I wrote:
> Heikki Linnakangas <[email protected]> writes:
>> But do we really need to backpatch any of this?
> Alexey's example consumes only a couple hundred MB in 9.2, vs about 7GB
> peak in 9.3 and up. That seems like a pretty nasty regression.
I did a bit more measurement of the time and backend memory consumption
for Alexey's example EXPLAIN:
9.2: 0.9 sec, circa 200 MB
HEAD: 56 sec, circa 7300 MB
with patch below: 3.7 sec, circa 300 MB
So while this doesn't get us all the way back down to where we were before
we started trying to guarantee unique table/column identifiers in EXPLAIN
printouts, it's at least a lot closer.
Not sure whether to just commit this to HEAD and call it a day, or to
risk back-patching.
It occurred to me that we could use your idea of a secondary data
structure and minimize the code impact with a macro layer, ie
#define grouping_stack pointer_field->groupingstack
But I'm not sure if it's worth the trouble. 9.3 has been like this
right along, and this is the first complaint.
One compromise idea would be to back-patch only as far as 9.4.
If there are extensions out there that have this ABI issue, expecting
them to rebuild for 9.4.1 might be OK.
regards, tom lane
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 8a0be5d..39ceaf2 100644
*** a/src/backend/commands/explain.c
--- b/src/backend/commands/explain.c
*************** ExplainPrintPlan(ExplainState *es, Query
*** 563,568 ****
--- 563,570 ----
es->rtable = queryDesc->plannedstmt->rtable;
ExplainPreScanNode(queryDesc->planstate, &rels_used);
es->rtable_names = select_rtable_names_for_explain(es->rtable, rels_used);
+ es->deparse_cxt = deparse_context_for_plan_rtable(es->rtable,
+ es->rtable_names);
ExplainNode(queryDesc->planstate, NIL, NULL, NULL, es);
}
*************** show_plan_tlist(PlanState *planstate, Li
*** 1678,1687 ****
return;
/* Set up deparsing context */
! context = deparse_context_for_planstate((Node *) planstate,
! ancestors,
! es->rtable,
! es->rtable_names);
useprefix = list_length(es->rtable) > 1;
/* Deparse each result column (we now include resjunk ones) */
--- 1680,1688 ----
return;
/* Set up deparsing context */
! context = set_deparse_context_planstate(es->deparse_cxt,
! (Node *) planstate,
! ancestors);
useprefix = list_length(es->rtable) > 1;
/* Deparse each result column (we now include resjunk ones) */
*************** show_expression(Node *node, const char *
*** 1710,1719 ****
char *exprstr;
/* Set up deparsing context */
! context = deparse_context_for_planstate((Node *) planstate,
! ancestors,
! es->rtable,
! es->rtable_names);
/* Deparse the expression */
exprstr = deparse_expression(node, context, useprefix, false);
--- 1711,1719 ----
char *exprstr;
/* Set up deparsing context */
! context = set_deparse_context_planstate(es->deparse_cxt,
! (Node *) planstate,
! ancestors);
/* Deparse the expression */
exprstr = deparse_expression(node, context, useprefix, false);
*************** show_sort_group_keys(PlanState *planstat
*** 1855,1864 ****
return;
/* Set up deparsing context */
! context = deparse_context_for_planstate((Node *) planstate,
! ancestors,
! es->rtable,
! es->rtable_names);
useprefix = (list_length(es->rtable) > 1 || es->verbose);
for (keyno = 0; keyno < nkeys; keyno++)
--- 1855,1863 ----
return;
/* Set up deparsing context */
! context = set_deparse_context_planstate(es->deparse_cxt,
! (Node *) planstate,
! ancestors);
useprefix = (list_length(es->rtable) > 1 || es->verbose);
for (keyno = 0; keyno < nkeys; keyno++)
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index dd748ac..cacd72c 100644
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
*************** deparse_context_for(const char *aliasnam
*** 2520,2526 ****
}
/*
! * deparse_context_for_planstate - Build deparse context for a plan
*
* When deparsing an expression in a Plan tree, we might have to resolve
* OUTER_VAR, INNER_VAR, or INDEX_VAR references. To do this, the caller must
--- 2520,2562 ----
}
/*
! * deparse_context_for_plan_rtable - Build deparse context for a plan's rtable
! *
! * When deparsing an expression in a Plan tree, we use the plan's rangetable
! * to resolve names of simple Vars. The initialization of column names for
! * this is rather expensive if the rangetable is large, and it'll be the same
! * for every expression in the Plan tree; so we do it just once and re-use
! * the result of this function for each expression. (Note that the result
! * is not usable until set_deparse_context_planstate() is applied to it.)
! *
! * In addition to the plan's rangetable list, pass the per-RTE alias names
! * assigned by a previous call to select_rtable_names_for_explain.
! */
! List *
! deparse_context_for_plan_rtable(List *rtable, List *rtable_names)
! {
! deparse_namespace *dpns;
!
