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List: postgresql-general
Subject: [GENERAL] Foreign Keys: check_primary_function
From: Anand Surelia <anand () bytekinc ! com>
Date: 1998-09-21 19:05:52
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Hi All,
I've changed the check_primary_key() function code to allow for either
the "automatic insert key rule" or "dependent insert key rule".
Previously it restricted the addtion of a child entry if the
corresponding parent entry was not there. Now if the option is
"automatic" it will add an entry in the parent too ( it will be
successful if there are no no-null fields in the parent apart from the
primary key).
The way to use it now is:
/*
* check_primary_key () -- check that key in tuple being
inserted/updated
* references existing tuple in "primary" table.
* Though it's called without args You have to specify referenced
* table/keys while creating trigger: key field names in triggered
table,
* referenced table name, referenced key field names,type of action
[automatic|dependent]:
* EXECUTE PROCEDURE
* check_primary_key ('Fkey1', 'Fkey2', 'Ptable', 'Pkey1', 'Pkey2',
'[automatic|dependent]').
*/
I am attaching the new ../contrib/spi/refint.c file which will do this.
I will be glad to help in case of any problems.
- Anand.
["myrefint.c" (text/plain)]
/*
* refint.c -- set of functions to define referential integrity
* constraints using general triggers.
*/
#include "executor/spi.h" /* this is what you need to work with SPI */
#include "commands/trigger.h" /* -"- and triggers */
#include <ctype.h> /* tolower () */
HeapTuple check_primary_key(void);
HeapTuple check_foreign_key(void);
typedef struct
{
char *ident;
int nplans;
void **splan;
} EPlan;
static EPlan *FPlans = NULL;
static int nFPlans = 0;
static EPlan *PPlans = NULL;
static int nPPlans = 0;
static EPlan *find_plan(char *ident, EPlan ** eplan, int *nplans);
/*
* check_primary_key () -- check that key in tuple being inserted/updated
* references existing tuple in "primary" table.
* Though it's called without args You have to specify referenced
* table/keys while creating trigger: key field names in triggered table,
* referenced table name, referenced key field names,type of action [automatic|dependent]:
* EXECUTE PROCEDURE
* check_primary_key ('Fkey1', 'Fkey2', 'Ptable', 'Pkey1', 'Pkey2','[automatic|dependent]').
*/
HeapTuple /* have to return HeapTuple to Executor */
check_primary_key()
{
Trigger *trigger; /* to get trigger name */
int nargs; /* # of args specified in CREATE TRIGGER */
char **args; /* arguments: column names and table name */
int nkeys; /* # of key columns (= (nargs-1) / 2) */
Datum *kvals; /* key values */
char *relname; /* referenced relation name */
char *action; /* action on insert or update*/
Relation rel; /* triggered relation */
HeapTuple tuple = NULL; /* tuple to return */
TupleDesc tupdesc; /* tuple description */
EPlan *plan; /* prepared plan */
Oid *argtypes = NULL;/* key types to prepare execution plan */
bool isnull; /* to know is some column NULL or not */
char ident[2 * NAMEDATALEN]; /* to identify myself */
int ret;
int i;
/*
* Some checks first...
*/
/* Called by trigger manager ? */
if (!CurrentTriggerData)
elog(ERROR, "check_primary_key: triggers are not initialized");
/* Should be called for ROW trigger */
if (TRIGGER_FIRED_FOR_STATEMENT(CurrentTriggerData->tg_event))
elog(ERROR, "check_primary_key: can't process STATEMENT events");
/* If INSERTion then must check Tuple to being inserted */
if (TRIGGER_FIRED_BY_INSERT(CurrentTriggerData->tg_event))
tuple = CurrentTriggerData->tg_trigtuple;
/* Not should be called for DELETE */
else if (TRIGGER_FIRED_BY_DELETE(CurrentTriggerData->tg_event))
elog(ERROR, "check_primary_key: can't process DELETE events");
/* If UPDATion the must check new Tuple, not old one */
else
tuple = CurrentTriggerData->tg_newtuple;
trigger = CurrentTriggerData->tg_trigger;
nargs = trigger->tgnargs;
args = trigger->tgargs;
if ((nargs-1) % 2 != 1) /* odd number of arguments! */
elog(ERROR, "check_primary_key: even number of arguments should be specified");
nkeys = (nargs-1) / 2;
action=args[nargs -1];
if (strcmp(action,"automatic") && strcmp(action,"dependent"))
elog(ERROR,"check_primary_key: unknown action");
nargs=nargs-1;
relname = args[nkeys];
rel = CurrentTriggerData->tg_relation;
tupdesc = rel->rd_att;
/*
* Setting CurrentTriggerData to NULL prevents direct calls to trigger
* functions in queries. Normally, trigger functions have to be called
* by trigger manager code only.
