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Commit9088d1b

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Add GetForeignColumnOptions() to foreign.c, and add some documentation.
GetForeignColumnOptions provides some abstraction for accessingcolumn-specific FDW options, on a par with the access functions that werealready provided here for other FDW-related information.Adjust file_fdw.c to use GetForeignColumnOptions instead of equivalenthand-rolled code.In addition, add some SGML documentation for the functions exported byforeign.c that are meant for use by FDW authors.(This is the fdw_helper portion of the proposed pgsql_fdw patch.)Hanada Shigeru, reviewed by KaiGai Kohei
1 parentcf7026b commit9088d1b

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4 files changed

+154
-39
lines changed

4 files changed

+154
-39
lines changed

‎contrib/file_fdw/file_fdw.c

Lines changed: 12 additions & 37 deletions
Original file line numberDiff line numberDiff line change
@@ -27,7 +27,6 @@
2727
#include"optimizer/cost.h"
2828
#include"optimizer/pathnode.h"
2929
#include"utils/rel.h"
30-
#include"utils/syscache.h"
3130

3231
PG_MODULE_MAGIC;
3332

@@ -346,54 +345,30 @@ get_file_fdw_attribute_options(Oid relid)
346345
/* Retrieve FDW options for all user-defined attributes. */
347346
for (attnum=1;attnum <=natts;attnum++)
348347
{
349-
HeapTupletuple;
350-
Form_pg_attributeattr;
351-
Datumdatum;
352-
boolisnull;
348+
Form_pg_attributeattr=tupleDesc->attrs[attnum-1];
349+
List*options;
350+
ListCell*lc;
353351

354352
/* Skip dropped attributes. */
355-
if (tupleDesc->attrs[attnum-1]->attisdropped)
353+
if (attr->attisdropped)
356354
continue;
357355

358-
/*
359-
* We need the whole pg_attribute tuple not just what is in the
360-
* tupleDesc, so must do a catalog lookup.
361-
*/
362-
tuple=SearchSysCache2(ATTNUM,
363-
RelationGetRelid(rel),
364-
Int16GetDatum(attnum));
365-
if (!HeapTupleIsValid(tuple))
366-
elog(ERROR,"cache lookup failed for attribute %d of relation %u",
367-
attnum,RelationGetRelid(rel));
368-
attr= (Form_pg_attribute)GETSTRUCT(tuple);
369-
370-
datum=SysCacheGetAttr(ATTNUM,
371-
tuple,
372-
Anum_pg_attribute_attfdwoptions,
373-
&isnull);
374-
if (!isnull)
356+
options=GetForeignColumnOptions(relid,attnum);
357+
foreach(lc,options)
375358
{
376-
List*options=untransformRelOptions(datum);
377-
ListCell*lc;
359+
DefElem*def= (DefElem*)lfirst(lc);
378360

379-
foreach(lc,options)
361+
if (strcmp(def->defname,"force_not_null")==0)
380362
{
381-
DefElem*def= (DefElem*)lfirst(lc);
382-
383-
if (strcmp(def->defname,"force_not_null")==0)
363+
if (defGetBoolean(def))
384364
{
385-
if (defGetBoolean(def))
386-
{
387-
char*attname=pstrdup(NameStr(attr->attname));
365+
char*attname=pstrdup(NameStr(attr->attname));
388366

389-
fnncolumns=lappend(fnncolumns,makeString(attname));
390-
}
367+
fnncolumns=lappend(fnncolumns,makeString(attname));
391368
}
392-
/* maybe in future handle other options here */
393369
}
370+
/* maybe in future handle other options here */
394371
}
395-
396-
ReleaseSysCache(tuple);
397372
}
398373

399374
heap_close(rel,AccessShareLock);

‎doc/src/sgml/fdwhandler.sgml

Lines changed: 105 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -244,4 +244,109 @@ EndForeignScan (ForeignScanState *node);
244244

