(r, "VIEW->");
# endif
return (r);
}
/*
** VRSCAN -- scan query tree and replace RESDOM nodes
**
** The query tree issued is scanned and RESDOM nodes are
** converted to conform to the underlying base relations.
** There are many checks in here, and things can fail
** easily.
**
** The first check is for more than one relation in a
** DELETE or APPEND command. This would require expanding
** the query into at least two queries. For DELETE commands,
** this is the only check. (Note that by this time 'aggcheck'
** has aborted anything which would cause problems with
** aggregates.)
**
** For append commands, we abort immediately if there is
** a qualification on the view, since the inserted tuple(s)
** might not (all) appear in the view.
**
** For all other queries, the target list of the query submitted
** is scanned down the left hand side (the RESDOM list).
** For each RESDOM, that variable is looked up in the view
** definition. If the definition of it is not a simple
** attribute, the query is aborted.
**
** Then, if the variable appears anywhere in the qualification
** of the view, the query is aborted.
**
** Finally, we keep track of the varno which should become the
** new number two (that is, the Resultvar). If there are two
** candidates for this position, we promptly abort.
**
** And as the last step, we actually change the 'resno' for
** this RESDOM.
**
** When we exit the loop which scans RESDOM's, we change the
** 'Resultvar' to be the new variable which we have selected.
**
** Notice that there are a number of overly restrictive
** conditions on runability. Notably, there are large classes
** of queries which can run consistantly but which violate
** either the not-in-qualification condition or the aggregate-
** free condition.
**
** Parameters:
** root -- the root of the tree to be updated.
** vtree -- the tree which defines the view.
**
** Side Effects:
** The tree pointed to by 'root' is modified.
*/
vrscan(root, vtree)
QTREE *root;
QTREE *vtree;
{
register QTREE *t;
register QTREE *v;
int i;
extern QTREE *qscan();
extern QTREE *vfind();
register QTREE *p;
t = root;
v = vtree;
/* check DELETE and APPEND cases of > 1 relation */
if (Qmode == (int) mdDEL || Qmode == (int) mdAPP)
{
/* scan target list of view for > 1 relation */
if (bitcnt(i = varset(v->left)) != 1)
far_error(3330, Qmode, Resultvar, (char *) 0); /* query would result in > 1 query */
/* this is the only check in this module for DELETES */
if (Qmode == (int) mdDEL)
{
/* set Resultvar to underlying (single) relation */
Newresvar = bitpos(i);
return;
}
/* check for a qualification on an append */
if (v->right->sym.type != QLEND)
far_error(3320, Qmode, Resultvar, (char *) 0); /* attribute in qualification of view */
}
/* scan target list of query */
i = -1;
while ((t = t->left)->sym.type != TREE)
{
if (t->sym.type != RESDOM)
AAsyserr(19063, t->sym.type);
/* check for 'tid' attribute (stuck in by DEL and REPL) */
if (((RES_NODE *) t)->resno == 0)
{
continue;
}
/* find definition for this domain in the view */
p = vfind(((RES_NODE *) t)->resno, v->left);
/* check for simple attribute */
if (p->sym.type != VAR)
far_error(3310, Qmode, Resultvar, (char *) 0); /* non-simple attribute */
/* scan qualification of view for this attribute */
if (qscan(v->right, ((VAR_NODE *) p)->varno, ((VAR_NODE *) p)->attno) != (QTREE *) 0)
far_error(3320, Qmode, Resultvar, (char *) 0); /* attribute in qualification of view */
/* check for trying to do update on two relations again */
/* this test should only be true for REPLACE commands */
if (i < 0)
i = ((VAR_NODE *) p)->varno;
else if (i != ((VAR_NODE *) p)->varno)
far_error(3330, Qmode, Resultvar, (char *) 0); /* query on two relations */
/* finally, do the substitution of resno's */
((RES_NODE *) t)->resno = ((VAR_NODE *) p)->attno;
}
/* change the result variable for the query to the underlying */
Newresvar = i;
}

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# include <stdio.h>
# include "../conf/gen.h"
main()
{
register int c;
# ifdef SETBUF
char ibuf[BUFSIZ];
char obuf[BUFSIZ];
setbuf(stdin, ibuf);
setbuf(stdout, obuf);
# endif
while ((c = getchar()) >= 0)
AAxputchar(c);
putchar('\n');
}