From f4dd9741833e4499c1d7698dc869e2f8b9bfb5ce Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Tue, 18 Sep 2018 14:17:09 +0900 Subject: [PATCH 1/2] Extend lookup routines for FDW and foreign server with NULL handling The cache lookup routines for foreign-data wrappers and foreign servers are extended with an extra argument to pass flags. The only value which can be used now is to indicate if it a missing object should result in an error or not. Those new routines are added into the existing set and documented in consequence. --- doc/src/sgml/fdwhandler.sgml | 34 +++++++++++++++++++++++++++++++++ src/backend/foreign/foreign.c | 36 +++++++++++++++++++++++++++++++++-- src/include/foreign/foreign.h | 16 ++++++++++++++++ 3 files changed, 84 insertions(+), 2 deletions(-) diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml index 4ce88dd77c..6fe6122568 100644 --- a/doc/src/sgml/fdwhandler.sgml +++ b/doc/src/sgml/fdwhandler.sgml @@ -1408,6 +1408,23 @@ ReparameterizeForeignPathByChild(PlannerInfo *root, List *fdw_private, ForeignDataWrapper * +GetForeignDataWrapperExtended(Oid fdwid, uint32 flags); + + + This function returns a ForeignDataWrapper + object for the foreign-data wrapper with the given OID. A + ForeignDataWrapper object contains properties + of the FDW (see foreign/foreign.h for details). + flags is a bitwise-or'd bit mask indicating + an extra set of options. It can take the value + FDW_MISSING_OK, in which case a NULL + result is returned to the caller instead of an error for an undefined + object. + + + + +ForeignDataWrapper * GetForeignDataWrapper(Oid fdwid); @@ -1420,6 +1437,23 @@ GetForeignDataWrapper(Oid fdwid); ForeignServer * +GetForeignServerExtended(Oid serverid, uint32 flags); + + + This function returns a ForeignServer object + for the foreign server with the given OID. A + ForeignServer object contains properties + of the server (see foreign/foreign.h for details). + flags is a bitwise-or'd bit mask indicating + an extra set of options. It can take the value + FSV_MISSING_OK, in which case a NULL + result is returned to the caller instead of an error for an undefined + object. + + + + +ForeignServer * GetForeignServer(Oid serverid); diff --git a/src/backend/foreign/foreign.c b/src/backend/foreign/foreign.c index eac78a5d31..88726d9d70 100644 --- a/src/backend/foreign/foreign.c +++ b/src/backend/foreign/foreign.c @@ -33,6 +33,18 @@ */ 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, uint32 flags) { Form_pg_foreign_data_wrapper fdwform; ForeignDataWrapper *fdw; @@ -43,7 +55,11 @@ GetForeignDataWrapper(Oid fdwid) tp = SearchSysCache1(FOREIGNDATAWRAPPEROID, ObjectIdGetDatum(fdwid)); if (!HeapTupleIsValid(tp)) - elog(ERROR, "cache lookup failed for foreign-data wrapper %u", fdwid); + { + 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); @@ -91,6 +107,18 @@ GetForeignDataWrapperByName(const char *fdwname, bool missing_ok) */ 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, uint32 flags) { Form_pg_foreign_server serverform; ForeignServer *server; @@ -101,7 +129,11 @@ GetForeignServer(Oid serverid) tp = SearchSysCache1(FOREIGNSERVEROID, ObjectIdGetDatum(serverid)); if (!HeapTupleIsValid(tp)) - elog(ERROR, "cache lookup failed for foreign server %u", serverid); + { + 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); diff --git a/src/include/foreign/foreign.h b/src/include/foreign/foreign.h index 3ca12e64d2..c69af057fa 100644 --- a/src/include/foreign/foreign.h +++ b/src/include/foreign/foreign.h @@ -68,11 +68,27 @@ typedef struct ForeignTable List *options; /* ftoptions as DefElem list */ } ForeignTable; +/* Flags for GetForeignServerExtended */ +typedef enum ForeignServerExtendedOptions +{ + FSV_MISSING_OK = 1 << 0 /* no error if missing */ +} ForeignServerExtendedOptions; + +/* Flags for GetForeignDataWrapperExtended */ +typedef enum ForeignDataWrapperExtendedOptions +{ + FDW_MISSING_OK = 1 << 0 /* no error if missing */ +} ForeignDataWrapperExtendedOptions; + extern ForeignServer *GetForeignServer(Oid serverid); +extern ForeignServer *GetForeignServerExtended(Oid serverid, + uint32 flags); extern ForeignServer *GetForeignServerByName(const char *name, bool missing_ok); extern UserMapping *GetUserMapping(Oid userid, Oid serverid); extern ForeignDataWrapper *GetForeignDataWrapper(Oid fdwid); +extern ForeignDataWrapper *GetForeignDataWrapperExtended(Oid fdwid, + uint32 flags); extern ForeignDataWrapper *GetForeignDataWrapperByName(const char *name, bool missing_ok); extern ForeignTable *GetForeignTable(Oid relid); -- 2.19.0