database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-27 12:41:57 +03:00
Code Activity

Teach tid-scan code to make use of "ctid = ANY (array)" clauses, so that

Browse Source 
"ctid IN (list)" will still work after we convert IN to ScalarArrayOpExpr.
Make some minor efficiency improvements while at it, such as ensuring that
multiple TIDs are fetched in physical heap order.  And fix EXPLAIN so that
it shows what's really going on for a TID scan.
This commit is contained in:
Tom Lane
2005-11-26 22:14:57 +00:00
parent a66e2c8885
commit da27c0a1ef
15 changed files with 378 additions and 147 deletions
Download Patch File Download Diff File Expand all files Collapse all files

67
src/backend/optimizer/path/costsize.c
View File

@ -49,7 +49,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.150 2005/11/22 18:17:12 momjian Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.151 2005/11/26 22:14:56 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -66,6 +66,7 @@
#include "optimizer/pathnode.h"
#include "optimizer/plancat.h"
#include "parser/parsetree.h"
#include "utils/array.h"
#include "utils/selfuncs.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"
@ -104,6 +105,7 @@ bool enable_hashjoin = true;
static bool cost_qual_eval_walker(Node *node, QualCost *total);
static int estimate_array_length(Node *arrayexpr);
static Selectivity approx_selectivity(PlannerInfo *root, List *quals,
JoinType jointype);
static Selectivity join_in_selectivity(JoinPath *path, PlannerInfo *root);
@ -617,12 +619,13 @@ cost_bitmap_or_node(BitmapOrPath *path, PlannerInfo *root)
*/
void
cost_tidscan(Path *path, PlannerInfo *root,
RelOptInfo *baserel, List *tideval)
RelOptInfo *baserel, List *tidquals)
{
Cost startup_cost = 0;
Cost run_cost = 0;
Cost cpu_per_tuple;
int ntuples = list_length(tideval);
int ntuples;
ListCell *l;
/* Should only be applied to base relations */
Assert(baserel->relid > 0);
@ -631,6 +634,25 @@ cost_tidscan(Path *path, PlannerInfo *root,
if (!enable_tidscan)
startup_cost += disable_cost;
/* Count how many tuples we expect to retrieve */
ntuples = 0;
foreach(l, tidquals)
{
if (IsA(lfirst(l), ScalarArrayOpExpr))
{
/* Each element of the array yields 1 tuple */
ScalarArrayOpExpr *saop = (ScalarArrayOpExpr *) lfirst(l);
Node *arraynode = (Node *) lsecond(saop->args);
ntuples += estimate_array_length(arraynode);
}
else
{
/* It's just CTID = something, count 1 tuple */
ntuples++;
}
}
/* disk costs --- assume each tuple on a different page */
run_cost += random_page_cost * ntuples;
@ -643,6 +665,34 @@ cost_tidscan(Path *path, PlannerInfo *root,
path->total_cost = startup_cost + run_cost;
}
/*
* Estimate number of elements in the array yielded by an expression.
*/
static int
estimate_array_length(Node *arrayexpr)
{
if (arrayexpr && IsA(arrayexpr, Const))
{
Datum arraydatum = ((Const *) arrayexpr)->constvalue;
bool arrayisnull = ((Const *) arrayexpr)->constisnull;
ArrayType *arrayval;
if (arrayisnull)
return 0;
arrayval = DatumGetArrayTypeP(arraydatum);
return ArrayGetNItems(ARR_NDIM(arrayval), ARR_DIMS(arrayval));
}
else if (arrayexpr && IsA(arrayexpr, ArrayExpr))
{
return list_length(((ArrayExpr *) arrayexpr)->elements);
}
else
{
/* default guess */
return 10;
}
}
/*
* cost_subqueryscan
* Determines and returns the cost of scanning a subquery RTE.
@ -1549,8 +1599,15 @@ cost_qual_eval_walker(Node *node, QualCost *total)
total->per_tuple += cpu_operator_cost;
else if (IsA(node, ScalarArrayOpExpr))
{
/* should charge more than 1 op cost, but how many? */
total->per_tuple += cpu_operator_cost * 10;
/*
* Estimate that the operator will be applied to about half of the
* array elements before the answer is determined.
*/
ScalarArrayOpExpr *saop = (ScalarArrayOpExpr *) node;
Node *arraynode = (Node *) lsecond(saop->args);
total->per_tuple +=
cpu_operator_cost * estimate_array_length(arraynode) * 0.5;
}
else if (IsA(node, SubLink))
{