*/
CurrentTriggerData = NULL;
/* Connect to SPI manager */
if ((ret = SPI_connect()) < 0)
elog(ERROR, "check_primary_key: SPI_connect returned %d", ret);
/*
* We use SPI plan preparation feature, so allocate space to place key
* values.
*/
kvals = (Datum *) palloc(nkeys * sizeof(Datum));
/*
* Construct ident string as TriggerName $ TriggeredRelationId and try
* to find prepared execution plan.
*/
sprintf(ident, "%s$%u", trigger->tgname, rel->rd_id);
plan = find_plan(ident, &PPlans, &nPPlans);
/* if there is no plan then allocate argtypes for preparation */
if (plan->nplans <= 0)
argtypes = (Oid *) palloc(nkeys * sizeof(Oid));
/* For each column in key ... */
for (i = 0; i < nkeys; i++)
{
/* get index of column in tuple */
int fnumber = SPI_fnumber(tupdesc, args[i]);
/* Bad guys may give us un-existing column in CREATE TRIGGER */
if (fnumber < 0)
elog(ERROR, "check_primary_key: there is no attribute %s in relation %s",
args[i], SPI_getrelname(rel));
/* Well, get binary (in internal format) value of column */
kvals[i] = SPI_getbinval(tuple, tupdesc, fnumber, &isnull);
/*
* If it's NULL then nothing to do! DON'T FORGET call SPI_finish
* ()! DON'T FORGET return tuple! Executor inserts tuple you're
* returning! If you return NULL then nothing will be inserted!
*/
if (isnull)
{
SPI_finish();
return (tuple);
}
if (plan->nplans <= 0) /* Get typeId of column */
argtypes[i] = SPI_gettypeid(tupdesc, fnumber);
}
/*
* If we have to prepare plan ...
*/
if (plan->nplans <= 0)
{
void *pplan;
char sql[8192];
/*
* Construct query: SELECT 1 FROM _referenced_relation_ WHERE
* Pkey1 = $1 [AND Pkey2 = $2 [...]]
*/
sprintf(sql, "select 1 from %s where ", relname);
for (i = 0; i < nkeys; i++)
{
sprintf(sql + strlen(sql), "%s = $%d %s",
args[i + nkeys + 1], i + 1, (i < nkeys - 1) ? "and " : "");
}
/* Prepare plan for query */
pplan = SPI_prepare(sql, nkeys, argtypes);
if (pplan == NULL)
elog(ERROR, "check_primary_key: SPI_prepare returned %d", SPI_result);
/*
* Remember that SPI_prepare places plan in current memory context
* - so, we have to save plan in Top memory context for latter
* use.
*/
pplan = SPI_saveplan(pplan);
if (pplan == NULL)
elog(ERROR, "check_primary_key: SPI_saveplan returned %d", SPI_result);
plan->splan = (void **) malloc(sizeof(void *));
*(plan->splan) = pplan;
plan->nplans = 1;
}
/*
* Ok, execute prepared plan.
*/
ret = SPI_execp(*(plan->splan), kvals, NULL, 1);
/* we have no NULLs - so we pass ^^^^ here */
if (ret < 0)
elog(ERROR, "check_primary_key: SPI_execp returned %d", ret);
/*
* If there are no tuples returned by SELECT then ...
