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Fix the example in documentation for get_dremel_data() #17242

17 changes: 9 additions & 8 deletions cpp/include/cudf/lists/detail/dremel.hpp
Original file line number Diff line number Diff line change
Expand Up @@ -58,7 +58,7 @@ struct dremel_data {
};

/**
* @brief Get the dremel offsets and repetition and definition levels for a LIST column
* @brief Get the dremel offsets, and repetition and definition levels for a LIST column
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*
* Dremel is a query system created by Google for ad hoc data analysis. The Dremel engine is
* described in depth in the paper "Dremel: Interactive Analysis of Web-Scale
Expand All @@ -74,7 +74,7 @@ struct dremel_data {
*
* http://www.goldsborough.me/distributed-systems/2019/05/18/21-09-00-a_look_at_dremel/
* https://akshays-blog.medium.com/wrapping-head-around-repetition-and-definition-levels-in-dremel-powering-bigquery-c1a33c9695da
* https://blog.twitter.com/engineering/en_us/a/2013/dremel-made-simple-with-parquet
* https://blog.x.com/engineering/en_us/a/2013/dremel-made-simple-with-parquet
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*
* The remainder of this documentation assumes familiarity with the Dremel concepts.
*
Expand Down Expand Up @@ -102,16 +102,17 @@ struct dremel_data {
* ```
* We can represent it in cudf format with two level of offsets like this:
* ```
* Level 0 offsets = {0, 0, 3, 5, 6}
* Level 0 offsets = {0, 0, 3, 4}
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* Level 1 offsets = {0, 0, 3, 5, 5}
* Values = {1, 2, 3, 4, 5}
* ```
* The desired result of this function is the repetition and definition level values that
* correspond to the data values:
* The desired result of this function is the dremel offsets, and repetition and definition level
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* values that correspond to the data values:
* ```
* col = {[], [[], [1, 2, 3], [4, 5]], [[]]}
* def = { 0 1, 2, 2, 2, 2, 2, 1 }
* rep = { 0, 0, 0, 2, 2, 1, 2, 0 }
* col = {[], [[], [1, 2, 3], [4, 5]], [[]]}
* dremel_offsets = { 0, 1, 7, 8}
* def_levels = { 0 1, 2, 2, 2, 2, 2, 1 }
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* rep_levels = { 0, 0, 1, 2, 2, 1, 2, 0 }
* ```
*
* Since repetition and definition levels arrays contain a value for each empty list, the size of
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@mhaseeb123 mhaseeb123 Nov 5, 2024

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Reviewers: Would love an extra set of eyes at the explanation of the algorithm at L120-151 if you could. I looked into it while making the edits and the explanation looked fine to me so I didn't make any changes. Thanks!

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Looks good, I'm just confused as to why we included the algorithm description in the public header :)
Not a concern for this PR

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