Update copyright for 2022

[pgsql.git] / src / backend / foreign / foreign.c

/*-------------------------------------------------------------------------
 *
 * foreign.c
 *                support for foreign-data wrappers, servers and user mappings.
 *
 * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *                src/backend/foreign/foreign.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/htup_details.h"
#include "access/reloptions.h"
#include "catalog/pg_foreign_data_wrapper.h"
#include "catalog/pg_foreign_server.h"
#include "catalog/pg_foreign_table.h"
#include "catalog/pg_user_mapping.h"
#include "foreign/fdwapi.h"
#include "foreign/foreign.h"
#include "lib/stringinfo.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/syscache.h"


/*
 * GetForeignDataWrapper -      look up the foreign-data wrapper by OID.
 */
ForeignDataWrapper *
GetForeignDataWrapper(Oid fdwid)
{
        return GetForeignDataWrapperExtended(fdwid, 0);
}


/*
 * GetForeignDataWrapperExtended -      look up the foreign-data wrapper
 * by OID. If flags uses FDW_MISSING_OK, return NULL if the object cannot
 * be found instead of raising an error.
 */
ForeignDataWrapper *
GetForeignDataWrapperExtended(Oid fdwid, bits16 flags)
{
        Form_pg_foreign_data_wrapper fdwform;
        ForeignDataWrapper *fdw;
        Datum           datum;
        HeapTuple       tp;
        bool            isnull;

        tp = SearchSysCache1(FOREIGNDATAWRAPPEROID, ObjectIdGetDatum(fdwid));

        if (!HeapTupleIsValid(tp))
        {
                if ((flags & FDW_MISSING_OK) == 0)
                        elog(ERROR, "cache lookup failed for foreign-data wrapper %u", fdwid);
                return NULL;
        }

        fdwform = (Form_pg_foreign_data_wrapper) GETSTRUCT(tp);

        fdw = (ForeignDataWrapper *) palloc(sizeof(ForeignDataWrapper));
        fdw->fdwid = fdwid;
        fdw->owner = fdwform->fdwowner;
        fdw->fdwname = pstrdup(NameStr(fdwform->fdwname));
        fdw->fdwhandler = fdwform->fdwhandler;
        fdw->fdwvalidator = fdwform->fdwvalidator;

        /* Extract the fdwoptions */
        datum = SysCacheGetAttr(FOREIGNDATAWRAPPEROID,
                                                        tp,
                                                        Anum_pg_foreign_data_wrapper_fdwoptions,
                                                        &isnull);
        if (isnull)
                fdw->options = NIL;
        else
                fdw->options = untransformRelOptions(datum);

        ReleaseSysCache(tp);

        return fdw;
}


/*
 * GetForeignDataWrapperByName - look up the foreign-data wrapper
 * definition by name.
 */
ForeignDataWrapper *
GetForeignDataWrapperByName(const char *fdwname, bool missing_ok)
{
        Oid                     fdwId = get_foreign_data_wrapper_oid(fdwname, missing_ok);

        if (!OidIsValid(fdwId))
                return NULL;

        return GetForeignDataWrapper(fdwId);
}


/*
 * GetForeignServer - look up the foreign server definition.
 */
ForeignServer *
GetForeignServer(Oid serverid)
{
        return GetForeignServerExtended(serverid, 0);
}


/*
 * GetForeignServerExtended - look up the foreign server definition. If
 * flags uses FSV_MISSING_OK, return NULL if the object cannot be found
 * instead of raising an error.
 */
ForeignServer *
GetForeignServerExtended(Oid serverid, bits16 flags)
{
        Form_pg_foreign_server serverform;
        ForeignServer *server;
        HeapTuple       tp;
        Datum           datum;
        bool            isnull;

        tp = SearchSysCache1(FOREIGNSERVEROID, ObjectIdGetDatum(serverid));

        if (!HeapTupleIsValid(tp))
        {
                if ((flags & FSV_MISSING_OK) == 0)
                        elog(ERROR, "cache lookup failed for foreign server %u", serverid);
                return NULL;
        }

        serverform = (Form_pg_foreign_server) GETSTRUCT(tp);

        server = (ForeignServer *) palloc(sizeof(ForeignServer));
        server->serverid = serverid;
        server->servername = pstrdup(NameStr(serverform->srvname));
        server->owner = serverform->srvowner;
        server->fdwid = serverform->srvfdw;