*/
if (SPI_processed == 0 && strcmp(action,"dependent")==0)
elog(ERROR, "%s: tuple references non-existing key in %s",
trigger->tgname, relname);
else if (strcmp(action,"automatic")==0)
{
/* insert tuple in parent with only primary keys */
/* prepare plan */
void *pplan;
char sql[8192];
/*
* Construct query:INSERT INTO relname (Pkey1[,Pkey2]*) values ($1,$2..);
*/
sprintf(sql, "insert into %s ( ", relname);
for (i = 0; i < nkeys; i++)
{
sprintf(sql + strlen(sql), "%s%s ", args[i + nkeys + 1],(i<nkeys-1) ? ",":"");
}
sprintf(sql+strlen(sql),") values (");
for (i=0;i<nkeys; i++)
{
sprintf(sql+strlen(sql),"$%d%s ",i+1,(i<nkeys-1) ? ",":"");
}
sprintf(sql+strlen(sql),")");
/* Prepare plan for query */
pplan = SPI_prepare(sql, nkeys, argtypes);
if (pplan == NULL)
elog(ERROR, "check_primary_key: SPI_prepare returned %d", SPI_result);
/*
* Remember that SPI_prepare places plan in current memory context
* - so, we have to save plan in Top memory context for latter
* use.
*/
pplan = SPI_saveplan(pplan);
if (pplan == NULL)
elog(ERROR, "check_primary_key: SPI_saveplan returned %d", SPI_result);
plan->splan = (void **) malloc(sizeof(void *));
*(plan->splan) = pplan;
plan->nplans = 1;
/*
* Ok, execute prepared plan.
*/
ret = SPI_execp(*(plan->splan), kvals, NULL, 1);
/* we have no NULLs - so we pass ^^^^ here */
if (ret < 0)
elog(ERROR, "check_primary_key: SPI_execp returned %d", ret);
/*
* If there are no tuples returned by INSERT then ...
*/
if (SPI_processed == 0)
elog(ERROR, "error: can't enter automatically in %s",relname);
}
SPI_finish();
return (tuple);
}
/*
* check_foreign_key () -- check that key in tuple being deleted/updated
* is not referenced by tuples in "foreign" table(s).
* Though it's called without args You have to specify (while creating trigger):
* number of references, action to do if key referenced
* ('restrict' | 'setnull' | 'cascade'), key field names in triggered
* ("primary") table and referencing table(s)/keys:
* EXECUTE PROCEDURE
* check_foreign_key (2, 'restrict', 'Pkey1', 'Pkey2',
* 'Ftable1', 'Fkey11', 'Fkey12', 'Ftable2', 'Fkey21', 'Fkey22').
*/
HeapTuple /* have to return HeapTuple to Executor */
check_foreign_key()
{
Trigger *trigger; /* to get trigger name */
int nargs; /* # of args specified in CREATE TRIGGER */
char **args; /* arguments: as described above */
int nrefs; /* number of references (== # of plans) */
char action; /* 'R'estrict | 'S'etnull | 'C'ascade */
int nkeys; /* # of key columns */
Datum *kvals; /* key values */
char *relname; /* referencing relation name */
Relation rel; /* triggered relation */
HeapTuple trigtuple = NULL; /* tuple to being changed */
HeapTuple newtuple = NULL;/* tuple to return */
TupleDesc tupdesc; /* tuple description */
EPlan *plan; /* prepared plan(s) */
Oid *argtypes = NULL;/* key types to prepare execution plan */
bool isnull; /* to know is some column NULL or not */
bool isequal = true; /* are keys in both tuples equal (in
* UPDATE) */
char ident[2 * NAMEDATALEN]; /* to identify myself */
int ret;
int i,
r;
/*
* Some checks first...
*/
/* Called by trigger manager ? */
if (!CurrentTriggerData)
elog(ERROR, "check_foreign_key: triggers are not initialized");
/* Should be called for ROW trigger */
if (TRIGGER_FIRED_FOR_STATEMENT(CurrentTriggerData->tg_event))
elog(ERROR, "check_foreign_key: can't process STATEMENT events");
/* Not should be called for INSERT */
if (TRIGGER_FIRED_BY_INSERT(CurrentTriggerData->tg_event))
elog(ERROR, "check_foreign_key: can't process INSERT events");
/* Have to check tg_trigtuple - tuple being deleted */
trigtuple = CurrentTriggerData->tg_trigtuple;
/*
* But if this is UPDATE then we have to return tg_newtuple. Also, if
* key in tg_newtuple is the same as in tg_trigtuple then nothing to
* do.
