On Fri, Mar 1, 2019 at 4:33 AM Kyotaro HORIGUCHI <
[email protected]> wrote:
> Hello.
>
> At Thu, 28 Feb 2019 21:16:25 +0100, Tomas Vondra <
> [email protected]> wrote in <
> [email protected]>
> > > One biggest issue seems to be we don't know the total number of
>
> # One *of* the biggest *issues*?
>
> > > outer tuples before actually reading a null tuple. I doubt of
> > > general shortcut for that. It also seems preventing limit node
> > > from just using materialized outer.
> > >
> >
> > Sure, if you actually want all tuples, you'll have to execute the outer
> > plan till completion. But that's not what I'm talking about - what if we
> > only ever need to read one row from the limit?
>
> We have no choice than once reading all tuples just to find we
> are to return just one row, since estimator is not guaranteed to
> be exact as required for this purpose.
>
> > To give you a (admittedly, somewhat contrived and artificial example):
> >
> > SELECT * FROM t1 WHERE id IN (
> > SELECT id FROM t2 ORDER BY x FETCH FIRST 10 PERCENT ROWS ONLY
> > );
> >
> > Maybe this example is bogus and/or does not really matter in practice. I
> > don't know, but I've been unable to convince myself that's the case.
>
> I see such kind of idiom common. Even in the quite simple example
> above, *we* cannot tell how many tuples the inner should return
> unless we actually fetch all tuples in t2. This is the same
> problem with count(*).
>
> The query is equivalent to the folloing one.
>
> SELECT * FROM t1 WHERE id IN (
> SELECT id FROM t2 ORDER BY x
> FETCH FIRST (SELECT ceil(count(*) * 0.1) FROM t2) ROWS ONLY
> );
>
> This scans t2 twice, but this patch does only one full scan
> moving another partial scan to tuplestore. We would win if the
> outer is complex enough.
>
Okay here is the previous implementation with uptread review comment
included and it also consider OFFSET clause in percentage calculation
regards
Surafel
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 06d611b64c..e3ce4d7e36 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -44,7 +44,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
[ ORDER BY <replaceable class="parameter">expression</replaceable> [ ASC | DESC | USING <replaceable class="parameter">operator</replaceable> ] [ NULLS { FIRST | LAST } ] [, ...] ]
[ LIMIT { <replaceable class="parameter">count</replaceable> | ALL } ]
[ OFFSET <replaceable class="parameter">start</replaceable> [ ROW | ROWS ] ]
- [ FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] { ROW | ROWS } ONLY ]
+ [ FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] [ PERCENT ] { ROW | ROWS } ONLY ]
[ FOR { UPDATE | NO KEY UPDATE | SHARE | KEY SHARE } [ OF <replaceable class="parameter">table_name</replaceable> [, ...] ] [ NOWAIT | SKIP LOCKED ] [...] ]
<phrase>where <replaceable class="parameter">from_item</replaceable> can be one of:</phrase>
@@ -1430,7 +1430,7 @@ OFFSET <replaceable class="parameter">start</replaceable>
which <productname>PostgreSQL</productname> also supports. It is:
<synopsis>
OFFSET <replaceable class="parameter">start</replaceable> { ROW | ROWS }
-FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] { ROW | ROWS } ONLY
+FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] [ PERCENT ] { ROW | ROWS } ONLY
</synopsis>
In this syntax, the <replaceable class="parameter">start</replaceable>
or <replaceable class="parameter">count</replaceable> value is required by
@@ -1440,7 +1440,8 @@ FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] {
ambiguity.
If <replaceable class="parameter">count</replaceable> is
omitted in a <literal>FETCH</literal> clause, it defaults to 1.
- <literal>ROW</literal>
+ with <literal>PERCENT</literal> count specifies the maximum number of rows to return
+ in percentage.<literal>ROW</literal>
and <literal>ROWS</literal> as well as <literal>FIRST</literal>
and <literal>NEXT</literal> are noise words that don't influence
the effects of these clauses.
diff --git a/src/backend/executor/nodeLimit.c b/src/backend/executor/nodeLimit.c
index baa669abe8..2be6f655fb 100644
--- a/src/backend/executor/nodeLimit.c
+++ b/src/backend/executor/nodeLimit.c
@@ -43,6 +43,7 @@ ExecLimit(PlanState *pstate)
LimitState *node = castNode(LimitState, pstate);
ScanDirection direction;
TupleTableSlot *slot;
+ TupleDesc tupleDescriptor;
PlanState *outerPlan;
CHECK_FOR_INTERRUPTS();
@@ -52,6 +53,8 @@ ExecLimit(PlanState *pstate)
*/
direction = node->ps.state->es_direction;
outerPlan = outerPlanState(node);
+ slot = node->subSlot;
+ tupleDescriptor = node->ps.ps_ResultTupleDesc;
/*
* The main logic is a simple state machine.
@@ -60,6 +63,26 @@ ExecLimit(PlanState *pstate)
{
case LIMIT_INITIAL:
+ if (node->limitOption == PERCENTAGE)
+ {
+
+ /*
+ * In PERCENTAGE option the number of tuple to return can't
+ * be determine before receiving the last tuple. so execute
+ * outerPlan until the end and store the result tuple to avoid
+ * executing twice
+ */
+ for (;;)
+ {
+ slot = ExecProcNode(outerPlan);
+ if (TupIsNull(slot))
+ {
+ break;
+ }
+ tuplestore_puttupleslot(node->tuple_store, slot);
+ }
+ }
+
/*
* First call for this node, so compute limit/offset. (We can't do
* this any earlier, because parameters from upper nodes will not
@@ -87,24 +110,47 @@ ExecLimit(PlanState *pstate)
return NULL;
}
- /*
- * Fetch rows from subplan until we reach position > offset.
- */
- for (;;)
+ if (node->limitOption == PERCENTAGE)
{
- slot = ExecProcNode(outerPlan);
- if (TupIsNull(slot))
+ /* In PERCENTAGE case the result is already in tuplestore */
+ for (;;)
{
- /*
- * The subplan returns too few tuples for us to produce
- * any output at all.
