refint.c

Go to the documentation of this file.

/*
 * contrib/spi/refint.c
 *
 *
 * refint.c --  set of functions to define referential integrity
 *      constraints using general triggers.
 */
#include "postgres.h"
 
#include <ctype.h>
 
#include "commands/trigger.h"
#include "executor/spi.h"
#include "utils/builtins.h"
#include "utils/memutils.h"
#include "utils/rel.h"
 
PG_MODULE_MAGIC_EXT(
                    .name = "refint",
                    .version = PG_VERSION
);
 
typedef struct
{
    char       *ident;
    int         nplans;
    SPIPlanPtr *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:
 * EXECUTE PROCEDURE
 * check_primary_key ('Fkey1', 'Fkey2', 'Ptable', 'Pkey1', 'Pkey2').
 */
 
PG_FUNCTION_INFO_V1(check_primary_key);
 
Datum
check_primary_key(PG_FUNCTION_ARGS)
{
    TriggerData *trigdata = (TriggerData *) fcinfo->context;
    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 / 2) */
    Datum      *kvals;          /* key values */
    char       *relname;        /* referenced relation name */
    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;
 
#ifdef  DEBUG_QUERY
    elog(DEBUG4, "check_primary_key: Enter Function");
#endif
 
    /*
     * Some checks first...
     */
 
    /* Called by trigger manager ? */
    if (!CALLED_AS_TRIGGER(fcinfo))
        /* internal error */
        elog(ERROR, "check_primary_key: not fired by trigger manager");
 
    /* Should be called for ROW trigger */
    if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
        /* internal error */
        elog(ERROR, "check_primary_key: must be fired for row");
 
    if (!TRIGGER_FIRED_AFTER(trigdata->tg_event))
        /* internal error */
        elog(ERROR, "check_primary_key: must be fired by AFTER trigger");
 
    /* If INSERTion then must check Tuple to being inserted */
    if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
        tuple = trigdata->tg_trigtuple;
 
    /* Not should be called for DELETE */
    else if (TRIGGER_FIRED_BY_DELETE(trigdata->tg_event))
        /* internal error */
        elog(ERROR, "check_primary_key: cannot process DELETE events");
 
    /* If UPDATE, then must check new Tuple, not old one */
    else
        tuple = trigdata->tg_newtuple;
 
    trigger = trigdata->tg_trigger;
    nargs = trigger->tgnargs;
    args = trigger->tgargs;
 
    if (nargs % 2 != 1)         /* odd number of arguments! */
        /* internal error */
        elog(ERROR, "check_primary_key: odd number of arguments should be specified");
 
    nkeys = nargs / 2;
    relname = args[nkeys];
    rel = trigdata->tg_relation;
    tupdesc = rel->rd_att;
 
    /* Connect to SPI manager */
    SPI_connect();
 
    /*
     * 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.
     */
    snprintf(ident, sizeof(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)
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_COLUMN),
                     errmsg("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 PointerGetDatum(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)
    {
        SPIPlanPtr  pplan;
        StringInfoData sql;
 
        initStringInfo(&sql);
 
        /*
         * Construct query: SELECT 1 FROM _referenced_relation_ WHERE Pkey1 =
         * $1 [AND Pkey2 = $2 [...]]
         */
        appendStringInfo(&sql, "select 1 from %s where ", relname);
        for (i = 1; i <= nkeys; i++)
        {
            appendStringInfo(&sql, "%s = $%d ", args[i + nkeys], i);
            if (i < nkeys)
                appendStringInfoString(&sql, "and ");
        }
 
        /* Prepare plan for query */
        pplan = SPI_prepare(sql.data, nkeys, argtypes);
        if (pplan == NULL)
            /* internal error */
            elog(ERROR, "check_primary_key: SPI_prepare returned %s", SPI_result_code_string(SPI_result));
 
        /*
         * Remember that SPI_prepare places plan in current memory context -
         * so, we have to save plan in TopMemoryContext for later use.
         */
        if (SPI_keepplan(pplan))
            /* internal error */
            elog(ERROR, "check_primary_key: SPI_keepplan failed");
        plan->splan = (SPIPlanPtr *) MemoryContextAlloc(TopMemoryContext,
                                                        sizeof(SPIPlanPtr));
        *(plan->splan) = pplan;
        plan->nplans = 1;
 
        pfree(sql.data);
    }
 
    /*
     * Ok, execute prepared plan.
     */
    ret = SPI_execp(*(plan->splan), kvals, NULL, 1);
    /* we have no NULLs - so we pass   ^^^^   here */
 
    if (ret < 0)
        /* internal error */
        elog(ERROR, "check_primary_key: SPI_execp returned %d", ret);
 
