diff options
Diffstat (limited to 'src/include')
| -rw-r--r-- | src/include/nodes/plannodes.h | 15 | ||||
| -rw-r--r-- | src/include/nodes/relation.h | 6 |
2 files changed, 15 insertions, 6 deletions
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h index 7c51e7f9d21..a382331f419 100644 --- a/src/include/nodes/plannodes.h +++ b/src/include/nodes/plannodes.h @@ -825,13 +825,21 @@ typedef struct Unique /* ------------ * gather node + * + * Note: rescan_param is the ID of a PARAM_EXEC parameter slot. That slot + * will never actually contain a value, but the Gather node must flag it as + * having changed whenever it is rescanned. The child parallel-aware scan + * nodes are marked as depending on that parameter, so that the rescan + * machinery is aware that their output is likely to change across rescans. + * In some cases we don't need a rescan Param, so rescan_param is set to -1. * ------------ */ typedef struct Gather { Plan plan; - int num_workers; - bool single_copy; + int num_workers; /* planned number of worker processes */ + int rescan_param; /* ID of Param that signals a rescan, or -1 */ + bool single_copy; /* don't execute plan more than once */ bool invisible; /* suppress EXPLAIN display (for testing)? */ } Gather; @@ -842,7 +850,8 @@ typedef struct Gather typedef struct GatherMerge { Plan plan; - int num_workers; + int num_workers; /* planned number of worker processes */ + int rescan_param; /* ID of Param that signals a rescan, or -1 */ /* remaining fields are just like the sort-key info in struct Sort */ int numCols; /* number of sort-key columns */ AttrNumber *sortColIdx; /* their indexes in the target list */ diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h index 3ccc9d1b037..a39e59d8ac9 100644 --- a/src/include/nodes/relation.h +++ b/src/include/nodes/relation.h @@ -1268,9 +1268,9 @@ typedef struct GatherPath } GatherPath; /* - * GatherMergePath runs several copies of a plan in parallel and - * collects the results. For gather merge parallel leader always execute the - * plan. + * GatherMergePath runs several copies of a plan in parallel and collects + * the results, preserving their common sort order. For gather merge, the + * parallel leader always executes the plan too, so we don't need single_copy. */ typedef struct GatherMergePath { |