pg_constraint.c

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/*-------------------------------------------------------------------------
 *
 * pg_constraint.c
 *    routines to support manipulation of the pg_constraint relation
 *
 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/catalog/pg_constraint.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "access/genam.h"
#include "access/htup_details.h"
#include "access/sysattr.h"
#include "access/table.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/dependency.h"
#include "catalog/heap.h"
#include "catalog/indexing.h"
#include "catalog/objectaccess.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_type.h"
#include "commands/defrem.h"
#include "commands/tablecmds.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/syscache.h"
 
 
/*
 * CreateConstraintEntry
 *  Create a constraint table entry.
 *
 * Subsidiary records (such as triggers or indexes to implement the
 * constraint) are *not* created here.  But we do make dependency links
 * from the constraint to the things it depends on.
 *
 * The new constraint's OID is returned.
 */
Oid
CreateConstraintEntry(const char *constraintName,
                      Oid constraintNamespace,
                      char constraintType,
                      bool isDeferrable,
                      bool isDeferred,
                      bool isValidated,
                      Oid parentConstrId,
                      Oid relId,
                      const int16 *constraintKey,
                      int constraintNKeys,
                      int constraintNTotalKeys,
                      Oid domainId,
                      Oid indexRelId,
                      Oid foreignRelId,
                      const int16 *foreignKey,
                      const Oid *pfEqOp,
                      const Oid *ppEqOp,
                      const Oid *ffEqOp,
                      int foreignNKeys,
                      char foreignUpdateType,
                      char foreignDeleteType,
                      const int16 *fkDeleteSetCols,
                      int numFkDeleteSetCols,
                      char foreignMatchType,
                      const Oid *exclOp,
                      Node *conExpr,
                      const char *conBin,
                      bool conIsLocal,
                      int conInhCount,
                      bool conNoInherit,
                      bool is_internal)
{
    Relation    conDesc;
    Oid         conOid;
    HeapTuple   tup;
    bool        nulls[Natts_pg_constraint];
    Datum       values[Natts_pg_constraint];
    ArrayType  *conkeyArray;
    ArrayType  *confkeyArray;
    ArrayType  *conpfeqopArray;
    ArrayType  *conppeqopArray;
    ArrayType  *conffeqopArray;
    ArrayType  *conexclopArray;
    ArrayType  *confdelsetcolsArray;
    NameData    cname;
    int         i;
    ObjectAddress conobject;
    ObjectAddresses *addrs_auto;
    ObjectAddresses *addrs_normal;
 
    conDesc = table_open(ConstraintRelationId, RowExclusiveLock);
 
    Assert(constraintName);
    namestrcpy(&cname, constraintName);
 
    /*
     * Convert C arrays into Postgres arrays.
     */
    if (constraintNKeys > 0)
    {
        Datum      *conkey;
 
        conkey = (Datum *) palloc(constraintNKeys * sizeof(Datum));
        for (i = 0; i < constraintNKeys; i++)
            conkey[i] = Int16GetDatum(constraintKey[i]);
        conkeyArray = construct_array_builtin(conkey, constraintNKeys, INT2OID);
    }
    else
        conkeyArray = NULL;
 
    if (foreignNKeys > 0)
    {
        Datum      *fkdatums;
 
        fkdatums = (Datum *) palloc(foreignNKeys * sizeof(Datum));
        for (i = 0; i < foreignNKeys; i++)
            fkdatums[i] = Int16GetDatum(foreignKey[i]);
        confkeyArray = construct_array_builtin(fkdatums, foreignNKeys, INT2OID);
        for (i = 0; i < foreignNKeys; i++)
            fkdatums[i] = ObjectIdGetDatum(pfEqOp[i]);
        conpfeqopArray = construct_array_builtin(fkdatums, foreignNKeys, OIDOID);
        for (i = 0; i < foreignNKeys; i++)
            fkdatums[i] = ObjectIdGetDatum(ppEqOp[i]);
        conppeqopArray = construct_array_builtin(fkdatums, foreignNKeys, OIDOID);
        for (i = 0; i < foreignNKeys; i++)
            fkdatums[i] = ObjectIdGetDatum(ffEqOp[i]);
        conffeqopArray = construct_array_builtin(fkdatums, foreignNKeys, OIDOID);
 
        if (numFkDeleteSetCols > 0)
        {
            for (i = 0; i < numFkDeleteSetCols; i++)
                fkdatums[i] = Int16GetDatum(fkDeleteSetCols[i]);
            confdelsetcolsArray = construct_array_builtin(fkdatums, numFkDeleteSetCols, INT2OID);
        }
        else
            confdelsetcolsArray = NULL;
    }
    else
    {
        confkeyArray = NULL;
        conpfeqopArray = NULL;
        conppeqopArray = NULL;
        conffeqopArray = NULL;
        confdelsetcolsArray = NULL;
    }
 
    if (exclOp != NULL)
    {
        Datum      *opdatums;
 
        opdatums = (Datum *) palloc(constraintNKeys * sizeof(Datum));
        for (i = 0; i < constraintNKeys; i++)
            opdatums[i] = ObjectIdGetDatum(exclOp[i]);
        conexclopArray = construct_array_builtin(opdatums, constraintNKeys, OIDOID);
    }
    else
        conexclopArray = NULL;
 
    /* initialize nulls and values */
    for (i = 0; i < Natts_pg_constraint; i++)
    {
        nulls[i] = false;
        values[i] = (Datum) NULL;
    }
 
    conOid = GetNewOidWithIndex(conDesc, ConstraintOidIndexId,
                                Anum_pg_constraint_oid);
    values[Anum_pg_constraint_oid - 1] = ObjectIdGetDatum(conOid);
    values[Anum_pg_constraint_conname - 1] = NameGetDatum(&cname);
    values[Anum_pg_constraint_connamespace - 1] = ObjectIdGetDatum(constraintNamespace);
    values[Anum_pg_constraint_contype - 1] = CharGetDatum(constraintType);
    values[Anum_pg_constraint_condeferrable - 1] = BoolGetDatum(isDeferrable);
    values[Anum_pg_constraint_condeferred - 1] = BoolGetDatum(isDeferred);
    values[Anum_pg_constraint_convalidated - 1] = BoolGetDatum(isValidated);
    values[Anum_pg_constraint_conrelid - 1] = ObjectIdGetDatum(relId);
    values[Anum_pg_constraint_contypid - 1] = ObjectIdGetDatum(domainId);
    values[Anum_pg_constraint_conindid - 1] = ObjectIdGetDatum(indexRelId);
    values[Anum_pg_constraint_conparentid - 1] = ObjectIdGetDatum(parentConstrId);
    values[Anum_pg_constraint_confrelid - 1] = ObjectIdGetDatum(foreignRelId);
    values[Anum_pg_constraint_confupdtype - 1] = CharGetDatum(foreignUpdateType);
    values[Anum_pg_constraint_confdeltype - 1] = CharGetDatum(foreignDeleteType);
    values[Anum_pg_constraint_confmatchtype - 1] = CharGetDatum(foreignMatchType);
    values[Anum_pg_constraint_conislocal - 1] = BoolGetDatum(conIsLocal);
    values[Anum_pg_constraint_coninhcount - 1] = Int16GetDatum(conInhCount);
    values[Anum_pg_constraint_connoinherit - 1] = BoolGetDatum(conNoInherit);
 
