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Fix up planner infrastructure to support LATERAL properly.

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This patch takes care of a number of problems having to do with failure
to choose valid join orders and incorrect handling of lateral references
pulled up from subqueries.  Notable changes:

* Add a LateralJoinInfo data structure similar to SpecialJoinInfo, to
represent join ordering constraints created by lateral references.
(I first considered extending the SpecialJoinInfo structure, but the
semantics are different enough that a separate data structure seems
better.)  Extend join_is_legal() and related functions to prevent trying
to form unworkable joins, and to ensure that we will consider joins that
satisfy lateral references even if the joins would be clauseless.

* Fill in the infrastructure needed for the last few types of relation scan
paths to support parameterization.  We'd have wanted this eventually
anyway, but it is necessary now because a relation that gets pulled up out
of a UNION ALL subquery may acquire a reltargetlist containing lateral
references, meaning that its paths *have* to be parameterized whether or
not we have any code that can push join quals down into the scan.

* Compute data about lateral references early in query_planner(), and save
in RelOptInfo nodes, to avoid repetitive calculations later.

* Assorted corner-case bug fixes.

There's probably still some bugs left, but this is a lot closer to being
real than it was before.
This commit is contained in:
Tom Lane
2012-08-26 22:48:55 -04:00
parent de87d47044
commit 9ff79b9d4e
30 changed files with 818 additions and 183 deletions
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28
src/backend/optimizer/util/relnode.c
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@ -109,6 +109,8 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptKind reloptkind)
rel->relid = relid;
rel->rtekind = rte->rtekind;
/* min_attr, max_attr, attr_needed, attr_widths are set below */
rel->lateral_vars = NIL;
rel->lateral_relids = NULL;
rel->indexlist = NIL;
rel->pages = 0;
rel->tuples = 0;
@ -365,6 +367,8 @@ build_join_rel(PlannerInfo *root,
joinrel->max_attr = 0;
joinrel->attr_needed = NULL;
joinrel->attr_widths = NULL;
joinrel->lateral_vars = NIL;
joinrel->lateral_relids = NULL;
joinrel->indexlist = NIL;
joinrel->pages = 0;
joinrel->tuples = 0;
@ -472,8 +476,7 @@ build_joinrel_tlist(PlannerInfo *root, RelOptInfo *joinrel,
foreach(vars, input_rel->reltargetlist)
{
Node *origvar = (Node *) lfirst(vars);
Var *var;
Var *var = (Var *) lfirst(vars);
RelOptInfo *baserel;
int ndx;
@ -481,22 +484,17 @@ build_joinrel_tlist(PlannerInfo *root, RelOptInfo *joinrel,
* Ignore PlaceHolderVars in the input tlists; we'll make our own
* decisions about whether to copy them.
*/
if (IsA(origvar, PlaceHolderVar))
if (IsA(var, PlaceHolderVar))
continue;
/*
* We can't run into any child RowExprs here, but we could find a
* whole-row Var with a ConvertRowtypeExpr atop it.
* Otherwise, anything in a baserel or joinrel targetlist ought to be
* a Var. (More general cases can only appear in appendrel child
* rels, which will never be seen here.)
*/
var = (Var *) origvar;
while (!IsA(var, Var))
{
if (IsA(var, ConvertRowtypeExpr))
var = (Var *) ((ConvertRowtypeExpr *) var)->arg;
else
elog(ERROR, "unexpected node type in reltargetlist: %d",
(int) nodeTag(var));
}
if (!IsA(var, Var))
elog(ERROR, "unexpected node type in reltargetlist: %d",
(int) nodeTag(var));
/* Get the Var's original base rel */
baserel = find_base_rel(root, var->varno);
@ -506,7 +504,7 @@ build_joinrel_tlist(PlannerInfo *root, RelOptInfo *joinrel,
if (bms_nonempty_difference(baserel->attr_needed[ndx], relids))
{
/* Yup, add it to the output */
joinrel->reltargetlist = lappend(joinrel->reltargetlist, origvar);
joinrel->reltargetlist = lappend(joinrel->reltargetlist, var);
joinrel->width += baserel->attr_widths[ndx];
}
}