Allow custom and foreign scans to have shutdown callbacks.

This is expected to be useful mostly when performing such scans in
parallel, because in that case it allows (in combination with commit
acf555bc53acb589b5a2827e65d655fa8c9adee0) nodes below a Gather to get
control just before the DSM segment goes away.

KaiGai Kohei, except that I rewrote the documentation.  Reviewed by
Claudio Freire.

Discussion: http://postgr.es/m/CADyhKSXJK0jUJ8rWv4AmKDhsUh124_rEn39eqgfC5D8fu6xVuw@mail.gmail.com

diff --git a/doc/src/sgml/custom-scan.sgml b/doc/src/sgml/custom-scan.sgml
index 1ca9247124583f5957d2af2623f0892b414de826..6159c3a24ebf09cfe0e96bf9d56534d459628020 100644 (file)
--- a/doc/src/sgml/custom-scan.sgml
+++ b/doc/src/sgml/custom-scan.sgml
@@ -340,6 +340,19 @@ void (*InitializeWorkerCustomScan) (CustomScanState *node,
 
    <para>
 <programlisting>
+void (*ShutdownCustomScan) (CustomScanState *node);
+</programlisting>
+    Release resources when it is anticipated the node will not be executed
+    to completion.  This is not called in all cases; sometimes,
+    <literal>EndCustomScan</> may be called without this function having
+    been called first.  Since the DSM segment used by parallel query is
+    destroyed just after this callback is invoked, custom scan providers that
+    wish to take some action before the DSM segment goes away should implement
+    this method.
+   </para>
+
+   <para>
+<programlisting>
 void (*ExplainCustomScan) (CustomScanState *node,
                            List *ancestors,
                            ExplainState *es);

diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml
index 0c1db070ed88657965c02e16d611e3dc258fa371..dbeaab555db6775624d05a297c4174fcc62292e8 100644 (file)
--- a/doc/src/sgml/fdwhandler.sgml
+++ b/doc/src/sgml/fdwhandler.sgml
@@ -1254,6 +1254,20 @@ InitializeWorkerForeignScan(ForeignScanState *node, shm_toc *toc,
     This callback is optional, and needs only be supplied if this
     custom path supports parallel execution.
    </para>
+
+   <para>
+<programlisting>
+void
+ShutdownForeignScan(ForeignScanState *node);
+</programlisting>
+    Release resources when it is anticipated the node will not be executed
+    to completion.  This is not called in all cases; sometimes,
+    <literal>EndForeignScan</> may be called without this function having
+    been called first.  Since the DSM segment used by parallel query is
+    destroyed just after this callback is invoked, foreign data wrappers that
+    wish to take some action before the DSM segment goes away should implement
+    this method.
+   </para>
    </sect2>
 
    </sect1>

diff --git a/src/backend/executor/execProcnode.c b/src/backend/executor/execProcnode.c
index 5ccc2e846dc981b4c9bd27e869e50de3db297e48..ef6f35a5a0b0f7f717d0b9bc8f026e650cde005b 100644 (file)
--- a/src/backend/executor/execProcnode.c
+++ b/src/backend/executor/execProcnode.c
@@ -822,6 +822,12 @@ ExecShutdownNode(PlanState *node)
                case T_GatherState:
                        ExecShutdownGather((GatherState *) node);
                        break;
+               case T_ForeignScanState:
+                       ExecShutdownForeignScan((ForeignScanState *) node);
+                       break;
+               case T_CustomScanState:
+                       ExecShutdownCustomScan((CustomScanState *) node);
+                       break;
                default:
                        break;
        }

diff --git a/src/backend/executor/nodeCustom.c b/src/backend/executor/nodeCustom.c
index 16343a56df73fa5d83c2359786e03e083007cd8e..d4647482905bb692f7d84541aab6c90e47328ffb 100644 (file)
--- a/src/backend/executor/nodeCustom.c
+++ b/src/backend/executor/nodeCustom.c
@@ -202,3 +202,12 @@ ExecCustomScanInitializeWorker(CustomScanState *node, shm_toc *toc)
                methods->InitializeWorkerCustomScan(node, toc, coordinate);
        }
 }
+
+void
+ExecShutdownCustomScan(CustomScanState *node)
+{
+       const CustomExecMethods *methods = node->methods;
+
+       if (methods->ShutdownCustomScan)
+               methods->ShutdownCustomScan(node);
+}

