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https://issues.apache.org/jira/browse/ARROW-16578?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17536955#comment-17536955
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Hideaki Hayashi commented on ARROW-16578:
-----------------------------------------
is.na() also has the same kind of performance issue.
{{df1 <- tibble::tibble(x=as.character(floor(runif(1000000) * 20)))}}
{{write_parquet(df1,"/tmp/test.parquet")}}
{{df2 <- read_parquet("/tmp/test.parquet")}}
{{system.time(is.na(df1$x))}}
{{# user system elapsed }}
{{# 0.003 0.000 0.003}}
{{system.time(is.na(df2$x))}}
{{# user system elapsed }}
{{# 0.878 0.079 0.957 }}
> [R] unique() on a column of a tibble is much slower after writing to and
> reading from a parquet file
> ----------------------------------------------------------------------------------------------------
>
> Key: ARROW-16578
> URL: https://issues.apache.org/jira/browse/ARROW-16578
> Project: Apache Arrow
> Issue Type: Bug
> Components: Parquet, R
> Affects Versions: 7.0.0, 8.0.0
> Reporter: Hideaki Hayashi
> Priority: Major
>
> unique() on a column of a tibble is much slower after writing to and reading
> from a parquet file.
> Here is a reprex.
> {{df1 <- tibble::tibble(x=as.character(floor(runif(1000000) * 20)))}}
> {{write_parquet(df1,"/tmp/test.parquet")}}
> {{df2 <- read_parquet("/tmp/test.parquet")}}
> {{system.time(unique(df1$x))}}
> {{# Result on my late 2020 macbook pro with M1 processor:}}
> {{# user system elapsed }}
> {{# 0.020 0.000 0.021 }}
> {{system.time(unique(df2$x))}}
> {{# user system elapsed }}
> {{# 5.230 0.419 5.649 }}
>
>
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