HuaHuaY commented on code in PR #2461:
URL: https://github.com/apache/orc/pull/2461#discussion_r2610774119
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c++/src/ColumnWriter.cc:
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@@ -1038,6 +1038,8 @@ namespace orc {
if (!useDictionary) {
directLengthEncoder->add(length, numValues, notNull);
+ } else if (dictionary.capacity() < numValues) {
Review Comment:
I think this can solve the expansion overhead at startup at a small cost.
Usually the map does not reserve a large value immediately, but gradually
expands it by a multiple of the size. When the map is very large, calling
reserve to allocate memory for each insertion will take more time, so a
condition is used here to determine.
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