    if (conkeyArray)
        values[Anum_pg_constraint_conkey - 1] = PointerGetDatum(conkeyArray);
    else
        nulls[Anum_pg_constraint_conkey - 1] = true;
 
    if (confkeyArray)
        values[Anum_pg_constraint_confkey - 1] = PointerGetDatum(confkeyArray);
    else
        nulls[Anum_pg_constraint_confkey - 1] = true;
 
    if (conpfeqopArray)
        values[Anum_pg_constraint_conpfeqop - 1] = PointerGetDatum(conpfeqopArray);
    else
        nulls[Anum_pg_constraint_conpfeqop - 1] = true;
 
    if (conppeqopArray)
        values[Anum_pg_constraint_conppeqop - 1] = PointerGetDatum(conppeqopArray);
    else
        nulls[Anum_pg_constraint_conppeqop - 1] = true;
 
    if (conffeqopArray)
        values[Anum_pg_constraint_conffeqop - 1] = PointerGetDatum(conffeqopArray);
    else
        nulls[Anum_pg_constraint_conffeqop - 1] = true;
 
    if (confdelsetcolsArray)
        values[Anum_pg_constraint_confdelsetcols - 1] = PointerGetDatum(confdelsetcolsArray);
    else
        nulls[Anum_pg_constraint_confdelsetcols - 1] = true;
 
    if (conexclopArray)
        values[Anum_pg_constraint_conexclop - 1] = PointerGetDatum(conexclopArray);
    else
        nulls[Anum_pg_constraint_conexclop - 1] = true;
 
    if (conBin)
        values[Anum_pg_constraint_conbin - 1] = CStringGetTextDatum(conBin);
    else
        nulls[Anum_pg_constraint_conbin - 1] = true;
 
    tup = heap_form_tuple(RelationGetDescr(conDesc), values, nulls);
 
    CatalogTupleInsert(conDesc, tup);
 
    ObjectAddressSet(conobject, ConstraintRelationId, conOid);
 
    table_close(conDesc, RowExclusiveLock);
 
    /* Handle set of auto dependencies */
    addrs_auto = new_object_addresses();
 
    if (OidIsValid(relId))
    {
        /*
         * Register auto dependency from constraint to owning relation, or to
         * specific column(s) if any are mentioned.
         */
        ObjectAddress relobject;
 
        if (constraintNTotalKeys > 0)
        {
            for (i = 0; i < constraintNTotalKeys; i++)
            {
                ObjectAddressSubSet(relobject, RelationRelationId, relId,
                                    constraintKey[i]);
                add_exact_object_address(&relobject, addrs_auto);
            }
        }
        else
        {
            ObjectAddressSet(relobject, RelationRelationId, relId);
            add_exact_object_address(&relobject, addrs_auto);
        }
    }
 
    if (OidIsValid(domainId))
    {
        /*
         * Register auto dependency from constraint to owning domain
         */
        ObjectAddress domobject;
 
        ObjectAddressSet(domobject, TypeRelationId, domainId);
        add_exact_object_address(&domobject, addrs_auto);
    }
 
    record_object_address_dependencies(&conobject, addrs_auto,
                                       DEPENDENCY_AUTO);
    free_object_addresses(addrs_auto);
 
    /* Handle set of normal dependencies */
    addrs_normal = new_object_addresses();
 
    if (OidIsValid(foreignRelId))
    {
        /*
         * Register normal dependency from constraint to foreign relation, or
         * to specific column(s) if any are mentioned.
         */
        ObjectAddress relobject;
 
        if (foreignNKeys > 0)
        {
            for (i = 0; i < foreignNKeys; i++)
            {
                ObjectAddressSubSet(relobject, RelationRelationId,
                                    foreignRelId, foreignKey[i]);
                add_exact_object_address(&relobject, addrs_normal);
            }
        }
        else
        {
            ObjectAddressSet(relobject, RelationRelationId, foreignRelId);
            add_exact_object_address(&relobject, addrs_normal);
        }
    }
 
    if (OidIsValid(indexRelId) && constraintType == CONSTRAINT_FOREIGN)
    {
        /*
         * Register normal dependency on the unique index that supports a
         * foreign-key constraint.  (Note: for indexes associated with unique
         * or primary-key constraints, the dependency runs the other way, and
         * is not made here.)
         */
        ObjectAddress relobject;
 
        ObjectAddressSet(relobject, RelationRelationId, indexRelId);
        add_exact_object_address(&relobject, addrs_normal);
    }
 
    if (foreignNKeys > 0)
    {
        /*
         * Register normal dependencies on the equality operators that support
         * a foreign-key constraint.  If the PK and FK types are the same then
         * all three operators for a column are the same; otherwise they are
         * different.
         */
        ObjectAddress oprobject;
 
        oprobject.classId = OperatorRelationId;
        oprobject.objectSubId = 0;
 
        for (i = 0; i < foreignNKeys; i++)
        {
            oprobject.objectId = pfEqOp[i];
            add_exact_object_address(&oprobject, addrs_normal);
            if (ppEqOp[i] != pfEqOp[i])
            {
                oprobject.objectId = ppEqOp[i];
                add_exact_object_address(&oprobject, addrs_normal);
            }
            if (ffEqOp[i] != pfEqOp[i])
            {
                oprobject.objectId = ffEqOp[i];
                add_exact_object_address(&oprobject, addrs_normal);
            }
        }
    }
 
    record_object_address_dependencies(&conobject, addrs_normal,
                                       DEPENDENCY_NORMAL);
    free_object_addresses(addrs_normal);
 
    /*
     * We don't bother to register dependencies on the exclusion operators of
     * an exclusion constraint.  We assume they are members of the opclass
     * supporting the index, so there's an indirect dependency via that. (This
     * would be pretty dicey for cross-type operators, but exclusion operators
     * can never be cross-type.)
     */
 
    if (conExpr != NULL)
    {
        /*
         * Register dependencies from constraint to objects mentioned in CHECK
         * expression.
         */
        recordDependencyOnSingleRelExpr(&conobject, conExpr, relId,
                                        DEPENDENCY_NORMAL,
                                        DEPENDENCY_NORMAL, false);
    }
 
    /* Post creation hook for new constraint */
    InvokeObjectPostCreateHookArg(ConstraintRelationId, conOid, 0,
                                  is_internal);
 
    return conOid;
}
 
/*
 * Test whether given name is currently used as a constraint name
 * for the given object (relation or domain).
 *
 * This is used to decide whether to accept a user-specified constraint name.
 * It is deliberately not the same test as ChooseConstraintName uses to decide
 * whether an auto-generated name is OK: here, we will allow it unless there
 * is an identical constraint name in use *on the same object*.
 *
 * NB: Caller should hold exclusive lock on the given object, else
 * this test can be fooled by concurrent additions.
 */
bool
ConstraintNameIsUsed(ConstraintCategory conCat, Oid objId,
                     const char *conname)
{
    bool        found;
    Relation    conDesc;
    SysScanDesc conscan;
    ScanKeyData skey[3];
 
    conDesc = table_open(ConstraintRelationId, AccessShareLock);
 
