Nicola Crane created ARROW-18266:
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Summary: [R] Make it more obvious how to read in a Parquet file
with a different schema to the inferred one
Key: ARROW-18266
URL: https://issues.apache.org/jira/browse/ARROW-18266
Project: Apache Arrow
Issue Type: Improvement
Components: R
Reporter: Nicola Crane
It's not all that clear from our docs that if we want to read in a Parquet file
and change the schema, we need to call the {{cast()}} method on the Table, e.g.
{code:r}
# Write out data
data <- tibble::tibble(x = c(letters[1:5], NA), y = 1:6)
data_with_schema <- arrow_table(data, schema = schema(x = string(), y =
int64()))
write_parquet(data_with_schema, "data_with_schema.parquet")
# Read in data while specifying a schema
data_in <- read_parquet("data_with_schema.parquet", as_data_frame = FALSE)
data_in$cast(target_schema = schema(x = string(), y = int32()))
{code}
We should document this more clearly. Pehaps we could even update the code here
to automatically do some of this if we pass in a schema to the {...} argument
of {{read_parquet}} _and_ the returned data doesn't match the desired schema?
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