        /* Extract server type */
        datum = SysCacheGetAttr(FOREIGNSERVEROID,
                                                        tp,
                                                        Anum_pg_foreign_server_srvtype,
                                                        &isnull);
        server->servertype = isnull ? NULL : TextDatumGetCString(datum);

        /* Extract server version */
        datum = SysCacheGetAttr(FOREIGNSERVEROID,
                                                        tp,
                                                        Anum_pg_foreign_server_srvversion,
                                                        &isnull);
        server->serverversion = isnull ? NULL : TextDatumGetCString(datum);

        /* Extract the srvoptions */
        datum = SysCacheGetAttr(FOREIGNSERVEROID,
                                                        tp,
                                                        Anum_pg_foreign_server_srvoptions,
                                                        &isnull);
        if (isnull)
                server->options = NIL;
        else
                server->options = untransformRelOptions(datum);

        ReleaseSysCache(tp);

        return server;
}


/*
 * GetForeignServerByName - look up the foreign server definition by name.
 */
ForeignServer *
GetForeignServerByName(const char *srvname, bool missing_ok)
{
        Oid                     serverid = get_foreign_server_oid(srvname, missing_ok);

        if (!OidIsValid(serverid))
                return NULL;

        return GetForeignServer(serverid);
}


/*
 * GetUserMapping - look up the user mapping.
 *
 * If no mapping is found for the supplied user, we also look for
 * PUBLIC mappings (userid == InvalidOid).
 */
UserMapping *
GetUserMapping(Oid userid, Oid serverid)
{
        Datum           datum;
        HeapTuple       tp;
        bool            isnull;
        UserMapping *um;

        tp = SearchSysCache2(USERMAPPINGUSERSERVER,
                                                 ObjectIdGetDatum(userid),
                                                 ObjectIdGetDatum(serverid));

        if (!HeapTupleIsValid(tp))
        {
                /* Not found for the specific user -- try PUBLIC */
                tp = SearchSysCache2(USERMAPPINGUSERSERVER,
                                                         ObjectIdGetDatum(InvalidOid),
                                                         ObjectIdGetDatum(serverid));
        }

        if (!HeapTupleIsValid(tp))
                ereport(ERROR,
                                (errcode(ERRCODE_UNDEFINED_OBJECT),
                                 errmsg("user mapping not found for \"%s\"",
                                                MappingUserName(userid))));

        um = (UserMapping *) palloc(sizeof(UserMapping));
        um->umid = ((Form_pg_user_mapping) GETSTRUCT(tp))->oid;
        um->userid = userid;
        um->serverid = serverid;

        /* Extract the umoptions */
        datum = SysCacheGetAttr(USERMAPPINGUSERSERVER,
                                                        tp,
                                                        Anum_pg_user_mapping_umoptions,
                                                        &isnull);
        if (isnull)
                um->options = NIL;
        else
                um->options = untransformRelOptions(datum);

        ReleaseSysCache(tp);

        return um;
}


/*
 * GetForeignTable - look up the foreign table definition by relation oid.
 */
ForeignTable *
GetForeignTable(Oid relid)
{
        Form_pg_foreign_table tableform;
        ForeignTable *ft;
        HeapTuple       tp;
        Datum           datum;
        bool            isnull;

        tp = SearchSysCache1(FOREIGNTABLEREL, ObjectIdGetDatum(relid));
        if (!HeapTupleIsValid(tp))
                elog(ERROR, "cache lookup failed for foreign table %u", relid);
        tableform = (Form_pg_foreign_table) GETSTRUCT(tp);

        ft = (ForeignTable *) palloc(sizeof(ForeignTable));
        ft->relid = relid;
        ft->serverid = tableform->ftserver;

        /* Extract the ftoptions */
        datum = SysCacheGetAttr(FOREIGNTABLEREL,
                                                        tp,
                                                        Anum_pg_foreign_table_ftoptions,
                                                        &isnull);
        if (isnull)
                ft->options = NIL;
        else
                ft->options = untransformRelOptions(datum);