    ScanKeyInit(&skey[0],
                Anum_pg_constraint_conrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum((conCat == CONSTRAINT_RELATION)
                                 ? objId : InvalidOid));
    ScanKeyInit(&skey[1],
                Anum_pg_constraint_contypid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum((conCat == CONSTRAINT_DOMAIN)
                                 ? objId : InvalidOid));
    ScanKeyInit(&skey[2],
                Anum_pg_constraint_conname,
                BTEqualStrategyNumber, F_NAMEEQ,
                CStringGetDatum(conname));
 
    conscan = systable_beginscan(conDesc, ConstraintRelidTypidNameIndexId,
                                 true, NULL, 3, skey);
 
    /* There can be at most one matching row */
    found = (HeapTupleIsValid(systable_getnext(conscan)));
 
    systable_endscan(conscan);
    table_close(conDesc, AccessShareLock);
 
    return found;
}
 
/*
 * Does any constraint of the given name exist in the given namespace?
 *
 * This is used for code that wants to match ChooseConstraintName's rule
 * that we should avoid autogenerating duplicate constraint names within a
 * namespace.
 */
bool
ConstraintNameExists(const char *conname, Oid namespaceid)
{
    bool        found;
    Relation    conDesc;
    SysScanDesc conscan;
    ScanKeyData skey[2];
 
    conDesc = table_open(ConstraintRelationId, AccessShareLock);
 
    ScanKeyInit(&skey[0],
                Anum_pg_constraint_conname,
                BTEqualStrategyNumber, F_NAMEEQ,
                CStringGetDatum(conname));
 
    ScanKeyInit(&skey[1],
                Anum_pg_constraint_connamespace,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(namespaceid));
 
    conscan = systable_beginscan(conDesc, ConstraintNameNspIndexId, true,
                                 NULL, 2, skey);
 
    found = (HeapTupleIsValid(systable_getnext(conscan)));
 
    systable_endscan(conscan);
    table_close(conDesc, AccessShareLock);
 
    return found;
}
 
/*
 * Select a nonconflicting name for a new constraint.
 *
 * The objective here is to choose a name that is unique within the
 * specified namespace.  Postgres does not require this, but the SQL
 * spec does, and some apps depend on it.  Therefore we avoid choosing
 * default names that so conflict.
 *
 * name1, name2, and label are used the same way as for makeObjectName(),
 * except that the label can't be NULL; digits will be appended to the label
 * if needed to create a name that is unique within the specified namespace.
 *
 * 'others' can be a list of string names already chosen within the current
 * command (but not yet reflected into the catalogs); we will not choose
 * a duplicate of one of these either.
 *
 * Note: it is theoretically possible to get a collision anyway, if someone
 * else chooses the same name concurrently.  This is fairly unlikely to be
 * a problem in practice, especially if one is holding an exclusive lock on
 * the relation identified by name1.
 *
 * Returns a palloc'd string.
 */
char *
ChooseConstraintName(const char *name1, const char *name2,
                     const char *label, Oid namespaceid,
                     List *others)
{
    int         pass = 0;
    char       *conname = NULL;
    char        modlabel[NAMEDATALEN];
    Relation    conDesc;
    SysScanDesc conscan;
    ScanKeyData skey[2];
    bool        found;
    ListCell   *l;
 
    conDesc = table_open(ConstraintRelationId, AccessShareLock);
 
    /* try the unmodified label first */
    strlcpy(modlabel, label, sizeof(modlabel));
 
    for (;;)
    {
        conname = makeObjectName(name1, name2, modlabel);
 
        found = false;
 
        foreach(l, others)
        {
            if (strcmp((char *) lfirst(l), conname) == 0)
            {
                found = true;
                break;
            }
        }
 
        if (!found)
        {
            ScanKeyInit(&skey[0],
                        Anum_pg_constraint_conname,
                        BTEqualStrategyNumber, F_NAMEEQ,
                        CStringGetDatum(conname));
 
            ScanKeyInit(&skey[1],
                        Anum_pg_constraint_connamespace,
                        BTEqualStrategyNumber, F_OIDEQ,
                        ObjectIdGetDatum(namespaceid));
 
            conscan = systable_beginscan(conDesc, ConstraintNameNspIndexId, true,
                                         NULL, 2, skey);
 
            found = (HeapTupleIsValid(systable_getnext(conscan)));
 
            systable_endscan(conscan);
        }
 
        if (!found)
            break;
 
        /* found a conflict, so try a new name component */
        pfree(conname);
        snprintf(modlabel, sizeof(modlabel), "%s%d", label, ++pass);
    }
 
    table_close(conDesc, AccessShareLock);
 
    return conname;
}
 
/*
 * Find and return the pg_constraint tuple that implements a validated
 * not-null constraint for the given column of the given relation.
 *
 * XXX This would be easier if we had pg_attribute.notnullconstr with the OID
 * of the constraint that implements the not-null constraint for that column.
 * I'm not sure it's worth the catalog bloat and de-normalization, however.
 */
HeapTuple
findNotNullConstraintAttnum(Oid relid, AttrNumber attnum)
{
    Relation    pg_constraint;
    HeapTuple   conTup,
                retval = NULL;
    SysScanDesc scan;
    ScanKeyData key;
 
    pg_constraint = table_open(ConstraintRelationId, AccessShareLock);
    ScanKeyInit(&key,
                Anum_pg_constraint_conrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(relid));
    scan = systable_beginscan(pg_constraint, ConstraintRelidTypidNameIndexId,
                              true, NULL, 1, &key);
 
    while (HeapTupleIsValid(conTup = systable_getnext(scan)))
    {
        Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(conTup);
        AttrNumber  conkey;
 
        /*
         * We're looking for a NOTNULL constraint that's marked validated,
         * with the column we're looking for as the sole element in conkey.
         */
        if (con->contype != CONSTRAINT_NOTNULL)
            continue;
        if (!con->convalidated)
            continue;
 
        conkey = extractNotNullColumn(conTup);
        if (conkey != attnum)
            continue;
 
        /* Found it */
        retval = heap_copytuple(conTup);
        break;
    }
 
    systable_endscan(scan);
    table_close(pg_constraint, AccessShareLock);
 
    return retval;
}
 
/*
 * Find and return the pg_constraint tuple that implements a validated
 * not-null constraint for the given column of the given relation.
 */
HeapTuple
findNotNullConstraint(Oid relid, const char *colname)
{
    AttrNumber  attnum = get_attnum(relid, colname);
 
    return findNotNullConstraintAttnum(relid, attnum);
}
 
/*
 * Given a pg_constraint tuple for a not-null constraint, return the column
 * number it is for.
 */
AttrNumber
extractNotNullColumn(HeapTuple constrTup)
{
    AttrNumber  colnum;
    Datum       adatum;
    ArrayType  *arr;
 
