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Add a planner support function for numeric generate_series().
This allows the planner to estimate the number of rows returned by generate_series(numeric, numeric[, numeric]), when the input values can be estimated at plan time. Song Jinzhou, reviewed by Dean Rasheed and David Rowley. Discussion: https://postgr.es/m/tencent_F43E7F4DD50EF5986D1051DE8DE547910206%40qq.com Discussion: https://postgr.es/m/tencent_1F6D5B9A1545E02FD7D0EE508DFD056DE50A%40qq.com
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5 files changed

+232
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‎src/backend/utils/adt/numeric.c‎

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Original file line numberDiff line numberDiff line change
@@ -34,6 +34,7 @@
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#include "miscadmin.h"
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#include "nodes/nodeFuncs.h"
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#include "nodes/supportnodes.h"
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#include "optimizer/optimizer.h"
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#include "utils/array.h"
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#include "utils/builtins.h"
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#include "utils/float.h"
@@ -1827,6 +1828,126 @@ generate_series_step_numeric(PG_FUNCTION_ARGS)
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SRF_RETURN_DONE(funcctx);
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}
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/*
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* Planner support function for generate_series(numeric, numeric [, numeric])
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*/
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Datum
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generate_series_numeric_support(PG_FUNCTION_ARGS)
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{
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Node *rawreq = (Node *) PG_GETARG_POINTER(0);
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Node *ret = NULL;
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if (IsA(rawreq, SupportRequestRows))
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{
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/* Try to estimate the number of rows returned */
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SupportRequestRows *req = (SupportRequestRows *) rawreq;
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if (is_funcclause(req->node)) /* be paranoid */
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{
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List *args = ((FuncExpr *) req->node)->args;
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Node *arg1,
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*arg2,
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*arg3;
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/* We can use estimated argument values here */
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arg1 = estimate_expression_value(req->root, linitial(args));
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arg2 = estimate_expression_value(req->root, lsecond(args));
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if (list_length(args) >= 3)
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arg3 = estimate_expression_value(req->root, lthird(args));
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else
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arg3 = NULL;
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/*
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* If any argument is constant NULL, we can safely assume that
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* zero rows are returned. Otherwise, if they're all non-NULL
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* constants, we can calculate the number of rows that will be
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* returned.
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*/
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if ((IsA(arg1, Const) &&
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((Const *) arg1)->constisnull) ||
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(IsA(arg2, Const) &&
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((Const *) arg2)->constisnull) ||
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(arg3 != NULL && IsA(arg3, Const) &&
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((Const *) arg3)->constisnull))
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{
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req->rows = 0;
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ret = (Node *) req;
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}
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else if (IsA(arg1, Const) &&
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IsA(arg2, Const) &&
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(arg3 == NULL || IsA(arg3, Const)))
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{
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Numeric start_num;
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Numeric stop_num;
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NumericVar step = const_one;
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/*
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* If any argument is NaN or infinity, generate_series() will
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* error out, so we needn't produce an estimate.
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*/
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start_num = DatumGetNumeric(((Const *) arg1)->constvalue);
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stop_num = DatumGetNumeric(((Const *) arg2)->constvalue);
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if (NUMERIC_IS_SPECIAL(start_num) ||
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NUMERIC_IS_SPECIAL(stop_num))
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PG_RETURN_POINTER(NULL);
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if (arg3)
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{
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Numeric step_num;
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step_num = DatumGetNumeric(((Const *) arg3)->constvalue);
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if (NUMERIC_IS_SPECIAL(step_num))
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PG_RETURN_POINTER(NULL);
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init_var_from_num(step_num, &step);
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}
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/*
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* The number of rows that will be returned is given by
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* floor((stop - start) / step) + 1, if the sign of step
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* matches the sign of stop - start. Otherwise, no rows will
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* be returned.
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*/
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if (cmp_var(&step, &const_zero) != 0)
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{
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NumericVar start;
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NumericVar stop;
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NumericVar res;
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init_var_from_num(start_num, &start);
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init_var_from_num(stop_num, &stop);
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init_var(&res);
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sub_var(&stop, &start, &res);
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if (step.sign != res.sign)
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{
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/* no rows will be returned */
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req->rows = 0;
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ret = (Node *) req;
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}
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else
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{
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if (arg3)
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div_var(&res, &step, &res, 0, false, false);
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else
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trunc_var(&res, 0); /* step = 1 */
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req->rows = numericvar_to_double_no_overflow(&res) + 1;
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ret = (Node *) req;
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}
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free_var(&res);
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}
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}
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}
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}
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PG_RETURN_POINTER(ret);
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}
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18301951