        ReleaseSysCache(tp);

        return ft;
}


/*
 * GetForeignColumnOptions - Get attfdwoptions of given relation/attnum
 * as list of DefElem.
 */
List *
GetForeignColumnOptions(Oid relid, AttrNumber attnum)
{
        List       *options;
        HeapTuple       tp;
        Datum           datum;
        bool            isnull;

        tp = SearchSysCache2(ATTNUM,
                                                 ObjectIdGetDatum(relid),
                                                 Int16GetDatum(attnum));
        if (!HeapTupleIsValid(tp))
                elog(ERROR, "cache lookup failed for attribute %d of relation %u",
                         attnum, relid);
        datum = SysCacheGetAttr(ATTNUM,
                                                        tp,
                                                        Anum_pg_attribute_attfdwoptions,
                                                        &isnull);
        if (isnull)
                options = NIL;
        else
                options = untransformRelOptions(datum);

        ReleaseSysCache(tp);

        return options;
}


/*
 * GetFdwRoutine - call the specified foreign-data wrapper handler routine
 * to get its FdwRoutine struct.
 */
FdwRoutine *
GetFdwRoutine(Oid fdwhandler)
{
        Datum           datum;
        FdwRoutine *routine;

        datum = OidFunctionCall0(fdwhandler);
        routine = (FdwRoutine *) DatumGetPointer(datum);

        if (routine == NULL || !IsA(routine, FdwRoutine))
                elog(ERROR, "foreign-data wrapper handler function %u did not return an FdwRoutine struct",
                         fdwhandler);

        return routine;
}


/*
 * GetForeignServerIdByRelId - look up the foreign server
 * for the given foreign table, and return its OID.
 */
Oid
GetForeignServerIdByRelId(Oid relid)
{
        HeapTuple       tp;
        Form_pg_foreign_table tableform;
        Oid                     serverid;

        tp = SearchSysCache1(FOREIGNTABLEREL, ObjectIdGetDatum(relid));
        if (!HeapTupleIsValid(tp))
                elog(ERROR, "cache lookup failed for foreign table %u", relid);
        tableform = (Form_pg_foreign_table) GETSTRUCT(tp);
        serverid = tableform->ftserver;
        ReleaseSysCache(tp);

        return serverid;
}


/*
 * GetFdwRoutineByServerId - look up the handler of the foreign-data wrapper
 * for the given foreign server, and retrieve its FdwRoutine struct.
 */
FdwRoutine *
GetFdwRoutineByServerId(Oid serverid)
{
        HeapTuple       tp;
        Form_pg_foreign_data_wrapper fdwform;
        Form_pg_foreign_server serverform;
        Oid                     fdwid;
        Oid                     fdwhandler;

        /* Get foreign-data wrapper OID for the server. */
        tp = SearchSysCache1(FOREIGNSERVEROID, ObjectIdGetDatum(serverid));
        if (!HeapTupleIsValid(tp))
                elog(ERROR, "cache lookup failed for foreign server %u", serverid);
        serverform = (Form_pg_foreign_server) GETSTRUCT(tp);
        fdwid = serverform->srvfdw;
        ReleaseSysCache(tp);

        /* Get handler function OID for the FDW. */
        tp = SearchSysCache1(FOREIGNDATAWRAPPEROID, ObjectIdGetDatum(fdwid));
        if (!HeapTupleIsValid(tp))
                elog(ERROR, "cache lookup failed for foreign-data wrapper %u", fdwid);
        fdwform = (Form_pg_foreign_data_wrapper) GETSTRUCT(tp);
        fdwhandler = fdwform->fdwhandler;

        /* Complain if FDW has been set to NO HANDLER. */
        if (!OidIsValid(fdwhandler))
                ereport(ERROR,
                                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                                 errmsg("foreign-data wrapper \"%s\" has no handler",
                                                NameStr(fdwform->fdwname))));

        ReleaseSysCache(tp);

        /* And finally, call the handler function. */
        return GetFdwRoutine(fdwhandler);
}


/*
 * GetFdwRoutineByRelId - look up the handler of the foreign-data wrapper
 * for the given foreign table, and retrieve its FdwRoutine struct.
 */
FdwRoutine *
GetFdwRoutineByRelId(Oid relid)
{
        Oid                     serverid;

        /* Get server OID for the foreign table. */
        serverid = GetForeignServerIdByRelId(relid);

        /* Now retrieve server's FdwRoutine struct. */
        return GetFdwRoutineByServerId(serverid);
}