    /* only tuples for not-null constraints should be given */
    Assert(((Form_pg_constraint) GETSTRUCT(constrTup))->contype == CONSTRAINT_NOTNULL);
 
    adatum = SysCacheGetAttrNotNull(CONSTROID, constrTup,
                                    Anum_pg_constraint_conkey);
    arr = DatumGetArrayTypeP(adatum);   /* ensure not toasted */
    if (ARR_NDIM(arr) != 1 ||
        ARR_HASNULL(arr) ||
        ARR_ELEMTYPE(arr) != INT2OID ||
        ARR_DIMS(arr)[0] != 1)
        elog(ERROR, "conkey is not a 1-D smallint array");
 
    memcpy(&colnum, ARR_DATA_PTR(arr), sizeof(AttrNumber));
 
    if ((Pointer) arr != DatumGetPointer(adatum))
        pfree(arr);             /* free de-toasted copy, if any */
 
    return colnum;
}
 
/*
 * AdjustNotNullInheritance1
 *      Adjust inheritance count for a single not-null constraint
 *
 * Adjust inheritance count, and possibly islocal status, for the not-null
 * constraint row of the given column, if it exists, and return true.
 * If no not-null constraint is found for the column, return false.
 */
bool
AdjustNotNullInheritance1(Oid relid, AttrNumber attnum, int count,
                          bool is_no_inherit)
{
    HeapTuple   tup;
 
    tup = findNotNullConstraintAttnum(relid, attnum);
    if (HeapTupleIsValid(tup))
    {
        Relation    pg_constraint;
        Form_pg_constraint conform;
 
        pg_constraint = table_open(ConstraintRelationId, RowExclusiveLock);
        conform = (Form_pg_constraint) GETSTRUCT(tup);
 
        /*
         * Don't let the NO INHERIT status change (but don't complain
         * unnecessarily.)  In the future it might be useful to let an
         * inheritable constraint replace a non-inheritable one, but we'd need
         * to recurse to children to get it added there.
         */
        if (is_no_inherit != conform->connoinherit)
            ereport(ERROR,
                    errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                    errmsg("cannot change NO INHERIT status of inherited NOT NULL constraint \"%s\" on relation \"%s\"",
                           NameStr(conform->conname), get_rel_name(relid)));
 
        if (count > 0)
            conform->coninhcount += count;
 
        /* sanity check */
        if (conform->coninhcount < 0)
            elog(ERROR, "invalid inhcount %d for constraint \"%s\" on relation \"%s\"",
                 conform->coninhcount, NameStr(conform->conname),
                 get_rel_name(relid));
 
        /*
         * If the constraint is no longer inherited, mark it local.  It's
         * arguable that we should drop it instead, but it's hard to see that
         * being better.  The user can drop it manually later.
         */
        if (conform->coninhcount == 0)
            conform->conislocal = true;
 
        CatalogTupleUpdate(pg_constraint, &tup->t_self, tup);
 
        table_close(pg_constraint, RowExclusiveLock);
 
        return true;
    }
 
    return false;
}
 
/*
 * AdjustNotNullInheritance
 *      Adjust not-null constraints' inhcount/islocal for
 *      ALTER TABLE [NO] INHERITS
 *
 * Mark the NOT NULL constraints for the given relation columns as
 * inherited, so that they can't be dropped.
 *
 * Caller must have checked beforehand that attnotnull was set for all
 * columns.  However, some of those could be set because of a primary
 * key, so throw a proper user-visible error if one is not found.
 */
void
AdjustNotNullInheritance(Oid relid, Bitmapset *columns, int count)
{
    Relation    pg_constraint;
    int         attnum;
 
    pg_constraint = table_open(ConstraintRelationId, RowExclusiveLock);
 
    /*
     * Scan the set of columns and bump inhcount for each.
     */
    attnum = -1;
    while ((attnum = bms_next_member(columns, attnum)) >= 0)
    {
        HeapTuple   tup;
        Form_pg_constraint conform;
 
        tup = findNotNullConstraintAttnum(relid, attnum);
        if (!HeapTupleIsValid(tup))
            ereport(ERROR,
                    errcode(ERRCODE_DATATYPE_MISMATCH),
                    errmsg("column \"%s\" in child table must be marked NOT NULL",
                           get_attname(relid, attnum,
                                       false)));
 
        conform = (Form_pg_constraint) GETSTRUCT(tup);
        conform->coninhcount += count;
        if (conform->coninhcount < 0)
            elog(ERROR, "invalid inhcount %d for constraint \"%s\" on relation \"%s\"",
                 conform->coninhcount, NameStr(conform->conname),
                 get_rel_name(relid));
 
        /*
         * If the constraints are no longer inherited, mark them local.  It's
         * arguable that we should drop them instead, but it's hard to see
         * that being better.  The user can drop it manually later.
         */
        if (conform->coninhcount == 0)
            conform->conislocal = true;
 
        CatalogTupleUpdate(pg_constraint, &tup->t_self, tup);
    }
 
    table_close(pg_constraint, RowExclusiveLock);
}
 
/*
 * RelationGetNotNullConstraints
 *      Return the list of not-null constraints for the given rel
 *
 * Caller can request cooked constraints, or raw.
 *
 * This is seldom needed, so we just scan pg_constraint each time.
 *
 * XXX This is only used to create derived tables, so NO INHERIT constraints
 * are always skipped.
 */
List *
RelationGetNotNullConstraints(Oid relid, bool cooked)
{
    List       *notnulls = NIL;
    Relation    constrRel;
    HeapTuple   htup;
    SysScanDesc conscan;
    ScanKeyData skey;
 
    constrRel = table_open(ConstraintRelationId, AccessShareLock);
    ScanKeyInit(&skey,
                Anum_pg_constraint_conrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(relid));
    conscan = systable_beginscan(constrRel, ConstraintRelidTypidNameIndexId, true,
                                 NULL, 1, &skey);
 
    while (HeapTupleIsValid(htup = systable_getnext(conscan)))
    {
        Form_pg_constraint conForm = (Form_pg_constraint) GETSTRUCT(htup);
        AttrNumber  colnum;
 
        if (conForm->contype != CONSTRAINT_NOTNULL)
            continue;
        if (conForm->connoinherit)
            continue;
 
        colnum = extractNotNullColumn(htup);
 
        if (cooked)
        {
            CookedConstraint *cooked;
 
            cooked = (CookedConstraint *) palloc(sizeof(CookedConstraint));
 
            cooked->contype = CONSTR_NOTNULL;
            cooked->name = pstrdup(NameStr(conForm->conname));
            cooked->attnum = colnum;
            cooked->expr = NULL;
            cooked->skip_validation = false;
            cooked->is_local = true;
            cooked->inhcount = 0;
            cooked->is_no_inherit = conForm->connoinherit;
 
            notnulls = lappend(notnulls, cooked);
        }
        else
        {
            Constraint *constr;
 
            constr = makeNode(Constraint);
            constr->contype = CONSTR_NOTNULL;
            constr->conname = pstrdup(NameStr(conForm->conname));
            constr->deferrable = false;
            constr->initdeferred = false;
            constr->location = -1;
            constr->keys = list_make1(makeString(get_attname(relid, colnum,
                                                             false)));
            constr->skip_validation = false;
            constr->initially_valid = true;
            notnulls = lappend(notnulls, constr);
        }
    }
 
    systable_endscan(conscan);
    table_close(constrRel, AccessShareLock);
 
    return notnulls;
}
 
 
/*
 * Delete a single constraint record.
 */
void
RemoveConstraintById(Oid conId)
{
    Relation    conDesc;
    HeapTuple   tup;
    Form_pg_constraint con;
 
    conDesc = table_open(ConstraintRelationId, RowExclusiveLock);
 
    tup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(conId));
    if (!HeapTupleIsValid(tup)) /* should not happen */
        elog(ERROR, "cache lookup failed for constraint %u", conId);
    con = (Form_pg_constraint) GETSTRUCT(tup);
 