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/*
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* Implements the numeric version of the width_bucket() function

‎src/include/catalog/catversion.h‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -57,6 +57,6 @@
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*/
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/* yyyymmddN */
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#define CATALOG_VERSION_NO 202411111
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#define CATALOG_VERSION_NO 202412021
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#endif

‎src/include/catalog/pg_proc.dat‎

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Original file line numberDiff line numberDiff line change
@@ -8464,13 +8464,18 @@
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proname => 'generate_series_int8_support', prorettype => 'internal',
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proargtypes => 'internal', prosrc => 'generate_series_int8_support' },
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{ oid => '3259', descr => 'non-persistent series generator',
8467-
proname => 'generate_series', prorows => '1000', proretset => 't',
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proname => 'generate_series', prorows => '1000',
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prosupport => 'generate_series_numeric_support', proretset => 't',
84688469
prorettype => 'numeric', proargtypes => 'numeric numeric numeric',
84698470
prosrc => 'generate_series_step_numeric' },
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{ oid => '3260', descr => 'non-persistent series generator',
8471-
proname => 'generate_series', prorows => '1000', proretset => 't',
8472+
proname => 'generate_series', prorows => '1000',
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prosupport => 'generate_series_numeric_support', proretset => 't',
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prorettype => 'numeric', proargtypes => 'numeric numeric',
84738475
prosrc => 'generate_series_numeric' },
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{ oid => '8405', descr => 'planner support for generate_series',
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proname => 'generate_series_numeric_support', prorettype => 'internal',
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proargtypes => 'internal', prosrc => 'generate_series_numeric_support' },
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{ oid => '938', descr => 'non-persistent series generator',
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proname => 'generate_series', prorows => '1000',
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prosupport => 'generate_series_timestamp_support', proretset => 't',