*/
if (TRIGGER_FIRED_BY_UPDATE(CurrentTriggerData->tg_event))
newtuple = CurrentTriggerData->tg_newtuple;
trigger = CurrentTriggerData->tg_trigger;
nargs = trigger->tgnargs;
args = trigger->tgargs;
if (nargs < 5) /* nrefs, action, key, Relation, key - at
* least */
elog(ERROR, "check_foreign_key: too short %d (< 5) list of arguments", nargs);
nrefs = pg_atoi(args[0], sizeof(int), 0);
if (nrefs < 1)
elog(ERROR, "check_foreign_key: %d (< 1) number of references specified", nrefs);
action = tolower(*(args[1]));
if (action != 'r' && action != 'c' && action != 's')
elog(ERROR, "check_foreign_key: invalid action %s", args[1]);
nargs -= 2;
args += 2;
nkeys = (nargs - nrefs) / (nrefs + 1);
if (nkeys <= 0 || nargs != (nrefs + nkeys * (nrefs + 1)))
elog(ERROR, "check_foreign_key: invalid number of arguments %d for %d references",
nargs + 2, nrefs);
rel = CurrentTriggerData->tg_relation;
tupdesc = rel->rd_att;
/*
* Setting CurrentTriggerData to NULL prevents direct calls to trigger
* functions in queries. Normally, trigger functions have to be called
* by trigger manager code only.
*/
CurrentTriggerData = NULL;
/* Connect to SPI manager */
if ((ret = SPI_connect()) < 0)
elog(ERROR, "check_foreign_key: SPI_connect returned %d", ret);
/*
* We use SPI plan preparation feature, so allocate space to place key
* values.
*/
kvals = (Datum *) palloc(nkeys * sizeof(Datum));
/*
* Construct ident string as TriggerName $ TriggeredRelationId and try
* to find prepared execution plan(s).
*/
sprintf(ident, "%s$%u", trigger->tgname, rel->rd_id);
plan = find_plan(ident, &FPlans, &nFPlans);
/* if there is no plan(s) then allocate argtypes for preparation */
if (plan->nplans <= 0)
argtypes = (Oid *) palloc(nkeys * sizeof(Oid));
/*
* else - check that we have exactly nrefs plan(s) ready
*/
else if (plan->nplans != nrefs)
elog(ERROR, "%s: check_foreign_key: # of plans changed in meantime",
trigger->tgname);
/* For each column in key ... */
for (i = 0; i < nkeys; i++)
{
/* get index of column in tuple */
int fnumber = SPI_fnumber(tupdesc, args[i]);
/* Bad guys may give us un-existing column in CREATE TRIGGER */
if (fnumber < 0)
elog(ERROR, "check_foreign_key: there is no attribute %s in relation %s",
args[i], SPI_getrelname(rel));
/* Well, get binary (in internal format) value of column */
kvals[i] = SPI_getbinval(trigtuple, tupdesc, fnumber, &isnull);
/*
* If it's NULL then nothing to do! DON'T FORGET call SPI_finish
* ()! DON'T FORGET return tuple! Executor inserts tuple you're
* returning! If you return NULL then nothing will be inserted!
*/
if (isnull)
{
SPI_finish();
return ((newtuple == NULL) ? trigtuple : newtuple);
}
/*
* If UPDATE then get column value from new tuple being inserted
* and compare is this the same as old one. For the moment we use
* string presentation of values...
*/
if (newtuple != NULL)
{
char *oldval = SPI_getvalue(trigtuple, tupdesc, fnumber);
char *newval;
/* this shouldn't happen! SPI_ERROR_NOOUTFUNC ? */
if (oldval == NULL)
elog(ERROR, "check_foreign_key: SPI_getvalue returned %d", SPI_result);
newval = SPI_getvalue(newtuple, tupdesc, fnumber);
if (newval == NULL || strcmp(oldval, newval) != 0)
isequal = false;
}
if (plan->nplans <= 0) /* Get typeId of column */
argtypes[i] = SPI_gettypeid(tupdesc, fnumber);
}
nargs -= nkeys;
args += nkeys;
/*
* If we have to prepare plans ...
