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https://issues.apache.org/jira/browse/HIVE-21924?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Prasanth Jayachandran updated HIVE-21924:
-----------------------------------------
Description:
https://github.com/apache/hive/blob/967a1cc98beede8e6568ce750ebeb6e0d048b8ea/ql/src/java/org/apache/hadoop/hive/ql/io/HiveInputFormat.java#L494-L503
{code}
int headerCount = 0;
int footerCount = 0;
if (table != null) {
headerCount = Utilities.getHeaderCount(table);
footerCount = Utilities.getFooterCount(table, conf);
if (headerCount != 0 || footerCount != 0) {
// Input file has header or footer, cannot be splitted.
HiveConf.setLongVar(conf, ConfVars.MAPREDMINSPLITSIZE, Long.MAX_VALUE);
}
}
{code}
this piece of code makes the CSV (or any text files with header/footer) files
not splittable if header or footer is present.
If only header is present, we can find the offset after first line break and
use that to split. Similarly for footer, may be read few KB's of data at the
end and find the last line break offset. Use that to determine the data range
which can be used for splitting. Few reads during split generation are cheaper
than not splitting the file at all.
was:
https://github.com/apache/hive/blob/967a1cc98beede8e6568ce750ebeb6e0d048b8ea/ql/src/java/org/apache/hadoop/hive/ql/io/HiveInputFormat.java#L494-L503
this piece of code makes the CSV (or any text files with header/footer) files
not splittable if header or footer is present.
If only header is present, we can find the offset after first line break and
use that to split. Similarly for footer, may be read few KB's of data at the
end and find the last line break offset. Use that to determine the data range
which can be used for splitting. Few reads during split generation are cheaper
than not splitting the file at all.
> Split text files if only header/footer is present
> -------------------------------------------------
>
> Key: HIVE-21924
> URL: https://issues.apache.org/jira/browse/HIVE-21924
> Project: Hive
> Issue Type: Improvement
> Components: File Formats
> Affects Versions: 2.4.0, 4.0.0, 3.2.0
> Reporter: Prasanth Jayachandran
> Priority: Major
>
> https://github.com/apache/hive/blob/967a1cc98beede8e6568ce750ebeb6e0d048b8ea/ql/src/java/org/apache/hadoop/hive/ql/io/HiveInputFormat.java#L494-L503
>
> {code}
> int headerCount = 0;
> int footerCount = 0;
> if (table != null) {
> headerCount = Utilities.getHeaderCount(table);
> footerCount = Utilities.getFooterCount(table, conf);
> if (headerCount != 0 || footerCount != 0) {
> // Input file has header or footer, cannot be splitted.
> HiveConf.setLongVar(conf, ConfVars.MAPREDMINSPLITSIZE,
> Long.MAX_VALUE);
> }
> }
> {code}
> this piece of code makes the CSV (or any text files with header/footer) files
> not splittable if header or footer is present.
> If only header is present, we can find the offset after first line break and
> use that to split. Similarly for footer, may be read few KB's of data at the
> end and find the last line break offset. Use that to determine the data range
> which can be used for splitting. Few reads during split generation are
> cheaper than not splitting the file at all.
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