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Merge pull request #45816 from ClickHouse/minor-doc-fixes

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Minor doc follow-up to #45382
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Robert Schulze 2023-01-31 11:32:48 +01:00 committed by GitHub
commit 170fff16e4
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2 changed files with 15 additions and 15 deletions
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10
docs/en/sql-reference/functions/string-search-functions.md
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@ -95,11 +95,11 @@ Result:
└───────────────────────────────┘
```
Note: If argument needle is empty the following rules apply:
- if no start_pos was specified: return 1
- if start_pos = 0: return 1
- if start_pos >= 1 and start_pos <= length(haystack) + 1: return start_pos
- otherwise: return 0
If argument `needle` is empty the following rules apply:
- if no `start_pos` was specified: return `1`
- if `start_pos = 0`: return `1`
- if `start_pos >= 1` and `start_pos <= length(haystack) + 1`: return `start_pos`
- otherwise: return `0`
The same rules also apply to functions `positionCaseInsensitive`, `positionUTF8` and `positionCaseInsensitiveUTF8`

20
src/Functions/PositionImpl.h
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@ -202,14 +202,14 @@ struct PositionImpl
const UInt8 * const end = haystack_data.data() + haystack_data.size();
const UInt8 * pos = begin;
/// Fastpath when needle is empty
/// Fast path when needle is empty
if (needle.empty())
{
/// When needle is empty and start_pos doesn't exist, always return 1
/// Needle is empty and start_pos doesn't exist --> always return 1
if (start_pos == nullptr)
{
for (auto & x : res)
x = 1;
for (auto & r : res)
r = 1;
return;
}
@ -218,13 +218,13 @@ struct PositionImpl
if (const ColumnConst * start_pos_const = typeid_cast<const ColumnConst *>(&*start_pos))
{
/// When needle is empty and start_pos is constant
UInt64 start = std::max(start_pos_const->getUInt(0), UInt64(1));
/// Needle is empty and start_pos is constant
UInt64 start = std::max(start_pos_const->getUInt(0), static_cast<UInt64>(1));
for (size_t i = 0; i < rows; ++i)
{
size_t haystack_size = Impl::countChars(
reinterpret_cast<const char *>(pos), reinterpret_cast<const char *>(pos + haystack_offsets[i] - prev_offset - 1));
res[i] = start <= haystack_size + 1 ? start : 0;
res[i] = (start <= haystack_size + 1) ? start : 0;
pos = begin + haystack_offsets[i];
prev_offset = haystack_offsets[i];
@ -233,14 +233,14 @@ struct PositionImpl
}
else
{
/// When needle is empty and start_pos is not constant
/// Needle is empty and start_pos is not constant
for (size_t i = 0; i < rows; ++i)
{
size_t haystack_size = Impl::countChars(
reinterpret_cast<const char *>(pos), reinterpret_cast<const char *>(pos + haystack_offsets[i] - prev_offset - 1));
UInt64 start = start_pos->getUInt(i);
start = std::max(UInt64(1), start);
res[i] = start <= haystack_size + 1 ? start : 0;
start = std::max(static_cast<UInt64>(1), start);
res[i] = (start <= haystack_size + 1) ? start : 0;
pos = begin + haystack_offsets[i];
prev_offset = haystack_offsets[i];