diff --git a/src/backend/executor/nodeForeignscan.c b/src/backend/executor/nodeForeignscan.c
index 86a77e356c02a250048f6d748fbf20c60ee1c33b..3b6d1390eb41285444a6daa55080984eabace7b9 100644 (file)
--- a/src/backend/executor/nodeForeignscan.c
+++ b/src/backend/executor/nodeForeignscan.c
@@ -353,3 +353,19 @@ ExecForeignScanInitializeWorker(ForeignScanState *node, shm_toc *toc)
                fdwroutine->InitializeWorkerForeignScan(node, toc, coordinate);
        }
 }
+
+/* ----------------------------------------------------------------
+ *             ExecShutdownForeignScan
+ *
+ *             Gives FDW chance to stop asynchronous resource consumption
+ *             and release any resources still held.
+ * ----------------------------------------------------------------
+ */
+void
+ExecShutdownForeignScan(ForeignScanState *node)
+{
+       FdwRoutine *fdwroutine = node->fdwroutine;
+
+       if (fdwroutine->ShutdownForeignScan)
+               fdwroutine->ShutdownForeignScan(node);
+}

diff --git a/src/include/executor/nodeCustom.h b/src/include/executor/nodeCustom.h
index 19d5d047b5cd924749f8532a0ef158ae9f54ad0c..c2f2ca1eede4cea3f811e206dee15272bdf568a4 100644 (file)
--- a/src/include/executor/nodeCustom.h
+++ b/src/include/executor/nodeCustom.h
@@ -37,5 +37,6 @@ extern void ExecCustomScanInitializeDSM(CustomScanState *node,
                                                        ParallelContext *pcxt);
 extern void ExecCustomScanInitializeWorker(CustomScanState *node,
                                                           shm_toc *toc);
+extern void ExecShutdownCustomScan(CustomScanState *node);
 
 #endif   /* NODECUSTOM_H */

diff --git a/src/include/executor/nodeForeignscan.h b/src/include/executor/nodeForeignscan.h
index f0e942a8bcb26fddb41ec921ece2fd1cd595d827..1b167b8143ab201ab9699d87645cdcefd050b79e 100644 (file)
--- a/src/include/executor/nodeForeignscan.h
+++ b/src/include/executor/nodeForeignscan.h
@@ -28,5 +28,6 @@ extern void ExecForeignScanInitializeDSM(ForeignScanState *node,
                                                         ParallelContext *pcxt);
 extern void ExecForeignScanInitializeWorker(ForeignScanState *node,
                                                                shm_toc *toc);
+extern void ExecShutdownForeignScan(ForeignScanState *node);
 
 #endif   /* NODEFOREIGNSCAN_H */

diff --git a/src/include/foreign/fdwapi.h b/src/include/foreign/fdwapi.h
index 523d4155756dfe8827ceb968a95d12e8b5422c9c..6ca44f734f96c682bafc473dc11e87c22b5ff45b 100644 (file)
--- a/src/include/foreign/fdwapi.h
+++ b/src/include/foreign/fdwapi.h
@@ -151,6 +151,7 @@ typedef void (*InitializeDSMForeignScan_function) (ForeignScanState *node,
 typedef void (*InitializeWorkerForeignScan_function) (ForeignScanState *node,
                                                                                                                                shm_toc *toc,
                                                                                                                   void *coordinate);
+typedef void (*ShutdownForeignScan_function) (ForeignScanState *node);
 typedef bool (*IsForeignScanParallelSafe_function) (PlannerInfo *root,
                                                                                                                         RelOptInfo *rel,
                                                                                                                 RangeTblEntry *rte);
@@ -224,6 +225,7 @@ typedef struct FdwRoutine
        EstimateDSMForeignScan_function EstimateDSMForeignScan;
        InitializeDSMForeignScan_function InitializeDSMForeignScan;
        InitializeWorkerForeignScan_function InitializeWorkerForeignScan;
+       ShutdownForeignScan_function ShutdownForeignScan;
 } FdwRoutine;
 
 

diff --git a/src/include/nodes/extensible.h b/src/include/nodes/extensible.h
index 7e860b0dca72ee2788104a891007510896b5ffb7..0b02cc18e99cfb2445abdd8571cf58da5eeb357e 100644 (file)
--- a/src/include/nodes/extensible.h
+++ b/src/include/nodes/extensible.h
@@ -139,6 +139,7 @@ typedef struct CustomExecMethods
        void            (*InitializeWorkerCustomScan) (CustomScanState *node,
                                                                                                                   shm_toc *toc,
                                                                                                                   void *coordinate);
+       void            (*ShutdownCustomScan) (CustomScanState *node);
 
        /* Optional: print additional information in EXPLAIN */
        void            (*ExplainCustomScan) (CustomScanState *node,