xiaokang commented on code in PR #10169:
URL: https://github.com/apache/doris/pull/10169#discussion_r904424703
##########
be/src/vec/functions/like.cpp:
##########
@@ -129,6 +130,42 @@ Status FunctionLikeBase::vector_vector(const
ColumnString::Chars& values,
const ColumnString::Offsets&
pattern_offsets,
ColumnUInt8::Container& result, const
LikeFn& function,
LikeSearchState* search_state) {
+ // for constant_substring_fn, use long run length search for performance
+ if (constant_substring_fn ==
+ *(function.target<doris::Status (*)(LikeSearchState * state, const
StringValue&,
+ const StringValue&, unsigned
char*)>())) {
+ // treat continous multi string data as a long string data
+ const UInt8* begin = values.data();
+ const UInt8* end = begin + values.size();
+ const UInt8* pos = begin;
+
+ /// Current index in the array of strings.
+ size_t i = 0;
+ size_t needle_size =
search_state->substring_pattern.get_pattern_length();
+
+ /// We will search for the next occurrence in all strings at once.
+ while (pos < end) {
+ // search return matched substring start offset
+ pos = (UInt8*)search_state->substring_pattern.search((char*)pos,
end - pos);
+ if (pos >= end) break;
+
+ /// Determine which index it refers to.
+ /// begin + value_offsets[i] is the start offset of string at i+1
+ while (begin + value_offsets[i] <= pos) ++i;
+
+ /// We check that the entry does not pass through the boundaries
of strings.
Review Comment:
It's necessary to check the boundary.
Here is an example:
pattern: "cdef"
row1: "abcd"
row2: "efgh"
values.data: "abcdefgh"
value_offsets: [4, 8]
values.data "abcdefgh" will match pattern "cdef" at pos 2. The end of
matched substring is pos+needle_size == 6. It's beyond the end offset of row1,
which is begin+value_offsets[0]. So due to the check 'if (pos + needle_size <
begin + value_offsets[i])', we will not set result[i]=1 improperly.
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