cost_tuplesort(Cost*startup_cost,Cost*run_cost,

doubletuples,intwidth,intcmpMultiplier,

doubletuples,intwidth,doublecmpMultiplier,

Costcomparison_cost,intsort_mem,

doublelimit_tuples)

{

{

Coststartup_cost;

Costrun_cost;

(pathkeys==NIL) ?2.0 :list_length(pathkeys)+1.0;

intn=list_length(pathkeys);

doublecmpMultiplier= (n==0) ?2.0 :n+1;

if (root!=NULL&&tuples>1&&n>1)

{

PathKey*key=linitial_node(PathKey,pathkeys);

boolisdefault;

VariableStatDatavardata;

doublend=-1;

Bitmapset*relids=pull_varnos(root, (Node*)key->source_expr);

if (!bms_is_member(0,relids))

{

examine_variable(root, (Node*)key->source_expr,0,&vardata);

if (HeapTupleIsValid(vardata.statsTuple))

{

nd=get_variable_numdistinct(&vardata,&isdefault);

if (!isdefault)

{

if (tuples >=nd)

2.0+ ((tuples-nd) / (tuples-1))* (n-1);

}

}

ReleaseVariableStats(vardata);

}

}

cost_tuplesort(&startup_cost,&run_cost,

tuples,width,cmpMultiplier,

QUERY PLAN

-------------------------------------------------------------------------------

GroupAggregate

Group Key: t1.z, t1.w, t1.x, t1.y

-> Incremental Sort

Sort Key: t1.z, t1.w, t1.x, t1.y

Presorted Key: t1.z, t1.w, t1.x

Group Key: t1.x, t1.y, t1.z, t1.w

-> Sort

Sort Key: t1.x, t1.y, t1.z, t1.w

-> Merge Join

Merge Cond: ((t1.z = t2.z) AND (t1.w = t2.w) AND (t1.x = t2.x))

Merge Cond: ((t1.w = t2.w) AND (t1.z = t2.z) AND (t1.x = t2.x))

-> Sort

Sort Key: t1.z, t1.w, t1.x

Sort Key: t1.w, t1.z, t1.x

-> Index Scan using btg_x_y_idx on btg t1

-> Sort

Sort Key: t2.z, t2.w, t2.x

Sort Key: t2.w, t2.z, t2.x

-> Index Scan using btg_x_y_idx on btg t2

(13 rows)

(12 rows)

RESET enable_nestloop;

RESET enable_hashjoin;

Sort

Sort Key: ((x * x)), z

-> GroupAggregate

Group Key: x, y, w, z

-> Incremental Sort

Sort Key: x, y, w, z

Presorted Key: x, y

Group Key: w, x, y, z

-> Sort

Sort Key: w, x, y, z

-> Index Scan using btg_x_y_idx on btg

(8 rows)

(7 rows)

-- Test the case where the number of incoming subtree path keys is more than

-- the number of grouping keys.

-> Sort

Sort Key: (COALESCE(prt1_2.a, p2_2.a)), (COALESCE(prt1_2.b, p2_2.b))

-> Merge Full Join

Merge Cond: ((prt1_2.a = p2_2.a) AND (prt1_2.b = p2_2.b))

Merge Cond: ((prt1_2.b = p2_2.b) AND (prt1_2.a = p2_2.a))

Filter: ((COALESCE(prt1_2.a, p2_2.a) >= 490) AND (COALESCE(prt1_2.a, p2_2.a) <= 510))

-> Sort

Sort Key: prt1_2.a, prt1_2.b

Sort Key: prt1_2.b, prt1_2.a

-> Seq Scan on prt1_p3 prt1_2

-> Sort

Sort Key: p2_2.a, p2_2.b

Sort Key: p2_2.b, p2_2.a

-> Seq Scan on prt2_p3 p2_2

(43 rows)