- */
- node->lstate = LIMIT_EMPTY;
- return NULL;
+ slot = MakeSingleTupleTableSlot(tupleDescriptor, &TTSOpsMinimalTuple);
+ if (!tuplestore_gettupleslot(node->tuple_store, true, true, slot))
+ {
+ node->lstate = LIMIT_EMPTY;
+ return NULL;
+ }
+ else
+ {
+ node->subSlot = slot;
+ if (++node->position > node->offset)
+ break;
+ }
+ }
+ }
+ else if (node->limitOption == EXACT_NUMBER)
+ {
+
+ /*
+ * Fetch rows from subplan until we reach position > offset.
+ */
+ for (;;)
+ {
+ slot = ExecProcNode(outerPlan);
+ if (TupIsNull(slot))
+ {
+ /*
+ * The subplan returns too few tuples for us to produce
+ * any output at all.
+ */
+ node->lstate = LIMIT_EMPTY;
+ return NULL;
+ }
+ node->subSlot = slot;
+ if (++node->position > node->offset)
+ break;
}
- node->subSlot = slot;
- if (++node->position > node->offset)
- break;
}
/*
@@ -145,17 +191,36 @@ ExecLimit(PlanState *pstate)
return NULL;
}
- /*
- * Get next tuple from subplan, if any.
- */
- slot = ExecProcNode(outerPlan);
- if (TupIsNull(slot))
+ /* In PERCENTAGE case the result is already in tuplestore */
+ if (node->limitOption == PERCENTAGE)
{
- node->lstate = LIMIT_SUBPLANEOF;
- return NULL;
+ slot = MakeSingleTupleTableSlot(tupleDescriptor, &TTSOpsMinimalTuple);
+ if (tuplestore_gettupleslot(node->tuple_store, true, false, slot))
+ {
+ node->subSlot = slot;
+ node->position++;
+ }
+ else
+ {
+ node->lstate = LIMIT_SUBPLANEOF;
+ return NULL;
+ }
+ }
+ else if (node->limitOption == EXACT_NUMBER)
+ {
+
+ /*
+ * Get next tuple from subplan, if any.
+ */
+ slot = ExecProcNode(outerPlan);
+ if (TupIsNull(slot))
+ {
+ node->lstate = LIMIT_SUBPLANEOF;
+ return NULL;
+ }
+ node->subSlot = slot;
+ node->position++;
}
- node->subSlot = slot;
- node->position++;
}
else
{
@@ -169,14 +234,30 @@ ExecLimit(PlanState *pstate)
return NULL;
}
- /*
- * Get previous tuple from subplan; there should be one!
- */
- slot = ExecProcNode(outerPlan);
- if (TupIsNull(slot))
- elog(ERROR, "LIMIT subplan failed to run backwards");
- node->subSlot = slot;
- node->position--;
+ /* In PERCENTAGE case the result is already in tuplestore */
+ if (node->limitOption == PERCENTAGE)
+ {
+ if (tuplestore_gettupleslot(node->tuple_store, false, false, slot))
+ {
+ node->subSlot = slot;
+ node->position--;
+ }
+ else
+ elog(ERROR, "LIMIT subplan failed to run backwards");
+
+ }
+ else if (node->limitOption == EXACT_NUMBER)
+ {
+
+ /*
+ * Get previous tuple from subplan; there should be one!
+ */
+ slot = ExecProcNode(outerPlan);
+ if (TupIsNull(slot))
+ elog(ERROR, "LIMIT subplan failed to run backwards");
+ node->subSlot = slot;
+ node->position--;
+ }
}
break;
@@ -184,15 +265,30 @@ ExecLimit(PlanState *pstate)
if (ScanDirectionIsForward(direction))
return NULL;
- /*
- * Backing up from subplan EOF, so re-fetch previous tuple; there
- * should be one! Note previous tuple must be in window.
- */
- slot = ExecProcNode(outerPlan);
- if (TupIsNull(slot))
- elog(ERROR, "LIMIT subplan failed to run backwards");
- node->subSlot = slot;
- node->lstate = LIMIT_INWINDOW;
+ /* In PERCENTAGE case the result is already in tuplestore */
+ if (node->limitOption == PERCENTAGE)
+ {
+ if (tuplestore_gettupleslot(node->tuple_store, true, false, slot))
+ {
+ node->subSlot = slot;
+ node->lstate = LIMIT_INWINDOW;
+ }
+ else
+ elog(ERROR, "LIMIT subplan failed to run backwards");
+ }
+ else if (node->limitOption == EXACT_NUMBER)
+ {
+
+ /*
+ * Backing up from subplan EOF, so re-fetch previous tuple; there
+ * should be one! Note previous tuple must be in window.
+ */
+ slot = ExecProcNode(outerPlan);
+ if (TupIsNull(slot))
+ elog(ERROR, "LIMIT subplan failed to run backwards");
+ node->subSlot = slot;
+ node->lstate = LIMIT_INWINDOW;
+ }
/* position does not change 'cause we didn't advance it before */
break;
@@ -283,11 +379,16 @@ recompute_limits(LimitState *node)
}
else
{
- node->count = DatumGetInt64(val);
- if (node->count < 0)
- ereport(ERROR,
- (errcode(ERRCODE_INVALID_ROW_COUNT_IN_LIMIT_CLAUSE),
- errmsg("LIMIT must not be negative")));
+ if (node->limitOption == PERCENTAGE)
+ node->count = DatumGetFloat8(val) * tuplestore_tuple_count(node->tuple_store) / 100;
+ else
+ {
+ node->count = DatumGetInt64(val);
+ if (node->count < 0)
+ ereport(ERROR,
+ (errcode(ERRCODE_INVALID_ROW_COUNT_IN_LIMIT_CLAUSE),
+ errmsg("LIMIT must not be negative")));
+ }
node->noCount = false;
}
}
@@ -311,7 +412,8 @@ recompute_limits(LimitState *node)
* must update the child node anyway, in case this is a rescan and the
* previous time we got a different result.
