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Commitf739992

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tablefunc: Reject negative number of tuples passed to normal_rand()
The function converted the first argument i.e. the number of tuples toreturn into an unsigned integer which turns out to be huge number whena negative value is passed. This causes the function to take muchlonger time to execute. Instead, reject a negative value.(If someone really wants to generate many more result rows, theyshould consider adding a bigint or numeric variant.)While at it, improve SQL test to test the number of tuples returned bythis function.Author: Ashutosh Bapat <ashutosh.bapat@2ndquadrant.com>Discussion:https://www.postgresql.org/message-id/CAG-ACPW3PUUmSnM6cLa9Rw4BEC5cEMKjX8Gogc8gvQcT3cYA1A@mail.gmail.com
1 parent2fbd786 commitf739992

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3 files changed

+18
-6
lines changed

3 files changed

+18
-6
lines changed

‎contrib/tablefunc/expected/tablefunc.out

Lines changed: 7 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -3,12 +3,15 @@ CREATE EXTENSION tablefunc;
33
-- normal_rand()
44
-- no easy way to do this for regression testing
55
--
6-
SELECT avg(normal_rand)::int FROM normal_rand(100, 250, 0.2);
7-
avg
8-
-----
9-
250
6+
SELECT avg(normal_rand)::int, count(*) FROM normal_rand(100, 250, 0.2);
7+
avg| count
8+
-----+-------
9+
250 | 100
1010
(1 row)
1111

12+
-- negative number of tuples
13+
SELECT avg(normal_rand)::int, count(*) FROM normal_rand(-1, 250, 0.2);
14+
ERROR: number of rows cannot be negative
1215
--
1316
-- crosstab()
1417
--

‎contrib/tablefunc/sql/tablefunc.sql

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -4,7 +4,9 @@ CREATE EXTENSION tablefunc;
44
-- normal_rand()
55
-- no easy way to do this for regression testing
66
--
7-
SELECTavg(normal_rand)::intFROM normal_rand(100,250,0.2);
7+
SELECTavg(normal_rand)::int,count(*)FROM normal_rand(100,250,0.2);
8+
-- negative number of tuples
9+
SELECTavg(normal_rand)::int,count(*)FROM normal_rand(-1,250,0.2);
810

911
--
1012
-- crosstab()

‎contrib/tablefunc/tablefunc.c

Lines changed: 8 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -184,6 +184,8 @@ normal_rand(PG_FUNCTION_ARGS)
184184
/* stuff done only on the first call of the function */
185185
if (SRF_IS_FIRSTCALL())
186186
{
187+
int32num_tuples;
188+
187189
/* create a function context for cross-call persistence */
188190
funcctx=SRF_FIRSTCALL_INIT();
189191

@@ -193,7 +195,12 @@ normal_rand(PG_FUNCTION_ARGS)
193195
oldcontext=MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
194196

195197
/* total number of tuples to be returned */
196-
funcctx->max_calls=PG_GETARG_UINT32(0);
198+
num_tuples=PG_GETARG_INT32(0);
199+
if (num_tuples<0)
200+
ereport(ERROR,
201+
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
202+
errmsg("number of rows cannot be negative")));
203+
funcctx->max_calls=num_tuples;
197204

198205
/* allocate memory for user context */
199206
fctx= (normal_rand_fctx*)palloc(sizeof(normal_rand_fctx));

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