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Commit 8fb569e

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michaelpqmichaelpq
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Introduce new extended routines for FDW and foreign server lookups
The cache lookup routines for foreign-data wrappers and foreign servers are extended with an extra argument to handle a set of flags. The only value which can be used now is to indicate if a missing object should result in an error or not, and are designed to be extensible on need. Those new routines are added into the existing set of user-visible FDW APIs and documented in consequence. They will be used for future patches to improve the SQL interface for object addresses. Author: Michael Paquier Reviewed-by: Álvaro Herrera Discussion: https://postgr.es/m/CAB7nPqSZxrSmdHK-rny7z8mi=EAFXJ5J-0RbzDw6aus=wB5azQ@mail.gmail.com
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‎doc/src/sgml/fdwhandler.sgml

Copy file name to clipboardExpand all lines: doc/src/sgml/fdwhandler.sgml
+34Lines changed: 34 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1408,6 +1408,23 @@ ReparameterizeForeignPathByChild(PlannerInfo *root, List *fdw_private,
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<para>
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<programlisting>
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ForeignDataWrapper *
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GetForeignDataWrapperExtended(Oid fdwid, bits16 flags);
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</programlisting>
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This function returns a <structname>ForeignDataWrapper</structname>
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object for the foreign-data wrapper with the given OID. A
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<structname>ForeignDataWrapper</structname> object contains properties
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of the FDW (see <filename>foreign/foreign.h</filename> for details).
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<structfield>flags</structfield> is a bitwise-or'd bit mask indicating
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an extra set of options. It can take the value
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<literal>FDW_MISSING_OK</literal>, in which case a <literal>NULL</literal>
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result is returned to the caller instead of an error for an undefined
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object.
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</para>
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<para>
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<programlisting>
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ForeignDataWrapper *
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GetForeignDataWrapper(Oid fdwid);
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</programlisting>
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@@ -1420,6 +1437,23 @@ GetForeignDataWrapper(Oid fdwid);
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<para>
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<programlisting>
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ForeignServer *
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GetForeignServerExtended(Oid serverid, bits16 flags);
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</programlisting>
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This function returns a <structname>ForeignServer</structname> object
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for the foreign server with the given OID. A
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<structname>ForeignServer</structname> object contains properties
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of the server (see <filename>foreign/foreign.h</filename> for details).
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<structfield>flags</structfield> is a bitwise-or'd bit mask indicating
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an extra set of options. It can take the value
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<literal>FSV_MISSING_OK</literal>, in which case a <literal>NULL</literal>
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result is returned to the caller instead of an error for an undefined
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object.
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</para>
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<para>
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<programlisting>
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ForeignServer *
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GetForeignServer(Oid serverid);
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</programlisting>
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‎src/backend/foreign/foreign.c

Copy file name to clipboardExpand all lines: src/backend/foreign/foreign.c
+34-2Lines changed: 34 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -33,6 +33,18 @@
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*/
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ForeignDataWrapper *
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GetForeignDataWrapper(Oid fdwid)
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{
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return GetForeignDataWrapperExtended(fdwid, 0);
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}
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/*
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* GetForeignDataWrapperExtended - look up the foreign-data wrapper
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* by OID. If flags uses FDW_MISSING_OK, return NULL if the object cannot
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* be found instead of raising an error.
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*/
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ForeignDataWrapper *
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GetForeignDataWrapperExtended(Oid fdwid, bits16 flags)
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{
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Form_pg_foreign_data_wrapper fdwform;
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ForeignDataWrapper *fdw;
@@ -43,7 +55,11 @@ GetForeignDataWrapper(Oid fdwid)
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tp = SearchSysCache1(FOREIGNDATAWRAPPEROID, ObjectIdGetDatum(fdwid));
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if (!HeapTupleIsValid(tp))
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elog(ERROR, "cache lookup failed for foreign-data wrapper %u", fdwid);
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{
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if ((flags & FDW_MISSING_OK) == 0)
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elog(ERROR, "cache lookup failed for foreign-data wrapper %u", fdwid);
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return NULL;
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}
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fdwform = (Form_pg_foreign_data_wrapper) GETSTRUCT(tp);
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@@ -91,6 +107,18 @@ GetForeignDataWrapperByName(const char *fdwname, bool missing_ok)
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*/
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ForeignServer *
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GetForeignServer(Oid serverid)
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{
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return GetForeignServerExtended(serverid, 0);
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}
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/*
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* GetForeignServerExtended - look up the foreign server definition. If
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* flags uses FSV_MISSING_OK, return NULL if the object cannot be found
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* instead of raising an error.
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*/
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ForeignServer *
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GetForeignServerExtended(Oid serverid, bits16 flags)
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{
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Form_pg_foreign_server serverform;
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ForeignServer *server;
@@ -101,7 +129,11 @@ GetForeignServer(Oid serverid)
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tp = SearchSysCache1(FOREIGNSERVEROID, ObjectIdGetDatum(serverid));
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if (!HeapTupleIsValid(tp))
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elog(ERROR, "cache lookup failed for foreign server %u", serverid);
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{
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if ((flags & FSV_MISSING_OK) == 0)
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elog(ERROR, "cache lookup failed for foreign server %u", serverid);
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return NULL;
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}
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serverform = (Form_pg_foreign_server) GETSTRUCT(tp);
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‎src/include/foreign/foreign.h

Copy file name to clipboardExpand all lines: src/include/foreign/foreign.h
+10Lines changed: 10 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -68,11 +68,21 @@ typedef struct ForeignTable
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List *options; /* ftoptions as DefElem list */
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} ForeignTable;
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/* Flags for GetForeignServerExtended */
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#define FSV_MISSING_OK 0x01
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/* Flags for GetForeignDataWrapperExtended */
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#define FDW_MISSING_OK 0x01
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extern ForeignServer *GetForeignServer(Oid serverid);
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extern ForeignServer *GetForeignServerExtended(Oid serverid,
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bits16 flags);
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extern ForeignServer *GetForeignServerByName(const char *name, bool missing_ok);
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extern UserMapping *GetUserMapping(Oid userid, Oid serverid);
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extern ForeignDataWrapper *GetForeignDataWrapper(Oid fdwid);
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extern ForeignDataWrapper *GetForeignDataWrapperExtended(Oid fdwid,
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bits16 flags);
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extern ForeignDataWrapper *GetForeignDataWrapperByName(const char *name,
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bool missing_ok);
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extern ForeignTable *GetForeignTable(Oid relid);

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