! dpns = (deparse_namespace *) palloc0(sizeof(deparse_namespace));
!
! /* Initialize fields that stay the same across the whole plan tree */
! dpns->rtable = rtable;
! dpns->rtable_names = rtable_names;
! dpns->ctes = NIL;
!
! /*
! * Set up column name aliases. We will get rather bogus results for join
! * RTEs, but that doesn't matter because plan trees don't contain any join
! * alias Vars.
! */
! set_simple_column_names(dpns);
!
! /* Return a one-deep namespace stack */
! return list_make1(dpns);
! }
!
! /*
! * set_deparse_context_planstate - Specify Plan node containing expression
*
* When deparsing an expression in a Plan tree, we might have to resolve
* OUTER_VAR, INNER_VAR, or INDEX_VAR references. To do this, the caller must
*************** deparse_context_for(const char *aliasnam
*** 2539,2575 ****
* most-closely-nested first. This is needed to resolve PARAM_EXEC Params.
* Note we assume that all the PlanStates share the same rtable.
*
! * The plan's rangetable list must also be passed, along with the per-RTE
! * alias names assigned by a previous call to select_rtable_names_for_explain.
! * (We use the rangetable to resolve simple Vars, but the plan inputs are
! * necessary for Vars with special varnos.)
*/
List *
! deparse_context_for_planstate(Node *planstate, List *ancestors,
! List *rtable, List *rtable_names)
{
deparse_namespace *dpns;
! dpns = (deparse_namespace *) palloc0(sizeof(deparse_namespace));
!
! /* Initialize fields that stay the same across the whole plan tree */
! dpns->rtable = rtable;
! dpns->rtable_names = rtable_names;
! dpns->ctes = NIL;
!
! /*
! * Set up column name aliases. We will get rather bogus results for join
! * RTEs, but that doesn't matter because plan trees don't contain any join
! * alias Vars.
! */
! set_simple_column_names(dpns);
/* Set our attention on the specific plan node passed in */
set_deparse_planstate(dpns, (PlanState *) planstate);
dpns->ancestors = ancestors;
! /* Return a one-deep namespace stack */
! return list_make1(dpns);
}
/*
--- 2575,2602 ----
* most-closely-nested first. This is needed to resolve PARAM_EXEC Params.
* Note we assume that all the PlanStates share the same rtable.
*
! * Once this function has been called, deparse_expression() can be called on
! * subsidiary expression(s) of the specified PlanState node. To deparse
! * expressions of a different Plan node in the same Plan tree, re-call this
! * function to identify the new parent Plan node.
! *
! * The result is the same List passed in; this is a notational convenience.
*/
List *
! set_deparse_context_planstate(List *dpcontext,
! Node *planstate, List *ancestors)
{
deparse_namespace *dpns;
! /* Should always have one-entry namespace list for Plan deparsing */
! Assert(list_length(dpcontext) == 1);
! dpns = (deparse_namespace *) linitial(dpcontext);
/* Set our attention on the specific plan node passed in */
set_deparse_planstate(dpns, (PlanState *) planstate);
dpns->ancestors = ancestors;
! return dpcontext;
}
/*
diff --git a/src/include/commands/explain.h b/src/include/commands/explain.h
index 6e26950..598f374 100644
*** a/src/include/commands/explain.h
--- b/src/include/commands/explain.h
*************** typedef struct ExplainState
*** 41,46 ****
--- 41,47 ----
List *rtable_names; /* alias names for RTEs */
int indent; /* current indentation level */
List *grouping_stack; /* format-specific grouping state */
+ List *deparse_cxt; /* context list for deparsing expressions */
} ExplainState;
/* Hook for plugins to get control in ExplainOneQuery() */
diff --git a/src/include/utils/ruleutils.h b/src/include/utils/ruleutils.h
index 188503c..86d2bea 100644
*** a/src/include/utils/ruleutils.h
--- b/src/include/utils/ruleutils.h
*************** extern char *pg_get_constraintdef_string
*** 25,32 ****
extern char *deparse_expression(Node *expr, List *dpcontext,
bool forceprefix, bool showimplicit);
extern List *deparse_context_for(const char *aliasname, Oid relid);
! extern List *deparse_context_for_planstate(Node *planstate, List *ancestors,
! List *rtable, List *rtable_names);
extern List *select_rtable_names_for_explain(List *rtable,
Bitmapset *rels_used);
extern char *generate_collation_name(Oid collid);
--- 25,33 ----
extern char *deparse_expression(Node *expr, List *dpcontext,
bool forceprefix, bool showimplicit);
extern List *deparse_context_for(const char *aliasname, Oid relid);
! extern List *deparse_context_for_plan_rtable(List *rtable, List *rtable_names);
! extern List *set_deparse_context_planstate(List *dpcontext,
! Node *planstate, List *ancestors);
extern List *select_rtable_names_for_explain(List *rtable,
Bitmapset *rels_used);
extern char *generate_collation_name(Oid collid);
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