    /*
     * If there are no tuples returned by SELECT then ...
     */
    if (SPI_processed == 0)
        ereport(ERROR,
                (errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
                 errmsg("tuple references non-existent key"),
                 errdetail("Trigger \"%s\" found tuple referencing non-existent key in \"%s\".", trigger->tgname, relname)));
 
    SPI_finish();
 
    return PointerGetDatum(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').
 */
 
PG_FUNCTION_INFO_V1(check_foreign_key);
 
Datum
check_foreign_key(PG_FUNCTION_ARGS)
{
    TriggerData *trigdata = (TriggerData *) fcinfo->context;
    Trigger    *trigger;        /* to get trigger name */
    int         nargs;          /* # of args specified in CREATE TRIGGER */
    char      **args;           /* arguments: as described above */
    char      **args_temp;
    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         is_update = 0;
    int         ret;
    int         i,
                r;
 
#ifdef DEBUG_QUERY
    elog(DEBUG4, "check_foreign_key: Enter Function");
#endif
 
    /*
     * Some checks first...
     */
 
    /* Called by trigger manager ? */
    if (!CALLED_AS_TRIGGER(fcinfo))
        /* internal error */
        elog(ERROR, "check_foreign_key: not fired by trigger manager");
 
    /* Should be called for ROW trigger */
    if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
        /* internal error */
        elog(ERROR, "check_foreign_key: must be fired for row");
 
    /* Not should be called for INSERT */
    if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
        /* internal error */
        elog(ERROR, "check_foreign_key: cannot process INSERT events");
 
    if (!TRIGGER_FIRED_AFTER(trigdata->tg_event))
        /* internal error */
        elog(ERROR, "check_foreign_key: must be fired by AFTER trigger");
 
    /* Have to check tg_trigtuple - tuple being deleted */
    trigtuple = trigdata->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.
     */
    is_update = 0;
    if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
    {
        newtuple = trigdata->tg_newtuple;
        is_update = 1;
    }
    trigger = trigdata->tg_trigger;
    nargs = trigger->tgnargs;
    args = trigger->tgargs;
 
    if (nargs < 5)              /* nrefs, action, key, Relation, key - at
                                 * least */
        /* internal error */
        elog(ERROR, "check_foreign_key: too short %d (< 5) list of arguments", nargs);
 
    nrefs = pg_strtoint32(args[0]);
    if (nrefs < 1)
        /* internal error */
        elog(ERROR, "check_foreign_key: %d (< 1) number of references specified", nrefs);
    action = pg_ascii_tolower((unsigned char) *(args[1]));
    if (action != 'r' && action != 'c' && action != 's')
        /* internal error */
        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)))
        /* internal error */
        elog(ERROR, "check_foreign_key: invalid number of arguments %d for %d references",
             nargs + 2, nrefs);
 
    rel = trigdata->tg_relation;
    tupdesc = rel->rd_att;
 
    /* Connect to SPI manager */
    SPI_connect();
 
    /*
     * 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 $
     * OperationType and try to find prepared execution plan(s).
     */
    snprintf(ident, sizeof(ident), "%s$%u$%c", trigger->tgname, rel->rd_id, is_update ? 'U' : 'D');
    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)
        /* internal error */
        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)
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_COLUMN),
                     errmsg("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 PointerGetDatum((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)
                /* internal error */
                elog(ERROR, "check_foreign_key: SPI_getvalue returned %s", SPI_result_code_string(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);
    }
    args_temp = args;
    nargs -= nkeys;
    args += nkeys;
 
    /*
     * If we have to prepare plans ...
     */
    if (plan->nplans <= 0)
    {
        SPIPlanPtr  pplan;
        char      **args2 = args;
 
        plan->splan = (SPIPlanPtr *) MemoryContextAlloc(TopMemoryContext,
                                                        nrefs * sizeof(SPIPlanPtr));
 
        for (r = 0; r < nrefs; r++)
        {
            StringInfoData sql;
 
            initStringInfo(&sql);
 
            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')
                appendStringInfo(&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.
             *---------
             */
 
