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authorTom Lane2017-08-30 21:21:08 +0000
committerTom Lane2017-08-30 21:21:08 +0000
commit04e9678614ec64ad9043174ac99a25b1dc45233a (patch)
tree84374124ceecab08afdf7bd19e12930506076e36 /src/include
parent41b0dd987d44089dc48e9c70024277e253b396b7 (diff)
Code review for nodeGatherMerge.c.
Comment the fields of GatherMergeState, and organize them a bit more sensibly. Comment GMReaderTupleBuffer more usefully too. Improve assorted other comments that were obsolete or just not very good English. Get rid of the use of a GMReaderTupleBuffer for the leader process; that was confusing, since only the "done" field was used, and that in a way redundant with need_to_scan_locally. In gather_merge_init, avoid calling load_tuple_array for already-known-exhausted workers. I'm not sure if there's a live bug there, but the case is unlikely to be well tested due to timing considerations. Remove some useless code, such as duplicating the tts_isempty test done by TupIsNull. Remove useless initialization of ps.qual, replacing that with an assertion that we have no qual to check. (If we did, the code would fail to check it.) Avoid applying heap_copytuple to a null tuple. While that fails to crash, it's confusing and it makes the code less legible not more so IMO. Propagate a couple of these changes into nodeGather.c, as well. Back-patch to v10, partly because of the possibility that the gather_merge_init change is fixing a live bug, but mostly to keep the branches in sync to ease future bug fixes.
Diffstat (limited to 'src/include')
-rw-r--r--src/include/nodes/execnodes.h46
1 files changed, 25 insertions, 21 deletions
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index d1565e74961..6cf128a7f02 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1923,15 +1923,17 @@ typedef struct UniqueState
typedef struct GatherState
{
PlanState ps; /* its first field is NodeTag */
- bool initialized;
- struct ParallelExecutorInfo *pei;
- int nreaders;
- int nextreader;
- int nworkers_launched;
- struct TupleQueueReader **reader;
- TupleTableSlot *funnel_slot;
- bool need_to_scan_locally;
+ bool initialized; /* workers launched? */
+ bool need_to_scan_locally; /* need to read from local plan? */
int64 tuples_needed; /* tuple bound, see ExecSetTupleBound */
+ /* these fields are set up once: */
+ TupleTableSlot *funnel_slot;
+ struct ParallelExecutorInfo *pei;
+ /* all remaining fields are reinitialized during a rescan: */
+ int nworkers_launched; /* original number of workers */
+ int nreaders; /* number of still-active workers */
+ int nextreader; /* next one to try to read from */
+ struct TupleQueueReader **reader; /* array with nreaders active entries */
} GatherState;
/* ----------------
@@ -1942,25 +1944,27 @@ typedef struct GatherState
* merge the results into a single sorted stream.
* ----------------
*/
-struct GMReaderTuple;
+struct GMReaderTupleBuffer; /* private in nodeGatherMerge.c */
typedef struct GatherMergeState
{
PlanState ps; /* its first field is NodeTag */
- bool initialized;
+ bool initialized; /* workers launched? */
+ bool gm_initialized; /* gather_merge_init() done? */
+ bool need_to_scan_locally; /* need to read from local plan? */
+ int64 tuples_needed; /* tuple bound, see ExecSetTupleBound */
+ /* these fields are set up once: */
+ TupleDesc tupDesc; /* descriptor for subplan result tuples */
+ int gm_nkeys; /* number of sort columns */
+ SortSupport gm_sortkeys; /* array of length gm_nkeys */
struct ParallelExecutorInfo *pei;
- int nreaders;
- int nworkers_launched;
- struct TupleQueueReader **reader;
- TupleDesc tupDesc;
- TupleTableSlot **gm_slots;
+ /* all remaining fields are reinitialized during a rescan: */
+ int nworkers_launched; /* original number of workers */
+ int nreaders; /* number of active workers */
+ TupleTableSlot **gm_slots; /* array with nreaders+1 entries */
+ struct TupleQueueReader **reader; /* array with nreaders active entries */
+ struct GMReaderTupleBuffer *gm_tuple_buffers; /* nreaders tuple buffers */
struct binaryheap *gm_heap; /* binary heap of slot indices */
- bool gm_initialized; /* gather merge initilized ? */
- bool need_to_scan_locally;
- int64 tuples_needed; /* tuple bound, see ExecSetTupleBound */
- int gm_nkeys;
- SortSupport gm_sortkeys; /* array of length ms_nkeys */
- struct GMReaderTupleBuffer *gm_tuple_buffers; /* tuple buffer per reader */
} GatherMergeState;
/* ----------------