*/
- ExecSetTupleBound(compute_tuples_needed(node), outerPlanState(node));
+ if (node->limitOption != PERCENTAGE)
+ ExecSetTupleBound(compute_tuples_needed(node), outerPlanState(node));
}
/*
@@ -374,6 +476,10 @@ ExecInitLimit(Limit *node, EState *estate, int eflags)
(PlanState *) limitstate);
limitstate->limitCount = ExecInitExpr((Expr *) node->limitCount,
(PlanState *) limitstate);
+ limitstate->limitOption = node->limitOption;
+
+ if (node->limitOption == PERCENTAGE)
+ limitstate->tuple_store= tuplestore_begin_heap(true, false, work_mem);
/*
* Initialize result type.
@@ -405,6 +511,8 @@ ExecEndLimit(LimitState *node)
{
ExecFreeExprContext(&node->ps);
ExecEndNode(outerPlanState(node));
+ if (node->tuple_store!= NULL)
+ tuplestore_end(node->tuple_store);
}
@@ -424,4 +532,6 @@ ExecReScanLimit(LimitState *node)
*/
if (node->ps.lefttree->chgParam == NULL)
ExecReScan(node->ps.lefttree);
+ if (node->tuple_store!= NULL)
+ tuplestore_rescan(node->tuple_store);
}
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index e15724bb0e..dc0fe7b693 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -1136,6 +1136,7 @@ _copyLimit(const Limit *from)
*/
COPY_NODE_FIELD(limitOffset);
COPY_NODE_FIELD(limitCount);
+ COPY_SCALAR_FIELD(limitOption);
return newnode;
}
@@ -3022,6 +3023,7 @@ _copyQuery(const Query *from)
COPY_NODE_FIELD(sortClause);
COPY_NODE_FIELD(limitOffset);
COPY_NODE_FIELD(limitCount);
+ COPY_SCALAR_FIELD(limitOption);
COPY_NODE_FIELD(rowMarks);
COPY_NODE_FIELD(setOperations);
COPY_NODE_FIELD(constraintDeps);
@@ -3106,6 +3108,7 @@ _copySelectStmt(const SelectStmt *from)
COPY_NODE_FIELD(sortClause);
COPY_NODE_FIELD(limitOffset);
COPY_NODE_FIELD(limitCount);
+ COPY_SCALAR_FIELD(limitOption);
COPY_NODE_FIELD(lockingClause);
COPY_NODE_FIELD(withClause);
COPY_SCALAR_FIELD(op);
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 31499eb798..146984cd44 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -974,6 +974,7 @@ _equalQuery(const Query *a, const Query *b)
COMPARE_NODE_FIELD(sortClause);
COMPARE_NODE_FIELD(limitOffset);
COMPARE_NODE_FIELD(limitCount);
+ COMPARE_SCALAR_FIELD(limitOption);
COMPARE_NODE_FIELD(rowMarks);
COMPARE_NODE_FIELD(setOperations);
COMPARE_NODE_FIELD(constraintDeps);
@@ -1048,6 +1049,7 @@ _equalSelectStmt(const SelectStmt *a, const SelectStmt *b)
COMPARE_NODE_FIELD(sortClause);
COMPARE_NODE_FIELD(limitOffset);
COMPARE_NODE_FIELD(limitCount);
+ COMPARE_SCALAR_FIELD(limitOption);
COMPARE_NODE_FIELD(lockingClause);
COMPARE_NODE_FIELD(withClause);
COMPARE_SCALAR_FIELD(op);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 65302fe65b..62fc11582d 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -900,6 +900,7 @@ _outLimit(StringInfo str, const Limit *node)
WRITE_NODE_FIELD(limitOffset);
WRITE_NODE_FIELD(limitCount);
+ WRITE_ENUM_FIELD(limitOption, LimitOption);
}
static void
@@ -2097,6 +2098,7 @@ _outLimitPath(StringInfo str, const LimitPath *node)
WRITE_NODE_FIELD(subpath);
WRITE_NODE_FIELD(limitOffset);
WRITE_NODE_FIELD(limitCount);
+ WRITE_ENUM_FIELD(limitOption, LimitOption);
}
static void
@@ -2689,6 +2691,7 @@ _outSelectStmt(StringInfo str, const SelectStmt *node)
WRITE_NODE_FIELD(sortClause);
WRITE_NODE_FIELD(limitOffset);
WRITE_NODE_FIELD(limitCount);
+ WRITE_ENUM_FIELD(limitOption, LimitOption);
WRITE_NODE_FIELD(lockingClause);
WRITE_NODE_FIELD(withClause);
WRITE_ENUM_FIELD(op, SetOperation);
@@ -2898,6 +2901,7 @@ _outQuery(StringInfo str, const Query *node)
WRITE_NODE_FIELD(sortClause);
WRITE_NODE_FIELD(limitOffset);
WRITE_NODE_FIELD(limitCount);
+ WRITE_ENUM_FIELD(limitOption, LimitOption);
WRITE_NODE_FIELD(rowMarks);
WRITE_NODE_FIELD(setOperations);
WRITE_NODE_FIELD(constraintDeps);
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 5aa42242a9..f93f543dc9 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -278,6 +278,7 @@ _readQuery(void)
READ_NODE_FIELD(sortClause);
READ_NODE_FIELD(limitOffset);
READ_NODE_FIELD(limitCount);
+ READ_ENUM_FIELD(limitOption, LimitOption);
READ_NODE_FIELD(rowMarks);
READ_NODE_FIELD(setOperations);
READ_NODE_FIELD(constraintDeps);
@@ -2324,6 +2325,7 @@ _readLimit(void)
READ_NODE_FIELD(limitOffset);
READ_NODE_FIELD(limitCount);
+ READ_ENUM_FIELD(limitOption, LimitOption);
READ_DONE();
}
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 236f506cfb..a2fc9f25f6 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -2190,7 +2190,8 @@ create_minmaxagg_plan(PlannerInfo *root, MinMaxAggPath *best_path)
plan = (Plan *) make_limit(plan,
subparse->limitOffset,
- subparse->limitCount);
+ subparse->limitCount,
+ subparse->limitOption);
/* Must apply correct cost/width data to Limit node */
plan->startup_cost = mminfo->path->startup_cost;