            /*
             * Max : Cascade with UPDATE query i create update query that
             * updates new key values in referenced tables
             */
 
 
            else if (action == 'c')
            {
                if (is_update == 1)
                {
                    int         fn;
                    char       *nv;
                    int         k;
 
                    appendStringInfo(&sql, "update %s set ", relname);
                    for (k = 1; k <= nkeys; k++)
                    {
                        fn = SPI_fnumber(tupdesc, args_temp[k - 1]);
                        Assert(fn > 0); /* already checked above */
                        nv = SPI_getvalue(newtuple, tupdesc, fn);
 
                        appendStringInfo(&sql, " %s = %s ",
                                         args2[k],
                                         nv ? quote_literal_cstr(nv) : "NULL");
                        if (k < nkeys)
                            appendStringInfoString(&sql, ", ");
                    }
                    appendStringInfoString(&sql, " where ");
                }
                else
                    /* DELETE */
                    appendStringInfo(&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')
            {
                appendStringInfo(&sql, "update %s set ", relname);
                for (i = 1; i <= nkeys; i++)
                {
                    appendStringInfo(&sql, "%s = null", args2[i]);
                    if (i < nkeys)
                        appendStringInfoString(&sql, ", ");
                }
                appendStringInfoString(&sql, " where ");
            }
 
            /* Construct WHERE qual */
            for (i = 1; i <= nkeys; i++)
            {
                appendStringInfo(&sql, "%s = $%d ", args2[i], i);
                if (i < nkeys)
                    appendStringInfoString(&sql, "and ");
            }
 
            /* Prepare plan for query */
            pplan = SPI_prepare(sql.data, nkeys, argtypes);
            if (pplan == NULL)
                /* internal error */
                elog(ERROR, "check_foreign_key: SPI_prepare returned %s", SPI_result_code_string(SPI_result));
 
            /*
             * Remember that SPI_prepare places plan in current memory context
             * - so, we have to save plan in Top memory context for later use.
             */
            if (SPI_keepplan(pplan))
                /* internal error */
                elog(ERROR, "check_foreign_key: SPI_keepplan failed");
 
            plan->splan[r] = pplan;
 
            args2 += nkeys + 1; /* to the next relation */
 
#ifdef DEBUG_QUERY
            elog(DEBUG4, "check_foreign_key Debug Query is :  %s ", sql.data);
#endif
 
            pfree(sql.data);
        }
        plan->nplans = nrefs;
    }
 
    /*
     * If UPDATE and key is not changed ...
     */
    if (newtuple != NULL && isequal)
    {
        SPI_finish();
        return PointerGetDatum(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)
            ereport(ERROR,
                    (errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
                     errmsg("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)
                ereport(ERROR,
                        (errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
                         errmsg("\"%s\": tuple is referenced in \"%s\"",
                                trigger->tgname, relname)));
        }
        else
        {
#ifdef REFINT_VERBOSE
            const char *operation;
 
            if (action == 'c')
                operation = is_update ? "updated" : "deleted";
            else
                operation = "set to null";
 
            elog(NOTICE, "%s: " UINT64_FORMAT " tuple(s) of %s are %s",
                 trigger->tgname, SPI_processed, relname, operation);
#endif
        }
        args += nkeys + 1;      /* to the next relation */
    }
 
    SPI_finish();
 
    return PointerGetDatum((newtuple == NULL) ? trigtuple : newtuple);
}
 
static EPlan *
find_plan(char *ident, EPlan **eplan, int *nplans)
{
    EPlan      *newp;
    int         i;
    MemoryContext oldcontext;
 
    /*
     * All allocations done for the plans need to happen in a session-safe
     * context.
     */
    oldcontext = MemoryContextSwitchTo(TopMemoryContext);
 
    if (*nplans > 0)
    {
        for (i = 0; i < *nplans; i++)
        {
            if (strcmp((*eplan)[i].ident, ident) == 0)
                break;
        }
        if (i != *nplans)
        {
            MemoryContextSwitchTo(oldcontext);
            return (*eplan + i);
        }
        *eplan = (EPlan *) repalloc(*eplan, (i + 1) * sizeof(EPlan));
        newp = *eplan + i;
    }
    else
    {
        newp = *eplan = palloc_object(EPlan);
        (*nplans) = i = 0;
    }
 
    newp->ident = pstrdup(ident);
    newp->nplans = 0;
    newp->splan = NULL;
    (*nplans)++;
 
    MemoryContextSwitchTo(oldcontext);
    return newp;
}