111
src/backend/optimizer/path/tidpath.c
View File

@ -6,8 +6,10 @@
*
* What we are looking for here is WHERE conditions of the form
* "CTID = pseudoconstant", which can be implemented by just fetching
* the tuple directly via heap_fetch(). We can also handle OR conditions
* if each OR arm contains such a condition; in particular this allows
* the tuple directly via heap_fetch(). We can also handle OR'd conditions
* such as (CTID = const1) OR (CTID = const2), as well as ScalarArrayOpExpr
* conditions of the form CTID = ANY(pseudoconstant_array). In particular
* this allows
* WHERE ctid IN (tid1, tid2, ...)
*
* There is currently no special support for joins involving CTID; in
@ -22,7 +24,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/tidpath.c,v 1.25 2005/10/15 02:49:20 momjian Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/tidpath.c,v 1.26 2005/11/26 22:14:56 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -37,9 +39,10 @@
#include "parser/parse_expr.h"
static Node *IsTidEqualClause(int varno, OpExpr *node);
static List *TidQualFromExpr(int varno, Node *expr);
static List *TidQualFromRestrictinfo(int varno, List *restrictinfo);
static bool IsTidEqualClause(OpExpr *node, int varno);
static bool IsTidEqualAnyClause(ScalarArrayOpExpr *node, int varno);
static List *TidQualFromExpr(Node *expr, int varno);
static List *TidQualFromRestrictinfo(List *restrictinfo, int varno);
/*
@ -48,14 +51,12 @@ static List *TidQualFromRestrictinfo(int varno, List *restrictinfo);
* or
* pseudoconstant = CTID
*
* If it is, return the pseudoconstant subnode; if not, return NULL.
*
* We check that the CTID Var belongs to relation "varno". That is probably
* redundant considering this is only applied to restriction clauses, but
* let's be safe.
*/
static Node *
IsTidEqualClause(int varno, OpExpr *node)
static bool
IsTidEqualClause(OpExpr *node, int varno)
{
Node *arg1,
*arg2,
@ -64,9 +65,9 @@ IsTidEqualClause(int varno, OpExpr *node)
/* Operator must be tideq */
if (node->opno != TIDEqualOperator)
return NULL;
return false;
if (list_length(node->args) != 2)
return NULL;
return false;
arg1 = linitial(node->args);
arg2 = lsecond(node->args);
@ -91,20 +92,61 @@ IsTidEqualClause(int varno, OpExpr *node)
other = arg1;
}
if (!other)
return NULL;
return false;
if (exprType(other) != TIDOID)
return NULL; /* probably can't happen */
return false; /* probably can't happen */
/* The other argument must be a pseudoconstant */
if (!is_pseudo_constant_clause(other))
return NULL;
return false;
return other; /* success */
return true; /* success */
}
/*
* Check to see if a clause is of the form
* CTID = ANY (pseudoconstant_array)
*/
static bool
IsTidEqualAnyClause(ScalarArrayOpExpr *node, int varno)
{
Node *arg1,
*arg2;
/* Operator must be tideq */
if (node->opno != TIDEqualOperator)
return false;
if (!node->useOr)
return false;
Assert(list_length(node->args) == 2);
arg1 = linitial(node->args);
arg2 = lsecond(node->args);
/* CTID must be first argument */
if (arg1 && IsA(arg1, Var))
{
Var *var = (Var *) arg1;