/*
 * GetFdwRoutineForRelation - look up the handler of the foreign-data wrapper
 * for the given foreign table, and retrieve its FdwRoutine struct.
 *
 * This function is preferred over GetFdwRoutineByRelId because it caches
 * the data in the relcache entry, saving a number of catalog lookups.
 *
 * If makecopy is true then the returned data is freshly palloc'd in the
 * caller's memory context.  Otherwise, it's a pointer to the relcache data,
 * which will be lost in any relcache reset --- so don't rely on it long.
 */
FdwRoutine *
GetFdwRoutineForRelation(Relation relation, bool makecopy)
{
        FdwRoutine *fdwroutine;
        FdwRoutine *cfdwroutine;

        if (relation->rd_fdwroutine == NULL)
        {
                /* Get the info by consulting the catalogs and the FDW code */
                fdwroutine = GetFdwRoutineByRelId(RelationGetRelid(relation));

                /* Save the data for later reuse in CacheMemoryContext */
                cfdwroutine = (FdwRoutine *) MemoryContextAlloc(CacheMemoryContext,
                                                                                                                sizeof(FdwRoutine));
                memcpy(cfdwroutine, fdwroutine, sizeof(FdwRoutine));
                relation->rd_fdwroutine = cfdwroutine;

                /* Give back the locally palloc'd copy regardless of makecopy */
                return fdwroutine;
        }

        /* We have valid cached data --- does the caller want a copy? */
        if (makecopy)
        {
                fdwroutine = (FdwRoutine *) palloc(sizeof(FdwRoutine));
                memcpy(fdwroutine, relation->rd_fdwroutine, sizeof(FdwRoutine));
                return fdwroutine;
        }

        /* Only a short-lived reference is needed, so just hand back cached copy */
        return relation->rd_fdwroutine;
}


/*
 * IsImportableForeignTable - filter table names for IMPORT FOREIGN SCHEMA
 *
 * Returns true if given table name should be imported according to the
 * statement's import filter options.
 */
bool
IsImportableForeignTable(const char *tablename,
                                                 ImportForeignSchemaStmt *stmt)
{
        ListCell   *lc;

        switch (stmt->list_type)
        {
                case FDW_IMPORT_SCHEMA_ALL:
                        return true;

                case FDW_IMPORT_SCHEMA_LIMIT_TO:
                        foreach(lc, stmt->table_list)
                        {
                                RangeVar   *rv = (RangeVar *) lfirst(lc);

                                if (strcmp(tablename, rv->relname) == 0)
                                        return true;
                        }
                        return false;

                case FDW_IMPORT_SCHEMA_EXCEPT:
                        foreach(lc, stmt->table_list)
                        {
                                RangeVar   *rv = (RangeVar *) lfirst(lc);

                                if (strcmp(tablename, rv->relname) == 0)
                                        return false;
                        }
                        return true;
        }
        return false;                           /* shouldn't get here */
}


/*
 * deflist_to_tuplestore - Helper function to convert DefElem list to
 * tuplestore usable in SRF.
 */
static void
deflist_to_tuplestore(ReturnSetInfo *rsinfo, List *options)
{
        ListCell   *cell;
        TupleDesc       tupdesc;
        Tuplestorestate *tupstore;
        Datum           values[2];
        bool            nulls[2];
        MemoryContext per_query_ctx;
        MemoryContext oldcontext;

        /* check to see if caller supports us returning a tuplestore */
        if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
                ereport(ERROR,
                                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                 errmsg("set-valued function called in context that cannot accept a set")));
        if (!(rsinfo->allowedModes & SFRM_Materialize) ||
                rsinfo->expectedDesc == NULL)
                ereport(ERROR,
                                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                 errmsg("materialize mode required, but it is not allowed in this context")));

        per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
        oldcontext = MemoryContextSwitchTo(per_query_ctx);

        /*
         * Now prepare the result set.
         */
        tupdesc = CreateTupleDescCopy(rsinfo->expectedDesc);
        tupstore = tuplestore_begin_heap(true, false, work_mem);
        rsinfo->returnMode = SFRM_Materialize;
        rsinfo->setResult = tupstore;
        rsinfo->setDesc = tupdesc;

        foreach(cell, options)
        {
                DefElem    *def = lfirst(cell);

                values[0] = CStringGetTextDatum(def->defname);
                nulls[0] = false;
                if (def->arg)
                {
                        values[1] = CStringGetTextDatum(strVal(def->arg));
                        nulls[1] = false;
                }
                else
                {
                        values[1] = (Datum) 0;
                        nulls[1] = true;
                }
                tuplestore_putvalues(tupstore, tupdesc, values, nulls);
        }

