Expose ogr_fdw_info functions via SQL

README.md

@@ -426,6 +426,43 @@ ALTER SERVER myserver_latin1
 	);
 ```
 
+### FDW Reflection
+
+To view all GDAL table names available from a FDW server (the SQL equivalent of `ogr_fdw_info -s {datasource}`):
+
+```sql
+SELECT ogr_fdw_layers('myserver');
+```
+```
+ ogr_fdw_layers
+----------------
+ Cities
+ Countries
+
+(2 rows)
+```
+
+To retrieve the `CREATE FOREIGN TABLE` SQL for a particular OGR layer as the SQL equivalent of `ogr_fdw_info -s {datasource} -l {layer}`, use the `ogr_fdw_table_sql(server_name, ogr_layer_name, table_name=NULL, launder_column_names=TRUE, launder_table_name=TRUE)` function. By default the table name will reflect the OGR layer name. `launder_column_names` and `launder_table_name` have the same meaning as described in [Mixed Case and Special Characters](#mixed-case-and-special-characters).
+
+```sql
+SELECT ogr_fdw_table_sql('myserver', 'pt_two');
+```
+```
+        ogr_fdw_table_sql
+---------------------------------
+CREATE FOREIGN TABLE "pt_two" (
+  fid integer,
+  "geom" geometry(Point, 4326),
+  "name" varchar,
+  "age" integer,
+  "height" real,
+  "birthdate" date
+) SERVER "myserver"
+OPTIONS (layer 'pt_two');
+
+(1 row)
+```
+
 ### Utility Functions
 
 To view the current FDW and GDAL version.

input/import.source

@@ -3,6 +3,11 @@ set client_min_messages=NOTICE;
 
 CREATE SCHEMA imp1;
 
+SELECT ogr_fdw_layers('myserver');
+
+SELECT ogr_fdw_table_sql('myserver', '2launder');
+SELECT ogr_fdw_table_sql('myserver', '2launder', NULL, FALSE, FALSE);
+
 IMPORT FOREIGN SCHEMA ogr_all 
   LIMIT TO (n2launder) 
   FROM SERVER myserver 
@@ -23,6 +28,8 @@ SELECT * FROM imp1.n2launder WHERE fid = 0;
 
 CREATE SCHEMA imp2;
 
+SELECT ogr_fdw_table_sql('myserver', 'natural', 'naturally');
+
 IMPORT FOREIGN SCHEMA ogr_all 
   LIMIT TO ("natural") 
   FROM SERVER myserver 
@@ -47,6 +54,8 @@ CREATE SERVER svr_test_apost
 
 CREATE SCHEMA imp3;
 
+SELECT ogr_fdw_table_sql('svr_test_apost', 'no_geom_apost');
+
 IMPORT FOREIGN SCHEMA ogr_all 
   LIMIT TO (no_geom_apost) 
   FROM SERVER svr_test_apost

ogr_fdw--1.1.sql

@@ -30,3 +30,17 @@ CREATE OR REPLACE FUNCTION ogr_fdw_drivers()
 	LANGUAGE 'c'
 	IMMUTABLE STRICT
 	PARALLEL SAFE;
+
+CREATE OR REPLACE FUNCTION ogr_fdw_table_sql(server_name text, layer_name text, table_name text DEFAULT NULL, launder_column_names boolean DEFAULT TRUE, launder_table_name boolean DEFAULT TRUE)
+	RETURNS text
+	AS 'MODULE_PATHNAME', 'ogr_fdw_table_sql'
+	LANGUAGE 'c'
+	STABLE
+	PARALLEL SAFE;
+
+CREATE OR REPLACE FUNCTION ogr_fdw_layers(server_name text)
+	RETURNS TABLE (layer_name text)
+	AS 'MODULE_PATHNAME', 'ogr_fdw_layers'
+	LANGUAGE 'c'
+	IMMUTABLE STRICT
+	PARALLEL SAFE;

ogr_fdw.c

@@ -507,7 +507,7 @@ ogrEreportError(const char* errstr)
  * Make sure the datasource is cleaned up when we're done
  * with a connection.