    /*
     * Special processing depending on what the constraint is for.
     */
    if (OidIsValid(con->conrelid))
    {
        Relation    rel;
 
        /*
         * If the constraint is for a relation, open and exclusive-lock the
         * relation it's for.
         */
        rel = table_open(con->conrelid, AccessExclusiveLock);
 
        /*
         * We need to update the relchecks count if it is a check constraint
         * being dropped.  This update will force backends to rebuild relcache
         * entries when we commit.
         */
        if (con->contype == CONSTRAINT_CHECK)
        {
            Relation    pgrel;
            HeapTuple   relTup;
            Form_pg_class classForm;
 
            pgrel = table_open(RelationRelationId, RowExclusiveLock);
            relTup = SearchSysCacheCopy1(RELOID,
                                         ObjectIdGetDatum(con->conrelid));
            if (!HeapTupleIsValid(relTup))
                elog(ERROR, "cache lookup failed for relation %u",
                     con->conrelid);
            classForm = (Form_pg_class) GETSTRUCT(relTup);
 
            if (classForm->relchecks == 0)  /* should not happen */
                elog(ERROR, "relation \"%s\" has relchecks = 0",
                     RelationGetRelationName(rel));
            classForm->relchecks--;
 
            CatalogTupleUpdate(pgrel, &relTup->t_self, relTup);
 
            heap_freetuple(relTup);
 
            table_close(pgrel, RowExclusiveLock);
        }
 
        /* Keep lock on constraint's rel until end of xact */
        table_close(rel, NoLock);
    }
    else if (OidIsValid(con->contypid))
    {
        /*
         * XXX for now, do nothing special when dropping a domain constraint
         *
         * Probably there should be some form of locking on the domain type,
         * but we have no such concept at the moment.
         */
    }
    else
        elog(ERROR, "constraint %u is not of a known type", conId);
 
    /* Fry the constraint itself */
    CatalogTupleDelete(conDesc, &tup->t_self);
 
    /* Clean up */
    ReleaseSysCache(tup);
    table_close(conDesc, RowExclusiveLock);
}
 
/*
 * RenameConstraintById
 *      Rename a constraint.
 *
 * Note: this isn't intended to be a user-exposed function; it doesn't check
 * permissions etc.  Currently this is only invoked when renaming an index
 * that is associated with a constraint, but it's made a little more general
 * than that with the expectation of someday having ALTER TABLE RENAME
 * CONSTRAINT.
 */
void
RenameConstraintById(Oid conId, const char *newname)
{
    Relation    conDesc;
    HeapTuple   tuple;
    Form_pg_constraint con;
 
    conDesc = table_open(ConstraintRelationId, RowExclusiveLock);
 
    tuple = SearchSysCacheCopy1(CONSTROID, ObjectIdGetDatum(conId));
    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "cache lookup failed for constraint %u", conId);
    con = (Form_pg_constraint) GETSTRUCT(tuple);
 
    /*
     * For user-friendliness, check whether the name is already in use.
     */
    if (OidIsValid(con->conrelid) &&
        ConstraintNameIsUsed(CONSTRAINT_RELATION,
                             con->conrelid,
                             newname))
        ereport(ERROR,
                (errcode(ERRCODE_DUPLICATE_OBJECT),
                 errmsg("constraint \"%s\" for relation \"%s\" already exists",
                        newname, get_rel_name(con->conrelid))));
    if (OidIsValid(con->contypid) &&
        ConstraintNameIsUsed(CONSTRAINT_DOMAIN,
                             con->contypid,
                             newname))
        ereport(ERROR,
                (errcode(ERRCODE_DUPLICATE_OBJECT),
                 errmsg("constraint \"%s\" for domain %s already exists",
                        newname, format_type_be(con->contypid))));
 
    /* OK, do the rename --- tuple is a copy, so OK to scribble on it */
    namestrcpy(&(con->conname), newname);
 
    CatalogTupleUpdate(conDesc, &tuple->t_self, tuple);
 
    InvokeObjectPostAlterHook(ConstraintRelationId, conId, 0);
 
    heap_freetuple(tuple);
    table_close(conDesc, RowExclusiveLock);
}
 
/*
 * AlterConstraintNamespaces
 *      Find any constraints belonging to the specified object,
 *      and move them to the specified new namespace.
 *
 * isType indicates whether the owning object is a type or a relation.
 */
void
AlterConstraintNamespaces(Oid ownerId, Oid oldNspId,
                          Oid newNspId, bool isType, ObjectAddresses *objsMoved)
{
    Relation    conRel;
    ScanKeyData key[2];
    SysScanDesc scan;
    HeapTuple   tup;
 
    conRel = table_open(ConstraintRelationId, RowExclusiveLock);
 
    ScanKeyInit(&key[0],
                Anum_pg_constraint_conrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(isType ? InvalidOid : ownerId));
    ScanKeyInit(&key[1],
                Anum_pg_constraint_contypid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(isType ? ownerId : InvalidOid));
 
    scan = systable_beginscan(conRel, ConstraintRelidTypidNameIndexId, true,
                              NULL, 2, key);
 
    while (HeapTupleIsValid((tup = systable_getnext(scan))))
    {
        Form_pg_constraint conform = (Form_pg_constraint) GETSTRUCT(tup);
        ObjectAddress thisobj;
 
        ObjectAddressSet(thisobj, ConstraintRelationId, conform->oid);
 
        if (object_address_present(&thisobj, objsMoved))
            continue;
 
        /* Don't update if the object is already part of the namespace */
        if (conform->connamespace == oldNspId && oldNspId != newNspId)
        {
            tup = heap_copytuple(tup);
            conform = (Form_pg_constraint) GETSTRUCT(tup);
 
            conform->connamespace = newNspId;
 
            CatalogTupleUpdate(conRel, &tup->t_self, tup);
 
            /*
             * Note: currently, the constraint will not have its own
             * dependency on the namespace, so we don't need to do
             * changeDependencyFor().
             */
        }
 
