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Add optimizer and executor support for parallel index scans.

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In combination with 569174f1be, which
taught the btree AM how to perform parallel index scans, this allows
parallel index scan plans on btree indexes.  This infrastructure
should be general enough to support parallel index scans for other
index AMs as well, if someone updates them to support parallel
scans.

Amit Kapila, reviewed and tested by Anastasia Lubennikova, Tushar
Ahuja, and Haribabu Kommi, and me.
This commit is contained in:
Robert Haas
2017-02-15 13:53:24 -05:00
parent 51ee6f3160
commit 5262f7a4fc
29 changed files with 366 additions and 55 deletions
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67
src/backend/optimizer/path/indxpath.c
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@@ -813,7 +813,7 @@ get_index_paths(PlannerInfo *root, RelOptInfo *rel,
/*
* build_index_paths
* Given an index and a set of index clauses for it, construct zero
* or more IndexPaths.
* or more IndexPaths. It also constructs zero or more partial IndexPaths.
*
* We return a list of paths because (1) this routine checks some cases
* that should cause us to not generate any IndexPath, and (2) in some
@@ -1042,8 +1042,41 @@ build_index_paths(PlannerInfo *root, RelOptInfo *rel,
NoMovementScanDirection,
index_only_scan,
outer_relids,
loop_count);
loop_count,
false);
result = lappend(result, ipath);
/*
* If appropriate, consider parallel index scan. We don't allow
* parallel index scan for bitmap or index only scans.
*/
if (index->amcanparallel && !index_only_scan &&
rel->consider_parallel && outer_relids == NULL &&
scantype != ST_BITMAPSCAN)
{
ipath = create_index_path(root, index,
index_clauses,
clause_columns,
orderbyclauses,
orderbyclausecols,
useful_pathkeys,
index_is_ordered ?
ForwardScanDirection :
NoMovementScanDirection,
index_only_scan,
outer_relids,
loop_count,
true);
/*
* if, after costing the path, we find that it's not worth
* using parallel workers, just free it.
*/
if (ipath->path.parallel_workers > 0)
add_partial_path(rel, (Path *) ipath);
else
pfree(ipath);
}
}
/*
@@ -1066,8 +1099,36 @@ build_index_paths(PlannerInfo *root, RelOptInfo *rel,
BackwardScanDirection,
index_only_scan,
outer_relids,
loop_count);
loop_count,
false);
result = lappend(result, ipath);
/* If appropriate, consider parallel index scan */
if (index->amcanparallel && !index_only_scan &&
rel->consider_parallel && outer_relids == NULL &&
scantype != ST_BITMAPSCAN)
{
ipath = create_index_path(root, index,
index_clauses,
clause_columns,
NIL,
NIL,
useful_pathkeys,
BackwardScanDirection,
index_only_scan,
outer_relids,
loop_count,
true);
/*
* if, after costing the path, we find that it's not worth
* using parallel workers, just free it.
*/
if (ipath->path.parallel_workers > 0)
add_partial_path(rel, (Path *) ipath);
else
pfree(ipath);
}
}
}