@@ -2495,7 +2496,8 @@ create_limit_plan(PlannerInfo *root, LimitPath *best_path, int flags)
plan = make_limit(subplan,
best_path->limitOffset,
- best_path->limitCount);
+ best_path->limitCount,
+ best_path->limitOption);
copy_generic_path_info(&plan->plan, (Path *) best_path);
@@ -6359,7 +6361,7 @@ make_lockrows(Plan *lefttree, List *rowMarks, int epqParam)
* Build a Limit plan node
*/
Limit *
-make_limit(Plan *lefttree, Node *limitOffset, Node *limitCount)
+make_limit(Plan *lefttree, Node *limitOffset, Node *limitCount, LimitOption limitOption)
{
Limit *node = makeNode(Limit);
Plan *plan = &node->plan;
@@ -6371,6 +6373,7 @@ make_limit(Plan *lefttree, Node *limitOffset, Node *limitCount)
node->limitOffset = limitOffset;
node->limitCount = limitCount;
+ node->limitOption = limitOption;
return node;
}
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index bc81535905..c5a4ae7008 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -2122,12 +2122,22 @@ grouping_planner(PlannerInfo *root, bool inheritance_update,
*/
if (parse->sortClause)
{
- current_rel = create_ordered_paths(root,
- current_rel,
- final_target,
- final_target_parallel_safe,
- have_postponed_srfs ? -1.0 :
- limit_tuples);
+
+ /* In PERCENTAGE option there are no bound on the number of output tuples */
+ if (parse->limitOption == PERCENTAGE)
+ current_rel = create_ordered_paths(root,
+ current_rel,
+ final_target,
+ final_target_parallel_safe,
+ have_postponed_srfs ? -1.0 :
+ -1.0);
+ else
+ current_rel = create_ordered_paths(root,
+ current_rel,
+ final_target,
+ final_target_parallel_safe,
+ have_postponed_srfs ? -1.0 :
+ limit_tuples);
/* Fix things up if final_target contains SRFs */
if (parse->hasTargetSRFs)
adjust_paths_for_srfs(root, current_rel,
@@ -2190,6 +2200,7 @@ grouping_planner(PlannerInfo *root, bool inheritance_update,
path = (Path *) create_limit_path(root, final_rel, path,
parse->limitOffset,
parse->limitCount,
+ parse->limitOption,
offset_est, count_est);
}
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 169e51e792..69b6e4f072 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -3526,6 +3526,7 @@ LimitPath *
create_limit_path(PlannerInfo *root, RelOptInfo *rel,
Path *subpath,
Node *limitOffset, Node *limitCount,
+ LimitOption limitOption,
int64 offset_est, int64 count_est)
{
LimitPath *pathnode = makeNode(LimitPath);
@@ -3547,6 +3548,7 @@ create_limit_path(PlannerInfo *root, RelOptInfo *rel,
pathnode->subpath = subpath;
pathnode->limitOffset = limitOffset;
pathnode->limitCount = limitCount;
+ pathnode->limitOption = limitOption;
/*
* Adjust the output rows count and costs according to the offset/limit.
@@ -3588,9 +3590,21 @@ create_limit_path(PlannerInfo *root, RelOptInfo *rel,
count_rows = (double) count_est;
else
count_rows = clamp_row_est(subpath->rows * 0.10);
+ if (limitOption == PERCENTAGE)
+ {
+ double per_count = DatumGetFloat8(count_est);
+ count_rows = clamp_row_est((subpath->rows * per_count) / 100);
+ if (subpath->rows > 0)
+ {
+ pathnode->path.startup_cost = (count_rows *
+ subpath->total_cost) / subpath->rows;
+ pathnode->path.total_cost = subpath->total_cost +
+ (count_rows * 0.1);
+ }
+ }
if (count_rows > pathnode->path.rows)
count_rows = pathnode->path.rows;
- if (subpath->rows > 0)
+ if (subpath->rows > 0 && limitOption == EXACT_NUMBER)
pathnode->path.total_cost = pathnode->path.startup_cost +
(subpath->total_cost - subpath->startup_cost)
* count_rows / subpath->rows;
diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c
index e3544efb6f..3894fbd02b 100644
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -1301,10 +1301,11 @@ transformSelectStmt(ParseState *pstate, SelectStmt *stmt)
}
/* transform LIMIT */
- qry->limitOffset = transformLimitClause(pstate, stmt->limitOffset,
+ qry->limitOffset = transformLimitClause(pstate, stmt->limitOffset, stmt->limitOption,
EXPR_KIND_OFFSET, "OFFSET");
- qry->limitCount = transformLimitClause(pstate, stmt->limitCount,
+ qry->limitCount = transformLimitClause(pstate, stmt->limitCount, stmt->limitOption,
EXPR_KIND_LIMIT, "LIMIT");
+ qry->limitOption = stmt->limitOption;
/* transform window clauses after we have seen all window functions */
qry->windowClause = transformWindowDefinitions(pstate,
@@ -1549,10 +1550,11 @@ transformValuesClause(ParseState *pstate, SelectStmt *stmt)
EXPR_KIND_ORDER_BY,
false /* allow SQL92 rules */ );
- qry->limitOffset = transformLimitClause(pstate, stmt->limitOffset,
+ qry->limitOffset = transformLimitClause(pstate, stmt->limitOffset, stmt->limitOption,
EXPR_KIND_OFFSET, "OFFSET");
- qry->limitCount = transformLimitClause(pstate, stmt->limitCount,
+ qry->limitCount = transformLimitClause(pstate, stmt->limitCount, stmt->limitOption,
EXPR_KIND_LIMIT, "LIMIT");
+ qry->limitOption = stmt->limitOption;