  */
-static void
+void
 ogrFinishConnection(OgrConnection* ogr)
 {
 	elog(DEBUG3, "%s: entered function", __func__);
@@ -525,7 +525,7 @@ ogrFinishConnection(OgrConnection* ogr)
 	ogr->ds = NULL;
 }
 
-static OgrConnection
+OgrConnection
 ogrGetConnectionFromServer(Oid foreignserverid, OgrUpdateable updateable)
 {
 	ForeignServer* server;

ogr_fdw.h

@@ -208,4 +208,7 @@ bool ogrDeparse(StringInfo buf, PlannerInfo* root, RelOptInfo* foreignrel, List*
 Oid ogrGetGeometryOid(void);
 OGRErr pgDatumToOgrGeometry (Datum pg_geometry, Oid pgsendfunc, OGRGeometryH* ogr_geometry);
 
+OgrConnection ogrGetConnectionFromServer(Oid foreignserverid, OgrUpdateable updateable);
+void ogrFinishConnection(OgrConnection* ogr);
+
 #endif /* _OGR_FDW_H */

ogr_fdw_func.c

@@ -11,6 +11,7 @@
 
 #include "ogr_fdw.h"
 #include "ogr_fdw_gdal.h"
+#include "ogr_fdw_common.h"
 
 #include <postgres.h>
 #include <fmgr.h>
@@ -85,4 +86,111 @@ Datum ogr_fdw_version(PG_FUNCTION_ARGS)
 	PG_RETURN_TEXT_P(cstring_to_text(ver_str));
 }
 
+/**
+*/
+Datum ogr_fdw_table_sql(PG_FUNCTION_ARGS);
+PG_FUNCTION_INFO_V1(ogr_fdw_table_sql);
+Datum ogr_fdw_table_sql(PG_FUNCTION_ARGS)
+{
+	char *serverName;
+	char *layerName;
+	char *tableName = NULL;
+	bool launderColumnNames;
+	bool launderTableName;
+
+	ForeignServer* server;
+	OgrConnection ogr;
+	OGRErr err;
+	OGRLayerH ogrLayer;
+	stringbuffer_t buf;
+
+	// because we accept NULL for tableName, we need to make the function
+	// non-STRICT and check all the arguments for NULL
+	if (PG_ARGISNULL(0) || PG_ARGISNULL(1) || PG_ARGISNULL(3) || PG_ARGISNULL(4))
+	{
+		PG_RETURN_NULL();
+	}
+	if (!PG_ARGISNULL(2))
+	{
+		tableName = text_to_cstring(PG_GETARG_TEXT_PP(2));
+	}
+
+	serverName = text_to_cstring(PG_GETARG_TEXT_PP(0));
+	layerName = text_to_cstring(PG_GETARG_TEXT_PP(1));
+	launderColumnNames = PG_GETARG_BOOL(3);
+	launderTableName = PG_GETARG_BOOL(4);
+
+	server = GetForeignServerByName(serverName, false);
+	ogr = ogrGetConnectionFromServer(server->serverid, OGR_UPDATEABLE_FALSE);
+
+	ogrLayer = GDALDatasetGetLayerByName(ogr.ds, layerName);
+	if (ogrLayer)
+	{
+		stringbuffer_init(&buf);
+		err = ogrLayerToSQL(ogrLayer,
+							serverName,
+							launderTableName,
+							launderColumnNames,
+							tableName,
+							ogrGetGeometryOid() != BYTEAOID,
+							&buf);
+
+		if (err != OGRERR_NONE)
+		{
+			ereport(ERROR,
+				(errcode(ERRCODE_FDW_ERROR),
+				errmsg("Cannot generate SQL for: %s", layerName),
+				errhint("GDAL Error %d: %s", CPLGetLastErrorNo(), CPLGetLastErrorMsg())));
+		}
+
+		ogrFinishConnection(&ogr);
+
+		PG_RETURN_TEXT_P(cstring_to_text(stringbuffer_getstring(&buf)));
+	}
+	else
+	{
+		ereport(ERROR,
+			(errcode(ERRCODE_FDW_TABLE_NOT_FOUND),
+			errmsg("Unable to find OGR Layer: %s", layerName)));
+	}
+}
+
+
+/**
+*/
+Datum ogr_fdw_layers(PG_FUNCTION_ARGS);
+PG_FUNCTION_INFO_V1(ogr_fdw_layers);
+Datum ogr_fdw_layers(PG_FUNCTION_ARGS)
+{
+	ForeignServer* server = GetForeignServerByName(text_to_cstring(PG_GETARG_TEXT_PP(0)), false);
+	OgrConnection ogr = ogrGetConnectionFromServer(server->serverid, OGR_UPDATEABLE_FALSE);
+
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+	InitMaterializedSRF(fcinfo, MAT_SRF_USE_EXPECTED_DESC);
 
+	for (int i = 0; i < GDALDatasetGetLayerCount(ogr.ds); i++)
+	{
+		OGRLayerH ogrLayer = GDALDatasetGetLayer(ogr.ds, i);
+
+		if (!ogrLayer)
+		{
+			ereport(WARNING,
+				(errcode(ERRCODE_FDW_ERROR),