        InvokeObjectPostAlterHook(ConstraintRelationId, thisobj.objectId, 0);
 
        add_exact_object_address(&thisobj, objsMoved);
    }
 
    systable_endscan(scan);
 
    table_close(conRel, RowExclusiveLock);
}
 
/*
 * ConstraintSetParentConstraint
 *      Set a partition's constraint as child of its parent constraint,
 *      or remove the linkage if parentConstrId is InvalidOid.
 *
 * This updates the constraint's pg_constraint row to show it as inherited, and
 * adds PARTITION dependencies to prevent the constraint from being deleted
 * on its own.  Alternatively, reverse that.
 */
void
ConstraintSetParentConstraint(Oid childConstrId,
                              Oid parentConstrId,
                              Oid childTableId)
{
    Relation    constrRel;
    Form_pg_constraint constrForm;
    HeapTuple   tuple,
                newtup;
    ObjectAddress depender;
    ObjectAddress referenced;
 
    constrRel = table_open(ConstraintRelationId, RowExclusiveLock);
    tuple = SearchSysCache1(CONSTROID, ObjectIdGetDatum(childConstrId));
    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "cache lookup failed for constraint %u", childConstrId);
    newtup = heap_copytuple(tuple);
    constrForm = (Form_pg_constraint) GETSTRUCT(newtup);
    if (OidIsValid(parentConstrId))
    {
        /* don't allow setting parent for a constraint that already has one */
        Assert(constrForm->coninhcount == 0);
        if (constrForm->conparentid != InvalidOid)
            elog(ERROR, "constraint %u already has a parent constraint",
                 childConstrId);
 
        constrForm->conislocal = false;
        constrForm->coninhcount++;
        if (constrForm->coninhcount < 0)
            ereport(ERROR,
                    errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                    errmsg("too many inheritance parents"));
        constrForm->conparentid = parentConstrId;
 
        CatalogTupleUpdate(constrRel, &tuple->t_self, newtup);
 
        ObjectAddressSet(depender, ConstraintRelationId, childConstrId);
 
        ObjectAddressSet(referenced, ConstraintRelationId, parentConstrId);
        recordDependencyOn(&depender, &referenced, DEPENDENCY_PARTITION_PRI);
 
        ObjectAddressSet(referenced, RelationRelationId, childTableId);
        recordDependencyOn(&depender, &referenced, DEPENDENCY_PARTITION_SEC);
    }
    else
    {
        constrForm->coninhcount--;
        constrForm->conislocal = true;
        constrForm->conparentid = InvalidOid;
 
        /* Make sure there's no further inheritance. */
        Assert(constrForm->coninhcount == 0);
 
        CatalogTupleUpdate(constrRel, &tuple->t_self, newtup);
 
        deleteDependencyRecordsForClass(ConstraintRelationId, childConstrId,
                                        ConstraintRelationId,
                                        DEPENDENCY_PARTITION_PRI);
        deleteDependencyRecordsForClass(ConstraintRelationId, childConstrId,
                                        RelationRelationId,
                                        DEPENDENCY_PARTITION_SEC);
    }
 
    ReleaseSysCache(tuple);
    table_close(constrRel, RowExclusiveLock);
}
 
 
/*
 * get_relation_constraint_oid
 *      Find a constraint on the specified relation with the specified name.
 *      Returns constraint's OID.
 */
Oid
get_relation_constraint_oid(Oid relid, const char *conname, bool missing_ok)
{
    Relation    pg_constraint;
    HeapTuple   tuple;
    SysScanDesc scan;
    ScanKeyData skey[3];
    Oid         conOid = InvalidOid;
 
    pg_constraint = table_open(ConstraintRelationId, AccessShareLock);
 
    ScanKeyInit(&skey[0],
                Anum_pg_constraint_conrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(relid));
    ScanKeyInit(&skey[1],
                Anum_pg_constraint_contypid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(InvalidOid));
    ScanKeyInit(&skey[2],
                Anum_pg_constraint_conname,
                BTEqualStrategyNumber, F_NAMEEQ,
                CStringGetDatum(conname));
 
    scan = systable_beginscan(pg_constraint, ConstraintRelidTypidNameIndexId, true,
                              NULL, 3, skey);
 
    /* There can be at most one matching row */
    if (HeapTupleIsValid(tuple = systable_getnext(scan)))
        conOid = ((Form_pg_constraint) GETSTRUCT(tuple))->oid;
 
    systable_endscan(scan);
 
    /* If no such constraint exists, complain */
    if (!OidIsValid(conOid) && !missing_ok)
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("constraint \"%s\" for table \"%s\" does not exist",
                        conname, get_rel_name(relid))));
 
    table_close(pg_constraint, AccessShareLock);
 
    return conOid;
}
 
/*
 * get_relation_constraint_attnos
 *      Find a constraint on the specified relation with the specified name
 *      and return the constrained columns.
 *
 * Returns a Bitmapset of the column attnos of the constrained columns, with
 * attnos being offset by FirstLowInvalidHeapAttributeNumber so that system
 * columns can be represented.
 *
 * *constraintOid is set to the OID of the constraint, or InvalidOid on
 * failure.
 */
Bitmapset *
get_relation_constraint_attnos(Oid relid, const char *conname,
                               bool missing_ok, Oid *constraintOid)
{
    Bitmapset  *conattnos = NULL;
    Relation    pg_constraint;
    HeapTuple   tuple;
    SysScanDesc scan;
    ScanKeyData skey[3];
 
    /* Set *constraintOid, to avoid complaints about uninitialized vars */
    *constraintOid = InvalidOid;
 
    pg_constraint = table_open(ConstraintRelationId, AccessShareLock);
 
    ScanKeyInit(&skey[0],
                Anum_pg_constraint_conrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(relid));
    ScanKeyInit(&skey[1],
                Anum_pg_constraint_contypid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(InvalidOid));
    ScanKeyInit(&skey[2],
                Anum_pg_constraint_conname,
                BTEqualStrategyNumber, F_NAMEEQ,
                CStringGetDatum(conname));
 
    scan = systable_beginscan(pg_constraint, ConstraintRelidTypidNameIndexId, true,
                              NULL, 3, skey);
 
    /* There can be at most one matching row */
    if (HeapTupleIsValid(tuple = systable_getnext(scan)))
    {
        Datum       adatum;
        bool        isNull;
 
        *constraintOid = ((Form_pg_constraint) GETSTRUCT(tuple))->oid;
 
        /* Extract the conkey array, ie, attnums of constrained columns */
        adatum = heap_getattr(tuple, Anum_pg_constraint_conkey,
                              RelationGetDescr(pg_constraint), &isNull);
        if (!isNull)
        {
            ArrayType  *arr;
            int         numcols;
            int16      *attnums;
            int         i;
 
            arr = DatumGetArrayTypeP(adatum);   /* ensure not toasted */
            numcols = ARR_DIMS(arr)[0];
            if (ARR_NDIM(arr) != 1 ||
                numcols < 0 ||
                ARR_HASNULL(arr) ||
                ARR_ELEMTYPE(arr) != INT2OID)
                elog(ERROR, "conkey is not a 1-D smallint array");
            attnums = (int16 *) ARR_DATA_PTR(arr);
 
            /* Construct the result value */
            for (i = 0; i < numcols; i++)
            {
                conattnos = bms_add_member(conattnos,
                                           attnums[i] - FirstLowInvalidHeapAttributeNumber);
            }
        }
    }
 
    systable_endscan(scan);
 