245245
</sect1>
246246

247+
<sect1 id="fdw-helpers">
248+
<title>Foreign Data Wrapper Helper Functions</title>
249+
250+
<para>
251+
Several helper functions are exported from the core server so that
252+
authors of foreign data wrappers can get easy access to attributes of
253+
FDW-related objects, such as FDW options.
254+
To use any of these functions, you need to include the header file
255+
<filename>foreign/foreign.h</filename> in your source file.
256+
That header also defines the struct types that are returned by
257+
these functions.
258+
</para>
259+
260+
<para>
261+
<programlisting>
262+
ForeignDataWrapper *
263+
GetForeignDataWrapper(Oid fdwid);
264+
</programlisting>
265+
266+
This function returns a <structname>ForeignDataWrapper</structname>
267+
object for the foreign-data wrapper with the given OID. A
268+
<structname>ForeignDataWrapper</structname> object contains properties
269+
of the FDW (see <filename>foreign/foreign.h</filename> for details).
270+
</para>
271+
272+
<para>
273+
<programlisting>
274+
ForeignServer *
275+
GetForeignServer(Oid serverid);
276+
</programlisting>
277+
278+
This function returns a <structname>ForeignServer</structname> object
279+
for the foreign server with the given OID. A
280+
<structname>ForeignServer</structname> object contains properties
281+
of the server (see <filename>foreign/foreign.h</filename> for details).
282+
</para>
283+
284+
<para>
285+
<programlisting>
286+
UserMapping *
287+
GetUserMapping(Oid userid, Oid serverid);
288+
</programlisting>
289+
290+
This function returns a <structname>UserMapping</structname> object for
291+
the user mapping of the given role on the given server. (If there is no
292+
mapping for the specific user, it will return the mapping for
293+
<literal>PUBLIC</>, or throw error if there is none.) A
294+
<structname>UserMapping</structname> object contains properties of the
295+
user mapping (see <filename>foreign/foreign.h</filename> for details).
296+
</para>
297+
298+
<para>
299+
<programlisting>
300+
ForeignTable *
301+
GetForeignTable(Oid relid);
302+
</programlisting>
303+
304+
This function returns a <structname>ForeignTable</structname> object for
305+
the foreign table with the given OID. A
306+
<structname>ForeignTable</structname> object contains properties of the
307+
foreign table (see <filename>foreign/foreign.h</filename> for details).
308+
</para>
309+
310+
<para>
311+
<programlisting>
312+
List *
313+
GetForeignTableColumnOptions(Oid relid, AttrNumber attnum);
314+
</programlisting>
315+
316+
This function returns the per-column FDW options for the column with the
317+
given foreign table OID and attribute number, in the form of a list of
318+
<structname>DefElem</structname>. NIL is returned if the column has no
319+
options.
320+
</para>
321+
322+
<para>
323+
Some object types have name-based lookup functions in addition to the
324+
OID-based ones:
325+
</para>
326+
327+
<para>
328+
<programlisting>
329+
ForeignDataWrapper *
330+
GetForeignDataWrapperByName(const char *name, bool missing_ok);
331+
</programlisting>
332+
333+
This function returns a <structname>ForeignDataWrapper</structname>
334+
object for the foreign-data wrapper with the given name. If the wrapper
335+
is not found, return NULL if missing_ok is true, otherwise raise an
336+
error.
337+
</para>
338+
339+
<para>
340+
<programlisting>
341+
ForeignServer *
342+
GetForeignServerByName(const char *name, bool missing_ok);
343+
</programlisting>
344+
345+
This function returns a <structname>ForeignServer</structname> object
346+
for the foreign server with the given name. If the server is not found,
347+
return NULL if missing_ok is true, otherwise raise an error.
348+
</para>
349+
350+
</sect1>
351+
247352
</chapter>

‎src/backend/foreign/foreign.c

Lines changed: 35 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -28,7 +28,6 @@ extern Datum pg_options_to_table(PG_FUNCTION_ARGS);
2828
externDatumpostgresql_fdw_validator(PG_FUNCTION_ARGS);
2929

3030

31-
3231
/*
3332
* GetForeignDataWrapper -look up the foreign-data wrapper by OID.
3433
*/
@@ -71,7 +70,6 @@ GetForeignDataWrapper(Oid fdwid)
7170
}
7271

7372

74-
7573
/*
7674
* GetForeignDataWrapperByName - look up the foreign-data wrapper
7775
* definition by name.
@@ -247,6 +245,39 @@ GetForeignTable(Oid relid)
247245
}
248246

249247

248+
/*
249+
* GetForeignColumnOptions - Get attfdwoptions of given relation/attnum
250+
* as list of DefElem.
251+
*/
252+
List*
253+
GetForeignColumnOptions(Oidrelid,AttrNumberattnum)
254+
{
255+
List*options;
256+
HeapTupletp;
257+
Datumdatum;
258+
boolisnull;
259+
260+
tp=SearchSysCache2(ATTNUM,
261+
ObjectIdGetDatum(relid),
262+
Int16GetDatum(attnum));
263+
if (!HeapTupleIsValid(tp))
264+
elog(ERROR,"cache lookup failed for attribute %d of relation %u",
265+
attnum,relid);
266+
datum=SysCacheGetAttr(ATTNUM,
267+
tp,
268+
Anum_pg_attribute_attfdwoptions,
269+
&isnull);
270+
if (isnull)
271+
options=NIL;
272+
else
273+
options=untransformRelOptions(datum);
274+
275+
ReleaseSysCache(tp);
276+
277+
returnoptions;
278+
}
279+
280+
250281
/*
251282
* GetFdwRoutine - call the specified foreign-data wrapper handler routine
252283
* to get its FdwRoutine struct.
@@ -498,6 +529,7 @@ postgresql_fdw_validator(PG_FUNCTION_ARGS)
498529
PG_RETURN_BOOL(true);
499530
}
500531

532+
501533
/*
502534
* get_foreign_data_wrapper_oid - given a FDW name, look up the OID
503535
*
@@ -518,6 +550,7 @@ get_foreign_data_wrapper_oid(const char *fdwname, bool missing_ok)
518550
returnoid;
519551
}
520552

553+
521554
/*
522555
* get_foreign_server_oid - given a FDW name, look up the OID
523556
*

‎src/include/foreign/foreign.h

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -76,6 +76,8 @@ extern ForeignDataWrapper *GetForeignDataWrapperByName(const char *name,
7676
boolmissing_ok);
7777
externForeignTable*GetForeignTable(Oidrelid);
7878

79+
externList*GetForeignColumnOptions(Oidrelid,AttrNumberattnum);
80+
7981
externOidget_foreign_data_wrapper_oid(constchar*fdwname,boolmissing_ok);
8082
externOidget_foreign_server_oid(constchar*servername,boolmissing_ok);
8183

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