        /* clean up and return the tuplestore */
        tuplestore_donestoring(tupstore);

        MemoryContextSwitchTo(oldcontext);
}


/*
 * Convert options array to name/value table.  Useful for information
 * schema and pg_dump.
 */
Datum
pg_options_to_table(PG_FUNCTION_ARGS)
{
        Datum           array = PG_GETARG_DATUM(0);

        deflist_to_tuplestore((ReturnSetInfo *) fcinfo->resultinfo,
                                                  untransformRelOptions(array));

        return (Datum) 0;
}


/*
 * Describes the valid options for postgresql FDW, server, and user mapping.
 */
struct ConnectionOption
{
        const char *optname;
        Oid                     optcontext;             /* Oid of catalog in which option may appear */
};

/*
 * Copied from fe-connect.c PQconninfoOptions.
 *
 * The list is small - don't bother with bsearch if it stays so.
 */
static const struct ConnectionOption libpq_conninfo_options[] = {
        {"authtype", ForeignServerRelationId},
        {"service", ForeignServerRelationId},
        {"user", UserMappingRelationId},
        {"password", UserMappingRelationId},
        {"connect_timeout", ForeignServerRelationId},
        {"dbname", ForeignServerRelationId},
        {"host", ForeignServerRelationId},
        {"hostaddr", ForeignServerRelationId},
        {"port", ForeignServerRelationId},
        {"tty", ForeignServerRelationId},
        {"options", ForeignServerRelationId},
        {"requiressl", ForeignServerRelationId},
        {"sslmode", ForeignServerRelationId},
        {"gsslib", ForeignServerRelationId},
        {NULL, InvalidOid}
};


/*
 * Check if the provided option is one of libpq conninfo options.
 * context is the Oid of the catalog the option came from, or 0 if we
 * don't care.
 */
static bool
is_conninfo_option(const char *option, Oid context)
{
        const struct ConnectionOption *opt;

        for (opt = libpq_conninfo_options; opt->optname; opt++)
                if (context == opt->optcontext && strcmp(opt->optname, option) == 0)
                        return true;
        return false;
}


/*
 * Validate the generic option given to SERVER or USER MAPPING.
 * Raise an ERROR if the option or its value is considered invalid.
 *
 * Valid server options are all libpq conninfo options except
 * user and password -- these may only appear in USER MAPPING options.
 *
 * Caution: this function is deprecated, and is now meant only for testing
 * purposes, because the list of options it knows about doesn't necessarily
 * square with those known to whichever libpq instance you might be using.
 * Inquire of libpq itself, instead.
 */
Datum
postgresql_fdw_validator(PG_FUNCTION_ARGS)
{
        List       *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
        Oid                     catalog = PG_GETARG_OID(1);

        ListCell   *cell;

        foreach(cell, options_list)
        {
                DefElem    *def = lfirst(cell);

                if (!is_conninfo_option(def->defname, catalog))
                {
                        const struct ConnectionOption *opt;
                        StringInfoData buf;

                        /*
                         * Unknown option specified, complain about it. Provide a hint
                         * with list of valid options for the object.
                         */
                        initStringInfo(&buf);
                        for (opt = libpq_conninfo_options; opt->optname; opt++)
                                if (catalog == opt->optcontext)
                                        appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
                                                                         opt->optname);

                        ereport(ERROR,
                                        (errcode(ERRCODE_SYNTAX_ERROR),
                                         errmsg("invalid option \"%s\"", def->defname),
                                         buf.len > 0
                                         ? errhint("Valid options in this context are: %s",
                                                           buf.data)
                                         : errhint("There are no valid options in this context.")));

                        PG_RETURN_BOOL(false);
                }
        }

        PG_RETURN_BOOL(true);
}


/*
 * get_foreign_data_wrapper_oid - given a FDW name, look up the OID
 *
 * If missing_ok is false, throw an error if name not found.  If true, just
 * return InvalidOid.
 */
Oid
get_foreign_data_wrapper_oid(const char *fdwname, bool missing_ok)
{
        Oid                     oid;

        oid = GetSysCacheOid1(FOREIGNDATAWRAPPERNAME,
                                                  Anum_pg_foreign_data_wrapper_oid,
                                                  CStringGetDatum(fdwname));
        if (!OidIsValid(oid) && !missing_ok)
                ereport(ERROR,
                                (errcode(ERRCODE_UNDEFINED_OBJECT),
                                 errmsg("foreign-data wrapper \"%s\" does not exist",
                                                fdwname)));
        return oid;
}