    /* If no such constraint exists, complain */
    if (!OidIsValid(*constraintOid) && !missing_ok)
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("constraint \"%s\" for table \"%s\" does not exist",
                        conname, get_rel_name(relid))));
 
    table_close(pg_constraint, AccessShareLock);
 
    return conattnos;
}
 
/*
 * Return the OID of the constraint enforced by the given index in the
 * given relation; or InvalidOid if no such index is catalogued.
 *
 * Much like get_constraint_index, this function is concerned only with the
 * one constraint that "owns" the given index.  Therefore, constraints of
 * types other than unique, primary-key, and exclusion are ignored.
 */
Oid
get_relation_idx_constraint_oid(Oid relationId, Oid indexId)
{
    Relation    pg_constraint;
    SysScanDesc scan;
    ScanKeyData key;
    HeapTuple   tuple;
    Oid         constraintId = InvalidOid;
 
    pg_constraint = table_open(ConstraintRelationId, AccessShareLock);
 
    ScanKeyInit(&key,
                Anum_pg_constraint_conrelid,
                BTEqualStrategyNumber,
                F_OIDEQ,
                ObjectIdGetDatum(relationId));
    scan = systable_beginscan(pg_constraint, ConstraintRelidTypidNameIndexId,
                              true, NULL, 1, &key);
    while ((tuple = systable_getnext(scan)) != NULL)
    {
        Form_pg_constraint constrForm;
 
        constrForm = (Form_pg_constraint) GETSTRUCT(tuple);
 
        /* See above */
        if (constrForm->contype != CONSTRAINT_PRIMARY &&
            constrForm->contype != CONSTRAINT_UNIQUE &&
            constrForm->contype != CONSTRAINT_EXCLUSION)
            continue;
 
        if (constrForm->conindid == indexId)
        {
            constraintId = constrForm->oid;
            break;
        }
    }
    systable_endscan(scan);
 
    table_close(pg_constraint, AccessShareLock);
    return constraintId;
}
 
/*
 * get_domain_constraint_oid
 *      Find a constraint on the specified domain with the specified name.
 *      Returns constraint's OID.
 */
Oid
get_domain_constraint_oid(Oid typid, const char *conname, bool missing_ok)
{
    Relation    pg_constraint;
    HeapTuple   tuple;
    SysScanDesc scan;
    ScanKeyData skey[3];
    Oid         conOid = InvalidOid;
 
    pg_constraint = table_open(ConstraintRelationId, AccessShareLock);
 
    ScanKeyInit(&skey[0],
                Anum_pg_constraint_conrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(InvalidOid));
    ScanKeyInit(&skey[1],
                Anum_pg_constraint_contypid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(typid));
    ScanKeyInit(&skey[2],
                Anum_pg_constraint_conname,
                BTEqualStrategyNumber, F_NAMEEQ,
                CStringGetDatum(conname));
 
    scan = systable_beginscan(pg_constraint, ConstraintRelidTypidNameIndexId, true,
                              NULL, 3, skey);
 
    /* There can be at most one matching row */
    if (HeapTupleIsValid(tuple = systable_getnext(scan)))
        conOid = ((Form_pg_constraint) GETSTRUCT(tuple))->oid;
 
    systable_endscan(scan);
 
    /* If no such constraint exists, complain */
    if (!OidIsValid(conOid) && !missing_ok)
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("constraint \"%s\" for domain %s does not exist",
                        conname, format_type_be(typid))));
 
    table_close(pg_constraint, AccessShareLock);
 
    return conOid;
}
 
/*
 * get_primary_key_attnos
 *      Identify the columns in a relation's primary key, if any.
 *
 * Returns a Bitmapset of the column attnos of the primary key's columns,
 * with attnos being offset by FirstLowInvalidHeapAttributeNumber so that
 * system columns can be represented.
 *
 * If there is no primary key, return NULL.  We also return NULL if the pkey
 * constraint is deferrable and deferrableOk is false.
 *
 * *constraintOid is set to the OID of the pkey constraint, or InvalidOid
 * on failure.
 */
Bitmapset *
get_primary_key_attnos(Oid relid, bool deferrableOk, Oid *constraintOid)
{
    Bitmapset  *pkattnos = NULL;
    Relation    pg_constraint;
    HeapTuple   tuple;
    SysScanDesc scan;
    ScanKeyData skey[1];
 
    /* Set *constraintOid, to avoid complaints about uninitialized vars */
    *constraintOid = InvalidOid;
 
    /* Scan pg_constraint for constraints of the target rel */
    pg_constraint = table_open(ConstraintRelationId, AccessShareLock);
 
    ScanKeyInit(&skey[0],
                Anum_pg_constraint_conrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(relid));
 
    scan = systable_beginscan(pg_constraint, ConstraintRelidTypidNameIndexId, true,
                              NULL, 1, skey);
 
    while (HeapTupleIsValid(tuple = systable_getnext(scan)))
    {
        Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(tuple);
        Datum       adatum;
        bool        isNull;
        ArrayType  *arr;
        int16      *attnums;
        int         numkeys;
        int         i;
 
        /* Skip constraints that are not PRIMARY KEYs */
        if (con->contype != CONSTRAINT_PRIMARY)
            continue;
 
        /*
         * If the primary key is deferrable, but we've been instructed to
         * ignore deferrable constraints, then we might as well give up
         * searching, since there can only be a single primary key on a table.
         */
        if (con->condeferrable && !deferrableOk)
            break;
 
        /* Extract the conkey array, ie, attnums of PK's columns */
        adatum = heap_getattr(tuple, Anum_pg_constraint_conkey,
                              RelationGetDescr(pg_constraint), &isNull);
        if (isNull)
            elog(ERROR, "null conkey for constraint %u",
                 ((Form_pg_constraint) GETSTRUCT(tuple))->oid);
        arr = DatumGetArrayTypeP(adatum);   /* ensure not toasted */
        numkeys = ARR_DIMS(arr)[0];
        if (ARR_NDIM(arr) != 1 ||
            numkeys < 0 ||
            ARR_HASNULL(arr) ||
            ARR_ELEMTYPE(arr) != INT2OID)
            elog(ERROR, "conkey is not a 1-D smallint array");
        attnums = (int16 *) ARR_DATA_PTR(arr);
 
        /* Construct the result value */
        for (i = 0; i < numkeys; i++)
        {
            pkattnos = bms_add_member(pkattnos,
                                      attnums[i] - FirstLowInvalidHeapAttributeNumber);
        }
        *constraintOid = ((Form_pg_constraint) GETSTRUCT(tuple))->oid;
 
        /* No need to search further */
        break;
    }
 
    systable_endscan(scan);
 
    table_close(pg_constraint, AccessShareLock);
 
    return pkattnos;
}
 
/*
 * Extract data from the pg_constraint tuple of a foreign-key constraint.
 *
 * All arguments save the first are output arguments.  All output arguments
 * other than numfks, conkey and confkey can be passed as NULL if caller
 * doesn't need them.
 */
void
DeconstructFkConstraintRow(HeapTuple tuple, int *numfks,
                           AttrNumber *conkey, AttrNumber *confkey,
                           Oid *pf_eq_oprs, Oid *pp_eq_oprs, Oid *ff_eq_oprs,
                           int *num_fk_del_set_cols, AttrNumber *fk_del_set_cols)
{
    Datum       adatum;
    bool        isNull;
    ArrayType  *arr;
    int         numkeys;
 