if (var->varattno == SelfItemPointerAttributeNumber &&
var->vartype == TIDOID &&
var->varno == varno &&
var->varlevelsup == 0)
{
/* The other argument must be a pseudoconstant */
if (is_pseudo_constant_clause(arg2))
return true; /* success */
}
}
return false;
}
/*
* Extract a set of CTID conditions from the given qual expression
*
* Returns a List of CTID qual expressions (with implicit OR semantics
* across the list), or NIL if there are no usable conditions.
*
* If the expression is an AND clause, we can use a CTID condition
* from any sub-clause. If it is an OR clause, we must be able to
* extract a CTID condition from every sub-clause, or we can't use it.
@ -113,30 +155,30 @@ IsTidEqualClause(int varno, OpExpr *node)
* sub-clauses, in which case we could try to pick the most efficient one.
* In practice, such usage seems very unlikely, so we don't bother; we
* just exit as soon as we find the first candidate.
*
* Returns a List of pseudoconstant TID expressions, or NIL if no match.
* (Has to be a list for the OR case.)
*/
static List *
TidQualFromExpr(int varno, Node *expr)
TidQualFromExpr(Node *expr, int varno)
{
List *rlst = NIL,
*frtn;
List *rlst = NIL;
ListCell *l;
Node *rnode;
if (is_opclause(expr))
{
/* base case: check for tideq opclause */
rnode = IsTidEqualClause(varno, (OpExpr *) expr);
if (rnode)
rlst = list_make1(rnode);
if (IsTidEqualClause((OpExpr *) expr, varno))
rlst = list_make1(expr);
}
else if (expr && IsA(expr, ScalarArrayOpExpr))
{
/* another base case: check for tid = ANY clause */
if (IsTidEqualAnyClause((ScalarArrayOpExpr *) expr, varno))
rlst = list_make1(expr);
}
else if (and_clause(expr))
{
foreach(l, ((BoolExpr *) expr)->args)
{
rlst = TidQualFromExpr(varno, (Node *) lfirst(l));
rlst = TidQualFromExpr((Node *) lfirst(l), varno);
if (rlst)
break;
}
@ -145,7 +187,8 @@ TidQualFromExpr(int varno, Node *expr)
{
foreach(l, ((BoolExpr *) expr)->args)
{
frtn = TidQualFromExpr(varno, (Node *) lfirst(l));
List *frtn = TidQualFromExpr((Node *) lfirst(l), varno);
if (frtn)
rlst = list_concat(rlst, frtn);
else
@ -167,7 +210,7 @@ TidQualFromExpr(int varno, Node *expr)
* except for the format of the input.
*/
static List *
TidQualFromRestrictinfo(int varno, List *restrictinfo)
TidQualFromRestrictinfo(List *restrictinfo, int varno)
{
List *rlst = NIL;
ListCell *l;
@ -178,7 +221,7 @@ TidQualFromRestrictinfo(int varno, List *restrictinfo)
if (!IsA(rinfo, RestrictInfo))
continue; /* probably should never happen */
rlst = TidQualFromExpr(varno, (Node *) rinfo->clause);
rlst = TidQualFromExpr((Node *) rinfo->clause, varno);
if (rlst)
break;
}
@ -194,10 +237,10 @@ TidQualFromRestrictinfo(int varno, List *restrictinfo)
void
create_tidscan_paths(PlannerInfo *root, RelOptInfo *rel)
{
List *tideval;
List *tidquals;
tideval = TidQualFromRestrictinfo(rel->relid, rel->baserestrictinfo);
tidquals = TidQualFromRestrictinfo(rel->baserestrictinfo, rel->relid);
if (tideval)
add_path(rel, (Path *) create_tidscan_path(root, rel, tideval));
if (tidquals)
add_path(rel, (Path *) create_tidscan_path(root, rel, tidquals));
}