if (stmt->lockingClause)
ereport(ERROR,
@@ -1784,10 +1786,11 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
parser_errposition(pstate,
exprLocation(list_nth(qry->targetList, tllen)))));
- qry->limitOffset = transformLimitClause(pstate, limitOffset,
+ qry->limitOffset = transformLimitClause(pstate, limitOffset, stmt->limitOption,
EXPR_KIND_OFFSET, "OFFSET");
- qry->limitCount = transformLimitClause(pstate, limitCount,
+ qry->limitCount = transformLimitClause(pstate, limitCount, stmt->limitOption,
EXPR_KIND_LIMIT, "LIMIT");
+ qry->limitOption = stmt->limitOption;
qry->rtable = pstate->p_rtable;
qry->jointree = makeFromExpr(pstate->p_joinlist, NULL);
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 0279013120..80e5aafe91 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -164,6 +164,7 @@ static List *makeOrderedSetArgs(List *directargs, List *orderedargs,
static void insertSelectOptions(SelectStmt *stmt,
List *sortClause, List *lockingClause,
Node *limitOffset, Node *limitCount,
+ void *limitOption,
WithClause *withClause,
core_yyscan_t yyscanner);
static Node *makeSetOp(SetOperation op, bool all, Node *larg, Node *rarg);
@@ -387,7 +388,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
target_list opt_target_list insert_column_list set_target_list
set_clause_list set_clause
def_list operator_def_list indirection opt_indirection
- reloption_list group_clause TriggerFuncArgs select_limit
+ reloption_list group_clause TriggerFuncArgs select_limit limit_clause
opt_select_limit opclass_item_list opclass_drop_list
opclass_purpose opt_opfamily transaction_mode_list_or_empty
OptTableFuncElementList TableFuncElementList opt_type_modifiers
@@ -449,7 +450,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
comment_type_any_name comment_type_name
security_label_type_any_name security_label_type_name
-%type <node> fetch_args limit_clause select_limit_value
+%type <node> fetch_args select_limit_value
offset_clause select_offset_value
select_fetch_first_value I_or_F_const
%type <ival> row_or_rows first_or_next
@@ -661,7 +662,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
ORDER ORDINALITY OTHERS OUT_P OUTER_P
OVER OVERLAPS OVERLAY OVERRIDING OWNED OWNER
- PARALLEL PARSER PARTIAL PARTITION PASSING PASSWORD PLACING PLANS POLICY
+ PARALLEL PARSER PARTIAL PARTITION PASSING PASSWORD PERCENT PLACING PLANS POLICY
POSITION PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY
PRIOR PRIVILEGES PROCEDURAL PROCEDURE PROCEDURES PROGRAM PUBLICATION
@@ -11161,7 +11162,7 @@ select_no_parens:
| select_clause sort_clause
{
insertSelectOptions((SelectStmt *) $1, $2, NIL,
- NULL, NULL, NULL,
+ NULL, NULL, NULL, NULL,
yyscanner);
$$ = $1;
}
@@ -11169,6 +11170,7 @@ select_no_parens:
{
insertSelectOptions((SelectStmt *) $1, $2, $3,
list_nth($4, 0), list_nth($4, 1),
+ (list_nth($4, 2)),
NULL,
yyscanner);
$$ = $1;
@@ -11177,6 +11179,7 @@ select_no_parens:
{
insertSelectOptions((SelectStmt *) $1, $2, $4,
list_nth($3, 0), list_nth($3, 1),
+ list_nth($3, 2),
NULL,
yyscanner);
$$ = $1;
@@ -11185,7 +11188,7 @@ select_no_parens:
{
insertSelectOptions((SelectStmt *) $2, NULL, NIL,
NULL, NULL,
- $1,
+ NULL, $1,
yyscanner);
$$ = $2;
}
@@ -11193,7 +11196,7 @@ select_no_parens:
{
insertSelectOptions((SelectStmt *) $2, $3, NIL,
NULL, NULL,
- $1,
+ NULL, $1,
yyscanner);
$$ = $2;
}
@@ -11201,6 +11204,7 @@ select_no_parens:
{
insertSelectOptions((SelectStmt *) $2, $3, $4,
list_nth($5, 0), list_nth($5, 1),
+ list_nth($5, 2),
$1,
yyscanner);
$$ = $2;
@@ -11209,6 +11213,7 @@ select_no_parens:
{
insertSelectOptions((SelectStmt *) $2, $3, $5,
list_nth($4, 0), list_nth($4, 1),
+ list_nth($4, 2),
$1,
yyscanner);
$$ = $2;
@@ -11502,20 +11507,20 @@ sortby: a_expr USING qual_all_Op opt_nulls_order
select_limit:
- limit_clause offset_clause { $$ = list_make2($2, $1); }
- | offset_clause limit_clause { $$ = list_make2($1, $2); }
- | limit_clause { $$ = list_make2(NULL, $1); }
- | offset_clause { $$ = list_make2($1, NULL); }
+ limit_clause offset_clause { $$ = list_make3($2, list_nth($1, 0), list_nth($1, 1)); }
+ | offset_clause limit_clause { $$ = list_make3($1, list_nth($2, 0), list_nth($2, 1)); }
+ | limit_clause { $$ = list_make3(NULL, list_nth($1, 0), list_nth($1, 1)); }
+ | offset_clause { $$ = list_make3($1, NULL, NULL); }
;
opt_select_limit:
select_limit { $$ = $1; }
- | /* EMPTY */ { $$ = list_make2(NULL,NULL); }
+ | /* EMPTY */ { $$ = list_make3(NULL, NULL, NULL); }
;
limit_clause:
LIMIT select_limit_value
- { $$ = $2; }
+ { $$ = list_make2($2, NULL); }
| LIMIT select_limit_value ',' select_offset_value
{
/* Disabled because it was too confusing, bjm 2002-02-18 */
@@ -11533,9 +11538,11 @@ limit_clause:
* we can see the ONLY token in the lookahead slot.