/*
 * get_foreign_server_oid - given a server name, look up the OID
 *
 * If missing_ok is false, throw an error if name not found.  If true, just
 * return InvalidOid.
 */
Oid
get_foreign_server_oid(const char *servername, bool missing_ok)
{
        Oid                     oid;

        oid = GetSysCacheOid1(FOREIGNSERVERNAME, Anum_pg_foreign_server_oid,
                                                  CStringGetDatum(servername));
        if (!OidIsValid(oid) && !missing_ok)
                ereport(ERROR,
                                (errcode(ERRCODE_UNDEFINED_OBJECT),
                                 errmsg("server \"%s\" does not exist", servername)));
        return oid;
}

/*
 * Get a copy of an existing local path for a given join relation.
 *
 * This function is usually helpful to obtain an alternate local path for EPQ
 * checks.
 *
 * Right now, this function only supports unparameterized foreign joins, so we
 * only search for unparameterized path in the given list of paths. Since we
 * are searching for a path which can be used to construct an alternative local
 * plan for a foreign join, we look for only MergeJoin, HashJoin or NestLoop
 * paths.
 *
 * If the inner or outer subpath of the chosen path is a ForeignScan, we
 * replace it with its outer subpath.  For this reason, and also because the
 * planner might free the original path later, the path returned by this
 * function is a shallow copy of the original.  There's no need to copy
 * the substructure, so we don't.
 *
 * Since the plan created using this path will presumably only be used to
 * execute EPQ checks, efficiency of the path is not a concern. But since the
 * path list in RelOptInfo is anyway sorted by total cost we are likely to
 * choose the most efficient path, which is all for the best.
 */
Path *
GetExistingLocalJoinPath(RelOptInfo *joinrel)
{
        ListCell   *lc;

        Assert(IS_JOIN_REL(joinrel));

        foreach(lc, joinrel->pathlist)
        {
                Path       *path = (Path *) lfirst(lc);
                JoinPath   *joinpath = NULL;

                /* Skip parameterized paths. */
                if (path->param_info != NULL)
                        continue;

                switch (path->pathtype)
                {
                        case T_HashJoin:
                                {
                                        HashPath   *hash_path = makeNode(HashPath);

                                        memcpy(hash_path, path, sizeof(HashPath));
                                        joinpath = (JoinPath *) hash_path;
                                }
                                break;

                        case T_NestLoop:
                                {
                                        NestPath   *nest_path = makeNode(NestPath);

                                        memcpy(nest_path, path, sizeof(NestPath));
                                        joinpath = (JoinPath *) nest_path;
                                }
                                break;

                        case T_MergeJoin:
                                {
                                        MergePath  *merge_path = makeNode(MergePath);

                                        memcpy(merge_path, path, sizeof(MergePath));
                                        joinpath = (JoinPath *) merge_path;
                                }
                                break;

                        default:

                                /*
                                 * Just skip anything else. We don't know if corresponding
                                 * plan would build the output row from whole-row references
                                 * of base relations and execute the EPQ checks.
                                 */
                                break;
                }

                /* This path isn't good for us, check next. */
                if (!joinpath)
                        continue;

                /*
                 * If either inner or outer path is a ForeignPath corresponding to a
                 * pushed down join, replace it with the fdw_outerpath, so that we
                 * maintain path for EPQ checks built entirely of local join
                 * strategies.
                 */
                if (IsA(joinpath->outerjoinpath, ForeignPath))
                {
                        ForeignPath *foreign_path;

                        foreign_path = (ForeignPath *) joinpath->outerjoinpath;
                        if (IS_JOIN_REL(foreign_path->path.parent))
                                joinpath->outerjoinpath = foreign_path->fdw_outerpath;
                }

                if (IsA(joinpath->innerjoinpath, ForeignPath))
                {
                        ForeignPath *foreign_path;

                        foreign_path = (ForeignPath *) joinpath->innerjoinpath;
                        if (IS_JOIN_REL(foreign_path->path.parent))
                                joinpath->innerjoinpath = foreign_path->fdw_outerpath;
                }

                return (Path *) joinpath;
        }
        return NULL;
}