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Fix segmentation fault of SUBSTRING (#1903) #1915

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merged 2 commits into from
Jun 2, 2021
Merged

Fix segmentation fault of SUBSTRING (#1903) #1915

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ca938f8
cherry pick #1903 to release-5.0
leiysky May 17, 2021
d7db443
Merge branch 'release-5.0' into release-5.0-b40059d50ca7
zhouqiang-cl Jun 1, 2021
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15 changes: 12 additions & 3 deletions dbms/src/Functions/FunctionsString.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -481,14 +481,14 @@ struct SubstringUTF8Impl
ColumnString::Offset bytes_start = 0;
ColumnString::Offset bytes_length = 0;
size_t start = 0;
if(original_start >= 0)
if (original_start >= 0)
start = original_start;
else
{
// set the start as string_length - abs(original_start) + 1
std::vector<ColumnString::Offset> start_offsets;
ColumnString::Offset current = prev_offset;
while (current < offsets[i] -1)
while (current < offsets[i] - 1)
{
start_offsets.push_back(current);
if (data[current] < 0xBF)
Expand All @@ -500,9 +500,18 @@ struct SubstringUTF8Impl
else
current += 1;
}
if (static_cast<size_t>(-original_start) > start_offsets.size())
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do we have test when original_start == INT64_MIN?

@windtalker

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No, so we should check it explicitly here.

{
// return empty string
res_data.resize(res_data.size() + 1);
res_data[res_offset] = 0;
res_offset++;
res_offsets[i] = res_offset;
continue;
}
start = start_offsets.size() + original_start + 1;
pos = start;
j = start_offsets[start-1];
j = start_offsets[start - 1];
}
while (j < offsets[i] - 1)
{
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23 changes: 23 additions & 0 deletions tests/fullstack-test/expr/substring_utf8.test
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@@ -0,0 +1,23 @@
mysql> drop table if exists test.t
mysql> create table test.t(a char(10))
mysql> insert into test.t values(''), ('abc')
mysql> alter table test.t set tiflash replica 1

func> wait_table test t

mysql> set session tidb_isolation_read_engines='tiflash'; set tidb_allow_mpp=0; select * from test.t where substring(a, -3, 4) = 'abc'
a
abc

mysql> set session tidb_isolation_read_engines='tiflash'; set tidb_allow_mpp=0; select * from test.t where substring(a, -3, 2) = 'ab'
a
abc

mysql> set session tidb_isolation_read_engines='tiflash'; set tidb_allow_mpp=0; select * from test.t where substring(a, -4, 3) = 'abc'
# Empty

mysql> set session tidb_isolation_read_engines='tiflash'; set tidb_allow_mpp=0; select count(*) from test.t where substring(a, 0, 3) = '' order by a
count(*)
2

mysql> drop table if exists test.t