‎src/test/regress/expected/misc_functions.out‎

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@@ -712,6 +712,71 @@ false, true, false, true);
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-- the support function.
713713
SELECT * FROM generate_series(TIMESTAMPTZ '2024-02-01', TIMESTAMPTZ '2024-03-01', INTERVAL '0 day') g(s);
714714
ERROR: step size cannot equal zero
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--
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-- Test the SupportRequestRows support function for generate_series_numeric()
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--
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-- Ensure the row estimate matches the actual rows
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SELECT explain_mask_costs($$
720+
SELECT * FROM generate_series(1.0, 25.0) g(s);$$,
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true, true, false, true);
722+
explain_mask_costs
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------------------------------------------------------------------------------------------
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Function Scan on generate_series g (cost=N..N rows=25 width=N) (actual rows=25 loops=1)
725+
(1 row)
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-- As above but with non-default step
728+
SELECT explain_mask_costs($$
729+
SELECT * FROM generate_series(1.0, 25.0, 2.0) g(s);$$,
730+
true, true, false, true);
731+
explain_mask_costs
732+
------------------------------------------------------------------------------------------
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Function Scan on generate_series g (cost=N..N rows=13 width=N) (actual rows=13 loops=1)
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(1 row)
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-- Ensure the estimates match when step is decreasing
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SELECT explain_mask_costs($$
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SELECT * FROM generate_series(25.0, 1.0, -1.0) g(s);$$,
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true, true, false, true);
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explain_mask_costs
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------------------------------------------------------------------------------------------
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Function Scan on generate_series g (cost=N..N rows=25 width=N) (actual rows=25 loops=1)
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(1 row)
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-- Ensure an empty range estimates 1 row
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SELECT explain_mask_costs($$
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SELECT * FROM generate_series(25.0, 1.0, 1.0) g(s);$$,
748+
true, true, false, true);
749+
explain_mask_costs
750+
----------------------------------------------------------------------------------------
751+
Function Scan on generate_series g (cost=N..N rows=1 width=N) (actual rows=0 loops=1)
752+
(1 row)
753+
754+
-- Ensure we get the default row estimate for error cases (infinity/NaN values
755+
-- and zero step size)
756+
SELECT explain_mask_costs($$
757+
SELECT * FROM generate_series('-infinity'::NUMERIC, 'infinity'::NUMERIC, 1.0) g(s);$$,
758+
false, true, false, true);
759+
explain_mask_costs
760+
-------------------------------------------------------------------
761+
Function Scan on generate_series g (cost=N..N rows=1000 width=N)
762+
(1 row)
763+
764+
SELECT explain_mask_costs($$
765+
SELECT * FROM generate_series(1.0, 25.0, 'NaN'::NUMERIC) g(s);$$,
766+
false, true, false, true);
767+
explain_mask_costs
768+
-------------------------------------------------------------------
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Function Scan on generate_series g (cost=N..N rows=1000 width=N)
770+
(1 row)
771+
772+
SELECT explain_mask_costs($$
773+
SELECT * FROM generate_series(25.0, 2.0, 0.0) g(s);$$,
774+
false, true, false, true);
775+
explain_mask_costs
776+
-------------------------------------------------------------------
777+
Function Scan on generate_series g (cost=N..N rows=1000 width=N)
778+
(1 row)
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715780
-- Test functions for control data
716781
SELECT count(*) > 0 AS ok FROM pg_control_checkpoint();
717782
ok

‎src/test/regress/sql/misc_functions.sql‎

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Original file line numberDiff line numberDiff line change
@@ -311,6 +311,44 @@ false, true, false, true);
311311
-- the support function.
312312
SELECT * FROM generate_series(TIMESTAMPTZ '2024-02-01', TIMESTAMPTZ '2024-03-01', INTERVAL '0 day') g(s);
313313

314+
--
315+
-- Test the SupportRequestRows support function for generate_series_numeric()
316+
--
317+
318+
-- Ensure the row estimate matches the actual rows
319+
SELECT explain_mask_costs($$
320+
SELECT * FROM generate_series(1.0, 25.0) g(s);$$,
321+
true, true, false, true);
322+
323+
-- As above but with non-default step
324+
SELECT explain_mask_costs($$
325+
SELECT * FROM generate_series(1.0, 25.0, 2.0) g(s);$$,
326+
true, true, false, true);
327+
328+
-- Ensure the estimates match when step is decreasing
329+
SELECT explain_mask_costs($$
330+
SELECT * FROM generate_series(25.0, 1.0, -1.0) g(s);$$,
331+
true, true, false, true);
332+
333+
-- Ensure an empty range estimates 1 row
334+
SELECT explain_mask_costs($$
335+
SELECT * FROM generate_series(25.0, 1.0, 1.0) g(s);$$,
336+
true, true, false, true);
337+
338+
-- Ensure we get the default row estimate for error cases (infinity/NaN values
339+
-- and zero step size)
340+
SELECT explain_mask_costs($$
341+
SELECT * FROM generate_series('-infinity'::NUMERIC, 'infinity'::NUMERIC, 1.0) g(s);$$,
342+
false, true, false, true);
343+
344+
SELECT explain_mask_costs($$
345+
SELECT * FROM generate_series(1.0, 25.0, 'NaN'::NUMERIC) g(s);$$,
346+
false, true, false, true);
347+
348+
SELECT explain_mask_costs($$
349+
SELECT * FROM generate_series(25.0, 2.0, 0.0) g(s);$$,
350+
false, true, false, true);
351+
314352
-- Test functions for control data
315353
SELECT count(*) > 0 AS ok FROM pg_control_checkpoint();
316354
SELECT count(*) > 0 AS ok FROM pg_control_init();

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