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|
--echo #
--echo # Bug#26136509 ADD A MAX_RECURSION VARIABLE TO LIMIT RECURSION IN CTES
--echo #
SELECT @@cte_max_recursion_depth;
# UNION ALL then UNION DISTINCT
let $c=2;
while ($c)
{
if ($c == 2)
{
let $union=ALL;
}
if ($c == 1)
{
let $union=DISTINCT;
}
dec $c;
# One recursive query block which generates 1 row per input row.
# With the @m variable, we control how many iterations this query will
# want to do. By varying @m we can thus make it hit the cap or not.
let $q=
WITH RECURSIVE qn AS (
SELECT 1 AS a UNION $union
SELECT 1+a FROM qn WHERE a<@m)
SELECT COUNT(*) FROM qn;
SET @m = 1001;
--error ER_CTE_MAX_RECURSION_DEPTH
eval $q;
SET @m = 1000;
eval $q;
SET cte_max_recursion_depth=10;
SET @m = 11;
--error ER_CTE_MAX_RECURSION_DEPTH
eval $q;
SET @m = 10;
eval $q;
set cte_max_recursion_depth=default;
# 3 recursive query blocks. Each of them operates on its own data only.
let $q=
WITH RECURSIVE qn AS
(SELECT 1 AS a, 0 AS b UNION $union
SELECT 1+a, 1 FROM qn WHERE b IN (0,1) AND a<@m UNION $union
SELECT 1+a, 2 FROM qn WHERE b IN (0,2) AND a<@m UNION $union
SELECT 1+a, 3 FROM qn WHERE b IN (0,3) AND a<@m
) SELECT COUNT(*) FROM qn;
SET @m = 1001;
--error ER_CTE_MAX_RECURSION_DEPTH
eval $q;
SET @m = 999;
eval $q;
# You may wonder why there is a difference of 2, instead of 1, in the
# above values of @m. It is because with @m=1000, UNION ALL will throw
# error, while DISTINCT will not; which is because in UNION ALL, the
# first recursive query blocks need an extra pass over what the last
# one has produced, whereas in UNION DISTINCT, the three blocks walk
# in lock-step. So the count of iterations is higher for ALL. This
# difference is bounded by the number of query blocks, which is small
# enough. cte_max_recursion_depth does not intend to be 100% exact.
SET cte_max_recursion_depth=10;
SET @m = 11;
--error ER_CTE_MAX_RECURSION_DEPTH
eval $q;
SET @m = 9;
eval $q;
SET cte_max_recursion_depth=DEFAULT;
# One recursive query block which generates 2 rows per input row.
# Each iteration thus generates twice more rows than the previous.
let $q=
WITH RECURSIVE
onetwo(b) AS (SELECT 1 UNION SELECT 2),
qn AS (
SELECT 1 AS a, 0 AS b UNION $union
SELECT 1+a, onetwo.b FROM onetwo, qn WHERE a<@m)
SELECT COUNT(*) FROM qn;
SET cte_max_recursion_depth=10;
SET @m = 11;
--error ER_CTE_MAX_RECURSION_DEPTH
eval $q;
SET @m = 10;
eval $q;
SET cte_max_recursion_depth=default;
}
# Test that we can block any recursive query
SET cte_max_recursion_depth=0;
--error ER_CTE_MAX_RECURSION_DEPTH
WITH RECURSIVE qn AS (
SELECT 1 AS a UNION ALL
SELECT 1+a FROM qn WHERE a<0)
SELECT COUNT(*) FROM qn;
|