*/
| FETCH first_or_next select_fetch_first_value row_or_rows ONLY
- { $$ = $3; }
+ { $$ = list_make2($3, makeString("EXACT_NUMBER")); }
+ | FETCH first_or_next select_fetch_first_value PERCENT row_or_rows ONLY
+ { $$ = list_make2($3, makeString("PERCENTAGE")); }
| FETCH first_or_next row_or_rows ONLY
- { $$ = makeIntConst(1, -1); }
+ { $$ = list_make2(makeIntConst(1, -1), NULL); }
;
offset_clause:
@@ -15403,6 +15410,7 @@ reserved_keyword:
| ONLY
| OR
| ORDER
+ | PERCENT
| PLACING
| PRIMARY
| REFERENCES
@@ -15786,6 +15794,7 @@ static void
insertSelectOptions(SelectStmt *stmt,
List *sortClause, List *lockingClause,
Node *limitOffset, Node *limitCount,
+ void *limitOption,
WithClause *withClause,
core_yyscan_t yyscanner)
{
@@ -15824,6 +15833,17 @@ insertSelectOptions(SelectStmt *stmt,
parser_errposition(exprLocation(limitCount))));
stmt->limitCount = limitCount;
}
+ if (limitOption)
+ {
+ if (stmt->limitOption)
+ ereport(ERROR,
+ (errcode(ERRCODE_SYNTAX_ERROR),
+ errmsg("multiple LIMIT options not allowed")));
+ if (strcmp(strVal(limitOption), "PERCENTAGE") == 0)
+ stmt->limitOption = PERCENTAGE;
+ else
+ stmt->limitOption = EXACT_NUMBER;
+ }
if (withClause)
{
if (stmt->withClause)
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index c6ce1011e2..6cb5a5dbc4 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -1707,7 +1707,7 @@ transformWhereClause(ParseState *pstate, Node *clause,
* constructName does not affect the semantics, but is used in error messages
*/
Node *
-transformLimitClause(ParseState *pstate, Node *clause,
+transformLimitClause(ParseState *pstate, Node *clause, LimitOption limitOption,
ParseExprKind exprKind, const char *constructName)
{
Node *qual;
@@ -1716,8 +1716,10 @@ transformLimitClause(ParseState *pstate, Node *clause,
return NULL;
qual = transformExpr(pstate, clause, exprKind);
-
- qual = coerce_to_specific_type(pstate, qual, INT8OID, constructName);
+ if (limitOption == PERCENTAGE && (strcmp(constructName, "LIMIT") == 0))
+ qual = coerce_to_specific_type(pstate, qual, FLOAT8OID, constructName);
+ else
+ qual = coerce_to_specific_type(pstate, qual, INT8OID, constructName);
/* LIMIT can't refer to any variables of the current query */
checkExprIsVarFree(pstate, qual, constructName);
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 09f8217c80..e8d7a3351e 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -2289,8 +2289,10 @@ typedef struct LimitState
PlanState ps; /* its first field is NodeTag */
ExprState *limitOffset; /* OFFSET parameter, or NULL if none */
ExprState *limitCount; /* COUNT parameter, or NULL if none */
+ LimitOption limitOption; /* limit specification type */
int64 offset; /* current OFFSET value */
int64 count; /* current COUNT, if any */
+ Tuplestorestate *tuple_store; /* holds the returned tuple */
bool noCount; /* if true, ignore count */
LimitStateCond lstate; /* state machine status, as above */
int64 position; /* 1-based index of last tuple returned */
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index f9389257c6..094c6ee3bb 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -820,4 +820,16 @@ typedef enum OnConflictAction
ONCONFLICT_UPDATE /* ON CONFLICT ... DO UPDATE */
} OnConflictAction;
+/*
+ * LimitOption -
+ * LIMIT option of query
+ *
+ * This is needed in both parsenodes.h and plannodes.h, so put it here...
+ */
+typedef enum LimitOption
+{
+ EXACT_NUMBER, /* LIMIT in exact number of rows */
+ PERCENTAGE /* LIMIT in percentage */
+} LimitOption;
+
#endif /* NODES_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index a7e859dc90..6eb3fe922d 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -159,6 +159,7 @@ typedef struct Query
Node *limitOffset; /* # of result tuples to skip (int8 expr) */
Node *limitCount; /* # of result tuples to return (int8 expr) */
+ LimitOption limitOption; /* limit type */
List *rowMarks; /* a list of RowMarkClause's */
@@ -1583,6 +1584,7 @@ typedef struct SelectStmt
List *sortClause; /* sort clause (a list of SortBy's) */
Node *limitOffset; /* # of result tuples to skip */
Node *limitCount; /* # of result tuples to return */
+ LimitOption limitOption; /* limit type */
List *lockingClause; /* FOR UPDATE (list of LockingClause's) */
WithClause *withClause; /* WITH clause */
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index a008ae07da..fe0fc2f975 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -1775,6 +1775,7 @@ typedef struct LimitPath
Path *subpath; /* path representing input source */
Node *limitOffset; /* OFFSET parameter, or NULL if none */
Node *limitCount; /* COUNT parameter, or NULL if none */
+ LimitOption limitOption; /* LIMIT in percentage or exact number */
} LimitPath;
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 6d087c268f..1cdfa706df 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -946,6 +946,7 @@ typedef struct Limit
Plan plan;