    /*
     * We expect the arrays to be 1-D arrays of the right types; verify that.
     * We don't need to use deconstruct_array() since the array data is just
     * going to look like a C array of values.
     */
    adatum = SysCacheGetAttrNotNull(CONSTROID, tuple,
                                    Anum_pg_constraint_conkey);
    arr = DatumGetArrayTypeP(adatum);   /* ensure not toasted */
    if (ARR_NDIM(arr) != 1 ||
        ARR_HASNULL(arr) ||
        ARR_ELEMTYPE(arr) != INT2OID)
        elog(ERROR, "conkey is not a 1-D smallint array");
    numkeys = ARR_DIMS(arr)[0];
    if (numkeys <= 0 || numkeys > INDEX_MAX_KEYS)
        elog(ERROR, "foreign key constraint cannot have %d columns", numkeys);
    memcpy(conkey, ARR_DATA_PTR(arr), numkeys * sizeof(int16));
    if ((Pointer) arr != DatumGetPointer(adatum))
        pfree(arr);             /* free de-toasted copy, if any */
 
    adatum = SysCacheGetAttrNotNull(CONSTROID, tuple,
                                    Anum_pg_constraint_confkey);
    arr = DatumGetArrayTypeP(adatum);   /* ensure not toasted */
    if (ARR_NDIM(arr) != 1 ||
        ARR_DIMS(arr)[0] != numkeys ||
        ARR_HASNULL(arr) ||
        ARR_ELEMTYPE(arr) != INT2OID)
        elog(ERROR, "confkey is not a 1-D smallint array");
    memcpy(confkey, ARR_DATA_PTR(arr), numkeys * sizeof(int16));
    if ((Pointer) arr != DatumGetPointer(adatum))
        pfree(arr);             /* free de-toasted copy, if any */
 
    if (pf_eq_oprs)
    {
        adatum = SysCacheGetAttrNotNull(CONSTROID, tuple,
                                        Anum_pg_constraint_conpfeqop);
        arr = DatumGetArrayTypeP(adatum);   /* ensure not toasted */
        /* see TryReuseForeignKey if you change the test below */
        if (ARR_NDIM(arr) != 1 ||
            ARR_DIMS(arr)[0] != numkeys ||
            ARR_HASNULL(arr) ||
            ARR_ELEMTYPE(arr) != OIDOID)
            elog(ERROR, "conpfeqop is not a 1-D Oid array");
        memcpy(pf_eq_oprs, ARR_DATA_PTR(arr), numkeys * sizeof(Oid));
        if ((Pointer) arr != DatumGetPointer(adatum))
            pfree(arr);         /* free de-toasted copy, if any */
    }
 
    if (pp_eq_oprs)
    {
        adatum = SysCacheGetAttrNotNull(CONSTROID, tuple,
                                        Anum_pg_constraint_conppeqop);
        arr = DatumGetArrayTypeP(adatum);   /* ensure not toasted */
        if (ARR_NDIM(arr) != 1 ||
            ARR_DIMS(arr)[0] != numkeys ||
            ARR_HASNULL(arr) ||
            ARR_ELEMTYPE(arr) != OIDOID)
            elog(ERROR, "conppeqop is not a 1-D Oid array");
        memcpy(pp_eq_oprs, ARR_DATA_PTR(arr), numkeys * sizeof(Oid));
        if ((Pointer) arr != DatumGetPointer(adatum))
            pfree(arr);         /* free de-toasted copy, if any */
    }
 
    if (ff_eq_oprs)
    {
        adatum = SysCacheGetAttrNotNull(CONSTROID, tuple,
                                        Anum_pg_constraint_conffeqop);
        arr = DatumGetArrayTypeP(adatum);   /* ensure not toasted */
        if (ARR_NDIM(arr) != 1 ||
            ARR_DIMS(arr)[0] != numkeys ||
            ARR_HASNULL(arr) ||
            ARR_ELEMTYPE(arr) != OIDOID)
            elog(ERROR, "conffeqop is not a 1-D Oid array");
        memcpy(ff_eq_oprs, ARR_DATA_PTR(arr), numkeys * sizeof(Oid));
        if ((Pointer) arr != DatumGetPointer(adatum))
            pfree(arr);         /* free de-toasted copy, if any */
    }
 
    if (fk_del_set_cols)
    {
        adatum = SysCacheGetAttr(CONSTROID, tuple,
                                 Anum_pg_constraint_confdelsetcols, &isNull);
        if (isNull)
        {
            *num_fk_del_set_cols = 0;
        }
        else
        {
            int         num_delete_cols;
 
            arr = DatumGetArrayTypeP(adatum);   /* ensure not toasted */
            if (ARR_NDIM(arr) != 1 ||
                ARR_HASNULL(arr) ||
                ARR_ELEMTYPE(arr) != INT2OID)
                elog(ERROR, "confdelsetcols is not a 1-D smallint array");
            num_delete_cols = ARR_DIMS(arr)[0];
            memcpy(fk_del_set_cols, ARR_DATA_PTR(arr), num_delete_cols * sizeof(int16));
            if ((Pointer) arr != DatumGetPointer(adatum))
                pfree(arr);     /* free de-toasted copy, if any */
 
            *num_fk_del_set_cols = num_delete_cols;
        }
    }
 
    *numfks = numkeys;
}
 
/*
 * Determine whether a relation can be proven functionally dependent on
 * a set of grouping columns.  If so, return true and add the pg_constraint
 * OIDs of the constraints needed for the proof to the *constraintDeps list.
 *
 * grouping_columns is a list of grouping expressions, in which columns of
 * the rel of interest are Vars with the indicated varno/varlevelsup.
 *
 * Currently we only check to see if the rel has a primary key that is a
 * subset of the grouping_columns.  We could also use plain unique constraints
 * if all their columns are known not null, but there's a problem: we need
 * to be able to represent the not-null-ness as part of the constraints added
 * to *constraintDeps.  FIXME whenever not-null constraints get represented
 * in pg_constraint.
 */
bool
check_functional_grouping(Oid relid,
                          Index varno, Index varlevelsup,
                          List *grouping_columns,
                          List **constraintDeps)
{
    Bitmapset  *pkattnos;
    Bitmapset  *groupbyattnos;
    Oid         constraintOid;
    ListCell   *gl;
 
    /* If the rel has no PK, then we can't prove functional dependency */
    pkattnos = get_primary_key_attnos(relid, false, &constraintOid);
    if (pkattnos == NULL)
        return false;
 
    /* Identify all the rel's columns that appear in grouping_columns */
    groupbyattnos = NULL;
    foreach(gl, grouping_columns)
    {
        Var        *gvar = (Var *) lfirst(gl);
 
        if (IsA(gvar, Var) &&
            gvar->varno == varno &&
            gvar->varlevelsup == varlevelsup)
            groupbyattnos = bms_add_member(groupbyattnos,
                                           gvar->varattno - FirstLowInvalidHeapAttributeNumber);
    }
 
    if (bms_is_subset(pkattnos, groupbyattnos))
    {
        /* The PK is a subset of grouping_columns, so we win */
        *constraintDeps = lappend_oid(*constraintDeps, constraintOid);
        return true;
    }
 
    return false;
}