HappenLee commented on code in PR #63498:
URL: https://github.com/apache/doris/pull/63498#discussion_r3285142379
##########
be/src/core/column/predicate_column.h:
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@@ -293,6 +293,41 @@ class PredicateColumnType final : public
COWHelper<IColumn, PredicateColumnType<
}
}
+ // Insert `num` entries with only length information (no actual char data).
+ // The chars buffer is zero-filled so that filter_by_selector can safely
+ // memcpy without reading meaningful content. Used in OFFSET_ONLY reading
+ // mode where only string lengths (for length() function) are needed.
+ void insert_offsets_from_lengths(const uint32_t* lengths, size_t num)
override {
+ if constexpr (std::is_same_v<T, StringRef>) {
+ if (UNLIKELY(num == 0)) {
+ return;
+ }
+ size_t total_bytes = 0;
+ for (size_t i = 0; i < num; ++i) {
+ total_bytes += lengths[i];
+ }
+ // Allocate and zero-fill a single backing buffer so that each
StringRef
+ // points to valid (though meaningless) memory. filter_by_selector
will
+ // memcpy from these pointers, so they must not be null for
non-zero lengths.
+ char* buf = total_bytes > 0 ? _arena.alloc(total_bytes) : nullptr;
+ if (total_bytes > 0) {
+ memset(buf, 0, total_bytes);
+ }
+ size_t org_elem_num = data.size();
+ data.resize(org_elem_num + num);
+ size_t offset = 0;
+ for (size_t i = 0; i < num; ++i) {
+ // For zero-length strings, data pointer is null;
insert_many_strings
+ // and filter_by_selector both guard on size > 0 before
dereferencing.
+ data[org_elem_num + i].data = (lengths[i] > 0) ? (buf +
offset) : nullptr;
Review Comment:
这里是没问题的，因为insert default就是这个行为
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