Do COPY FROM to foreign parts only when needed.

That is, when
1) pg_pathman was compiled against postgres with shardman patches.
2) Shardman's COPY FROM was explicitly asked by setting renderzvous var.

Also, check for 'freeze' option early, as before, to keep regression tests as
they are.

Author: arssher

src/utility_stmt_hooking.c

@@ -22,6 +22,7 @@
 #include "access/xact.h"
 #include "catalog/namespace.h"
 #include "commands/copy.h"
+#include "commands/defrem.h"
 #include "commands/trigger.h"
 #include "commands/tablecmds.h"
 #include "foreign/fdwapi.h"
@@ -105,6 +106,26 @@ is_pathman_related_copy(Node *parsetree)
 	/* Check that relation is partitioned */
 	if (get_pathman_relation_info(parent_relid))
 	{
+		ListCell *lc;
+
+		/* Analyze options list */
+		foreach (lc, copy_stmt->options)
+		{
+			DefElem *defel = lfirst_node(DefElem, lc);
+
+			/* We do not support freeze */
+			/*
+			 * It would be great to allow copy.c extract option value and
+			 * check it ready. However, there is no possibility (hooks) to do
+			 * that before messaging 'ok, begin streaming data' to the client,
+			 * which is ugly and confusing: e.g. it would require us to
+			 * actually send something in regression tests before we notice
+			 * the error.
+			 */
+			if (strcmp(defel->defname, "freeze") == 0 && defGetBoolean(defel))
+				elog(ERROR, "freeze is not supported for partitioned tables");
+		}
+
 		/* Emit ERROR if we can't see the necessary symbols */
 		#ifdef DISABLE_PATHMAN_COPY
 			elog(ERROR, "COPY is not supported for partitioned tables on Windows");
@@ -467,11 +488,6 @@ PathmanCopyFrom(CopyState cstate, Relation parent_rel,
 
 	uint64				processed = 0;
 
-	/* We do not support freeze */
-	if (cstate->freeze)
-		elog(ERROR, "freeze is not supported for partitioned tables");
-
-
 	tupDesc = RelationGetDescr(parent_rel);
 
 	parent_result_rel = makeNode(ResultRelInfo);
@@ -633,11 +649,13 @@ PathmanCopyFrom(CopyState cstate, Relation parent_rel,
 					recheckIndexes = ExecInsertIndexTuples(slot, &(tuple->t_self),
 														   estate, false, NULL, NIL);
 			}
+#ifdef PG_SHARDMAN
 			else /* FDW table */
 			{
 				child_result_rel->ri_FdwRoutine->ForeignNextCopyFrom(
 					estate, child_result_rel, cstate);
 			}
+#endif
 
 			/* AFTER ROW INSERT Triggers (FIXME: NULL transition) */
 			ExecARInsertTriggersCompat(estate, child_result_rel, tuple,
@@ -694,25 +712,51 @@ prepare_rri_for_copy(ResultRelInfoHolder *rri_holder,
 {
 	ResultRelInfo	*rri = rri_holder->result_rel_info;
 	FdwRoutine		*fdw_routine = rri->ri_FdwRoutine;
-	CopyState		cstate = (CopyState) rps_storage->callback_arg;
-	ResultRelInfo	*parent_rri;
-	const char		*parent_relname;
-	EState		   *estate;
-
-	estate = rps_storage->estate;
 
 	if (fdw_routine != NULL)
 	{
-		parent_rri = rps_storage->saved_rel_info;
-		parent_relname = psprintf(
-			"%s.%s", "public",
-			quote_identifier(RelationGetRelationName(parent_rri->ri_RelationDesc)));
-		if (!FdwCopyFromIsSupported(fdw_routine))
-			ereport(ERROR,
-					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-					 errmsg("FDW adapter for relation \"%s\" doesn't support COPY FROM",
-							RelationGetRelationName(rri->ri_RelationDesc))));
-		fdw_routine->BeginForeignCopyFrom(estate, rri, cstate, parent_relname);
+		/*
+		 * If this Postgres has no idea about shardman, behave as usual:
+		 * vanilla Postgres doesn't support COPY FROM to foreign partitions.
+		 * However, shardman patches to core extend FDW API to allow it,
+		 * though currently postgres_fdw does so in a bit perverted way: we
+		 * redirect COPY FROM to parent table on foreign server, assuming it
+		 * exists, and let it direct tuple to proper partition. This is
+		 * because otherwise we have to modify logic of managing connections
+		 * in postgres_fdw and keep many connections open to one server from
+		 * one backend.
+		 */
+#ifndef PG_SHARDMAN
+		goto bail_out; /* to avoid 'unused label' warning */
+#else
+		{ /* separate block to avoid 'unused var' warnings */
+			CopyState		cstate = (CopyState) rps_storage->callback_arg;
+			ResultRelInfo	*parent_rri;
+			const char		*parent_relname;
+			EState		   	*estate;
+
+			/* shardman COPY FROM requested? */
+			if (*find_rendezvous_variable(
+					"shardman_pathman_copy_from_rendezvous") == NULL)
+				goto bail_out;
+
+			estate = rps_storage->estate;
+			parent_rri = rps_storage->saved_rel_info;
+			parent_relname = psprintf(
+				"%s.%s", "public",
+				quote_identifier(RelationGetRelationName(parent_rri->ri_RelationDesc)));
+			if (!FdwCopyFromIsSupported(fdw_routine))
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("FDW adapter for relation \"%s\" doesn't support COPY FROM",
+								RelationGetRelationName(rri->ri_RelationDesc))));
+			fdw_routine->BeginForeignCopyFrom(estate, rri, cstate, parent_relname);
+			return;
+		}
+#endif
+bail_out:
+		elog(ERROR, "cannot copy to foreign partition \"%s\"",
+			 get_rel_name(RelationGetRelid(rri->ri_RelationDesc)));
 	}
 }
 
@@ -723,13 +767,15 @@ static void
 finish_rri_copy(ResultRelInfoHolder *rri_holder,
 				const ResultPartsStorage *rps_storage)
 {
+#ifdef PG_SHARDMAN
 	ResultRelInfo *resultRelInfo = rri_holder->result_rel_info;
 
 	if (resultRelInfo->ri_FdwRoutine)
 	{
 		resultRelInfo->ri_FdwRoutine->EndForeignCopyFrom(
 			rps_storage->estate, resultRelInfo);
 	}
+#endif
 }
 
 /*