Node *limitOffset; /* OFFSET parameter, or NULL if none */
Node *limitCount; /* COUNT parameter, or NULL if none */
+ LimitOption limitOption; /* LIMIT in percentage or exact number */
} Limit;
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 574bb85b50..fe593170d3 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -264,6 +264,7 @@ extern ModifyTablePath *create_modifytable_path(PlannerInfo *root,
extern LimitPath *create_limit_path(PlannerInfo *root, RelOptInfo *rel,
Path *subpath,
Node *limitOffset, Node *limitCount,
+ LimitOption limitOption,
int64 offset_est, int64 count_est);
extern Path *reparameterize_path(PlannerInfo *root, Path *path,
diff --git a/src/include/optimizer/planmain.h b/src/include/optimizer/planmain.h
index 3bbdb5e2f7..6f21cd076a 100644
--- a/src/include/optimizer/planmain.h
+++ b/src/include/optimizer/planmain.h
@@ -56,7 +56,7 @@ extern Agg *make_agg(List *tlist, List *qual,
int numGroupCols, AttrNumber *grpColIdx, Oid *grpOperators,
List *groupingSets, List *chain,
double dNumGroups, Plan *lefttree);
-extern Limit *make_limit(Plan *lefttree, Node *limitOffset, Node *limitCount);
+extern Limit *make_limit(Plan *lefttree, Node *limitOffset, Node *limitCount, LimitOption limitOption);
/*
* prototypes for plan/initsplan.c
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index f05444008c..0a80bb9b76 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -299,6 +299,7 @@ PG_KEYWORD("partial", PARTIAL, UNRESERVED_KEYWORD)
PG_KEYWORD("partition", PARTITION, UNRESERVED_KEYWORD)
PG_KEYWORD("passing", PASSING, UNRESERVED_KEYWORD)
PG_KEYWORD("password", PASSWORD, UNRESERVED_KEYWORD)
+PG_KEYWORD("percent", PERCENT, RESERVED_KEYWORD)
PG_KEYWORD("placing", PLACING, RESERVED_KEYWORD)
PG_KEYWORD("plans", PLANS, UNRESERVED_KEYWORD)
PG_KEYWORD("policy", POLICY, UNRESERVED_KEYWORD)
diff --git a/src/include/parser/parse_clause.h b/src/include/parser/parse_clause.h
index 179f3ab3c3..39a74c32d2 100644
--- a/src/include/parser/parse_clause.h
+++ b/src/include/parser/parse_clause.h
@@ -22,7 +22,7 @@ extern int setTargetTable(ParseState *pstate, RangeVar *relation,
extern Node *transformWhereClause(ParseState *pstate, Node *clause,
ParseExprKind exprKind, const char *constructName);
-extern Node *transformLimitClause(ParseState *pstate, Node *clause,
+extern Node *transformLimitClause(ParseState *pstate, Node *clause, LimitOption limitOption,
ParseExprKind exprKind, const char *constructName);
extern List *transformGroupClause(ParseState *pstate, List *grouplist,
List **groupingSets,
diff --git a/src/test/modules/test_ddl_deparse/expected/create_table.out b/src/test/modules/test_ddl_deparse/expected/create_table.out
index 2d7dfd533e..eb04e36aac 100644
--- a/src/test/modules/test_ddl_deparse/expected/create_table.out
+++ b/src/test/modules/test_ddl_deparse/expected/create_table.out
@@ -105,7 +105,7 @@ CREATE TABLE student (
) INHERITS (person);
NOTICE: DDL test: type simple, tag CREATE TABLE
CREATE TABLE stud_emp (
- percent int4
+ "percent" int4
) INHERITS (emp, student);
NOTICE: merging multiple inherited definitions of column "id"
NOTICE: merging multiple inherited definitions of column "name"
diff --git a/src/test/modules/test_ddl_deparse/sql/create_table.sql b/src/test/modules/test_ddl_deparse/sql/create_table.sql
index dd3a908638..f158dd4296 100644
--- a/src/test/modules/test_ddl_deparse/sql/create_table.sql
+++ b/src/test/modules/test_ddl_deparse/sql/create_table.sql
@@ -94,7 +94,7 @@ CREATE TABLE student (
) INHERITS (person);
CREATE TABLE stud_emp (
- percent int4
+ "percent" int4
) INHERITS (emp, student);
diff --git a/src/test/regress/expected/create_table.out b/src/test/regress/expected/create_table.out
index d51e547278..d2055f21cd 100644
--- a/src/test/regress/expected/create_table.out
+++ b/src/test/regress/expected/create_table.out
@@ -79,7 +79,7 @@ CREATE TABLE student (
gpa float8
) INHERITS (person);
CREATE TABLE stud_emp (
- percent int4
+ "percent" int4
) INHERITS (emp, student);
NOTICE: merging multiple inherited definitions of column "name"
NOTICE: merging multiple inherited definitions of column "age"
diff --git a/src/test/regress/expected/limit.out b/src/test/regress/expected/limit.out
index c18f547cbd..fcadc92f5d 100644
--- a/src/test/regress/expected/limit.out
+++ b/src/test/regress/expected/limit.out
@@ -108,6 +108,61 @@ SELECT ''::text AS five, unique1, unique2, stringu1
| 904 | 793 | UIAAAA
(5 rows)
+--
+-- PERCENT
+-- Check the PERCENT option of limit clause
+--
+SELECT ''::text AS two, unique1, unique2, stringu1
+ FROM onek WHERE unique1 > 50
+ ORDER BY unique1 FETCH FIRST 1 PERCENT ROWS ONLY;
+ two | unique1 | unique2 | stringu1
+-----+---------+---------+----------
+ | 51 | 76 | ZBAAAA
+ | 52 | 985 | ACAAAA
+ | 53 | 196 | BCAAAA
+ | 54 | 356 | CCAAAA
+ | 55 | 627 | DCAAAA
+ | 56 | 54 | ECAAAA
+ | 57 | 942 | FCAAAA
+ | 58 | 114 | GCAAAA
+ | 59 | 593 | HCAAAA
+(9 rows)
+