*/
if (plan->nplans <= 0)
{
void *pplan;
char sql[8192];
char **args2 = args;
plan->splan = (void **) malloc(nrefs * sizeof(void *));
for (r = 0; r < nrefs; r++)
{
relname = args2[0];
/*
* For 'R'estrict action we construct SELECT query - SELECT 1
* FROM _referencing_relation_ WHERE Fkey1 = $1 [AND Fkey2 =
* $2 [...]] - to check is tuple referenced or not.
*/
if (action == 'r')
sprintf(sql, "select 1 from %s where ", relname);
/*
* For 'C'ascade action we construct DELETE query - DELETE
* FROM _referencing_relation_ WHERE Fkey1 = $1 [AND Fkey2 =
* $2 [...]] - to delete all referencing tuples.
*/
else if (action == 'c')
sprintf(sql, "delete from %s where ", relname);
/*
* For 'S'etnull action we construct UPDATE query - UPDATE
* _referencing_relation_ SET Fkey1 null [, Fkey2 null [...]]
* WHERE Fkey1 = $1 [AND Fkey2 = $2 [...]] - to set key
* columns in all referencing tuples to NULL.
*/
else if (action == 's')
{
sprintf(sql, "update %s set ", relname);
for (i = 1; i <= nkeys; i++)
{
sprintf(sql + strlen(sql), "%s = null%s",
args2[i], (i < nkeys) ? ", " : "");
}
strcat(sql, " where ");
}
/* Construct WHERE qual */
for (i = 1; i <= nkeys; i++)
{
sprintf(sql + strlen(sql), "%s = $%d %s",
args2[i], i, (i < nkeys) ? "and " : "");
}
/* Prepare plan for query */
pplan = SPI_prepare(sql, nkeys, argtypes);
if (pplan == NULL)
elog(ERROR, "check_foreign_key: SPI_prepare returned %d", SPI_result);
/*
* Remember that SPI_prepare places plan in current memory
* context - so, we have to save plan in Top memory context
* for latter use.
*/
pplan = SPI_saveplan(pplan);
if (pplan == NULL)
elog(ERROR, "check_foreign_key: SPI_saveplan returned %d", SPI_result);
plan->splan[r] = pplan;
args2 += nkeys + 1; /* to the next relation */
}
plan->nplans = nrefs;
}
/*
* If UPDATE and key is not changed ...
*/
if (newtuple != NULL && isequal)
{
SPI_finish();
return (newtuple);
}
/*
* Ok, execute prepared plan(s).
*/
for (r = 0; r < nrefs; r++)
{
/*
* For 'R'estrict we may to execute plan for one tuple only, for
* other actions - for all tuples.
*/
int tcount = (action == 'r') ? 1 : 0;
relname = args[0];
ret = SPI_execp(plan->splan[r], kvals, NULL, tcount);
/* we have no NULLs - so we pass ^^^^ here */
if (ret < 0)
elog(ERROR, "check_foreign_key: SPI_execp returned %d", ret);
/* If action is 'R'estrict ... */
if (action == 'r')
{
/* If there is tuple returned by SELECT then ... */
if (SPI_processed > 0)
elog(ERROR, "%s: tuple referenced in %s",
trigger->tgname, relname);
}
#ifdef REFINT_VERBOSE
else
elog(NOTICE, "%s: %d tuple(s) of %s are %s",
trigger->tgname, SPI_processed, relname,
(action == 'c') ? "deleted" : "setted to null");
#endif
args += nkeys + 1; /* to the next relation */
}
SPI_finish();
return ((newtuple == NULL) ? trigtuple : newtuple);
}
static EPlan *
find_plan(char *ident, EPlan ** eplan, int *nplans)
{
EPlan *newp;
int i;
if (*nplans > 0)
{
for (i = 0; i < *nplans; i++)
{
if (strcmp((*eplan)[i].ident, ident) == 0)
break;
}
if (i != *nplans)
return (*eplan + i);
*eplan = (EPlan *) realloc(*eplan, (i + 1) * sizeof(EPlan));
newp = *eplan + i;
}
else
{
newp = *eplan = (EPlan *) malloc(sizeof(EPlan));
(*nplans) = i = 0;
}
newp->ident = (char *) malloc(strlen(ident) + 1);
strcpy(newp->ident, ident);
newp->nplans = 0;
newp->splan = NULL;
(*nplans)++;
return (newp);
}
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