+				errmsg("Skipping OGR layer %d, unable to read layer", i),
+				errhint("GDAL Error %d: %s", CPLGetLastErrorNo(), CPLGetLastErrorMsg())));
+			continue;
+		}
+
+		Datum		values[1];
+		bool		nulls[1];
+
+		memset(values, 0, sizeof(values));
+		memset(nulls, 0, sizeof(nulls));
+
+		values[0] = CStringGetTextDatum(OGR_L_GetName(ogrLayer));
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+	}
+	ogrFinishConnection(&ogr);
+
+	return (Datum) 0;
+}

output/import.source

@@ -1,6 +1,46 @@
 set client_min_messages=NOTICE;
 ------------------------------------------------
 CREATE SCHEMA imp1;
+SELECT ogr_fdw_layers('myserver');
+ ogr_fdw_layers 
+----------------
+ enc
+ pt_two
+ 2launder
+ poly
+ natural
+(5 rows)
+
+SELECT ogr_fdw_table_sql('myserver', '2launder');
+                 ogr_fdw_table_sql                  
+----------------------------------------------------
+ CREATE FOREIGN TABLE n2launder (                  +
+   fid bigint,                                     +
+   geom bytea,                                     +
+   n2ame varchar(50) OPTIONS (column_name '2ame'), +
+   age integer,                                    +
+   height double precision,                        +
+   b_rthdate date OPTIONS (column_name 'b-rthdate')+
+ ) SERVER myserver                                 +
+ OPTIONS (layer '2launder');                       +
+
+(1 row)
+
+SELECT ogr_fdw_table_sql('myserver', '2launder', NULL, FALSE, FALSE);
+         ogr_fdw_table_sql         
+-----------------------------------
+ CREATE FOREIGN TABLE "2launder" (+
+   fid bigint,                    +
+   geom bytea,                    +
+   "2ame" varchar(50),            +
+   age integer,                   +
+   "Height" double precision,     +
+   "b-rthdate" date               +
+ ) SERVER myserver                +
+ OPTIONS (layer '2launder');      +
+
+(1 row)
+
 IMPORT FOREIGN SCHEMA ogr_all 
   LIMIT TO (n2launder) 
   FROM SERVER myserver 
@@ -31,6 +71,18 @@ SELECT * FROM imp1.n2launder WHERE fid = 0;
 
 ------------------------------------------------
 CREATE SCHEMA imp2;
+SELECT ogr_fdw_table_sql('myserver', 'natural', 'naturally');
+        ogr_fdw_table_sql         
+----------------------------------
+ CREATE FOREIGN TABLE naturally (+
+   fid bigint,                   +
+   id double precision,          +
+   "natural" varchar(4)          +
+ ) SERVER myserver               +
+ OPTIONS (layer 'natural');      +
+
+(1 row)
+
 IMPORT FOREIGN SCHEMA ogr_all 
   LIMIT TO ("natural") 
   FROM SERVER myserver 
@@ -64,6 +116,19 @@ CREATE SERVER svr_test_apost
     datasource '@abs_srcdir@/data/no_geom_apost.csv',
     format 'CSV' );
 CREATE SCHEMA imp3;
+SELECT ogr_fdw_table_sql('svr_test_apost', 'no_geom_apost');
+                        ogr_fdw_table_sql                         
+------------------------------------------------------------------
+ CREATE FOREIGN TABLE no_geom_apost (                            +
+   fid bigint,                                                   +
+   name varchar,                                                 +
+   age varchar,                                                  +
+   person_s_value varchar OPTIONS (column_name 'person''s value')+
+ ) SERVER svr_test_apost                                         +
+ OPTIONS (layer 'no_geom_apost');                                +
+
+(1 row)
+
 IMPORT FOREIGN SCHEMA ogr_all 
   LIMIT TO (no_geom_apost) 
   FROM SERVER svr_test_apost