+SELECT ''::text AS two, unique1, unique2, stringu1
+ FROM onek WHERE unique1 > 60 AND unique1 < 63
+ ORDER BY unique1 FETCH FIRST 50 PERCENT ROWS ONLY;
+ two | unique1 | unique2 | stringu1
+-----+---------+---------+----------
+ | 61 | 560 | JCAAAA
+(1 row)
+
+SELECT ''::text AS three, unique1, unique2, stringu1
+ FROM onek WHERE unique1 > 100
+ ORDER BY unique1 FETCH FIRST 1 PERCENT ROWS ONLY OFFSET 20;
+ three | unique1 | unique2 | stringu1
+-------+---------+---------+----------
+ | 121 | 700 | REAAAA
+ | 122 | 519 | SEAAAA
+ | 123 | 777 | TEAAAA
+ | 124 | 503 | UEAAAA
+ | 125 | 849 | VEAAAA
+ | 126 | 330 | WEAAAA
+ | 127 | 511 | XEAAAA
+ | 128 | 721 | YEAAAA
+(8 rows)
+
+SELECT ''::text AS eleven, unique1, unique2, stringu1
+ FROM onek WHERE unique1 < 50
+ ORDER BY unique1 DESC FETCH FIRST 10 PERCENT ROWS ONLY OFFSET 39;
+ eleven | unique1 | unique2 | stringu1
+--------+---------+---------+----------
+ | 10 | 520 | KAAAAA
+ | 9 | 49 | JAAAAA
+ | 8 | 653 | IAAAAA
+ | 7 | 647 | HAAAAA
+ | 6 | 978 | GAAAAA
+(5 rows)
+
-- Test null limit and offset. The planner would discard a simple null
-- constant, so to ensure executor is exercised, do this:
select * from int8_tbl limit (case when random() < 0.5 then null::bigint end);
@@ -286,6 +341,43 @@ fetch all in c4;
----+----
(0 rows)
+declare c6 cursor for select * from int8_tbl fetch first 50 percent rows only;
+fetch all in c6;
+ q1 | q2
+-----+------------------
+ 123 | 456
+ 123 | 4567890123456789
+(2 rows)
+
+fetch 1 in c6;
+ q1 | q2
+----+----
+(0 rows)
+
+fetch backward 1 in c6;
+ q1 | q2
+-----+------------------
+ 123 | 4567890123456789
+(1 row)
+
+fetch backward all in c6;
+ q1 | q2
+-----+-----
+ 123 | 456
+(1 row)
+
+fetch backward 1 in c6;
+ q1 | q2
+----+----
+(0 rows)
+
+fetch all in c6;
+ q1 | q2
+-----+------------------
+ 123 | 456
+ 123 | 4567890123456789
+(2 rows)
+
rollback;
-- Stress test for variable LIMIT in conjunction with bounded-heap sorting
SELECT
@@ -503,3 +595,19 @@ select sum(tenthous) as s1, sum(tenthous) + random()*0 as s2
45020 | 45020
(3 rows)
+select sum(tenthous) as s1, sum(tenthous) + random()*0 as s2
+ from tenk1 group by thousand order by thousand FETCH FIRST 1 PERCENT ROWS ONLY;
+ s1 | s2
+-------+-------
+ 45000 | 45000
+ 45010 | 45010
+ 45020 | 45020
+ 45030 | 45030
+ 45040 | 45040
+ 45050 | 45050
+ 45060 | 45060
+ 45070 | 45070
+ 45080 | 45080
+ 45090 | 45090
+(10 rows)
+
diff --git a/src/test/regress/sql/create_table.sql b/src/test/regress/sql/create_table.sql
index 4091c19cf0..a759ab5717 100644
--- a/src/test/regress/sql/create_table.sql
+++ b/src/test/regress/sql/create_table.sql
@@ -92,7 +92,7 @@ CREATE TABLE student (
CREATE TABLE stud_emp (
- percent int4
+ "percent" int4
) INHERITS (emp, student);
diff --git a/src/test/regress/sql/limit.sql b/src/test/regress/sql/limit.sql
index 2a313d80ca..6609f8eb21 100644
--- a/src/test/regress/sql/limit.sql
+++ b/src/test/regress/sql/limit.sql
@@ -30,6 +30,24 @@ SELECT ''::text AS five, unique1, unique2, stringu1
SELECT ''::text AS five, unique1, unique2, stringu1
FROM onek
ORDER BY unique1 LIMIT 5 OFFSET 900;
+--
+-- PERCENT
+-- Check the PERCENT option of limit clause
+--
+
+SELECT ''::text AS two, unique1, unique2, stringu1
+ FROM onek WHERE unique1 > 50
+ ORDER BY unique1 FETCH FIRST 1 PERCENT ROWS ONLY;
+SELECT ''::text AS two, unique1, unique2, stringu1
+ FROM onek WHERE unique1 > 60 AND unique1 < 63
+ ORDER BY unique1 FETCH FIRST 50 PERCENT ROWS ONLY;
+SELECT ''::text AS three, unique1, unique2, stringu1
+ FROM onek WHERE unique1 > 100
+ ORDER BY unique1 FETCH FIRST 1 PERCENT ROWS ONLY OFFSET 20;
+SELECT ''::text AS eleven, unique1, unique2, stringu1
+ FROM onek WHERE unique1 < 50
+ ORDER BY unique1 DESC FETCH FIRST 10 PERCENT ROWS ONLY OFFSET 39;
+
-- Test null limit and offset. The planner would discard a simple null
-- constant, so to ensure executor is exercised, do this:
@@ -38,7 +56,6 @@ select * from int8_tbl offset (case when random() < 0.5 then null::bigint end);
-- Test assorted cases involving backwards fetch from a LIMIT plan node
begin;
-
declare c1 cursor for select * from int8_tbl limit 10;
fetch all in c1;
fetch 1 in c1;
@@ -71,6 +88,15 @@ fetch backward all in c4;
fetch backward 1 in c4;
fetch all in c4;
+
+declare c6 cursor for select * from int8_tbl fetch first 50 percent rows only;
+fetch all in c6;
+fetch 1 in c6;
+fetch backward 1 in c6;
+fetch backward all in c6;
+fetch backward 1 in c6;
+fetch all in c6;
+
rollback;
-- Stress test for variable LIMIT in conjunction with bounded-heap sorting
@@ -141,3 +167,6 @@ select sum(tenthous) as s1, sum(tenthous) + random()*0 as s2
select sum(tenthous) as s1, sum(tenthous) + random()*0 as s2
from tenk1 group by thousand order by thousand limit 3;
+
+select sum(tenthous) as s1, sum(tenthous) + random()*0 as s2
+ from tenk1 group by thousand order by thousand FETCH FIRST 1 PERCENT ROWS ONLY;
