[PARQUET-2120] parquet-cli dictionary command fails on pages without dictionary encoding

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.12.2
• Fix Version/s: 1.12.3
• Component/s: parquet-cli
• Assignee: Unassigned
• Reporter: Willi Raschkowski
• Created: 12/Feb/22 15:00
• Updated: 21/Jun/22 11:13
• Resolved: 21/Jun/22 11:13

Description

parquet-cli's dictionary command fails with an NPE if a page does not have dictionary encoding:

$ parquet dictionary --column col a-b-c.snappy.parquet                
Unknown error
java.lang.NullPointerException: Cannot invoke "org.apache.parquet.column.page.DictionaryPage.getEncoding()" because "page" is null
	at org.apache.parquet.cli.commands.ShowDictionaryCommand.run(ShowDictionaryCommand.java:78)
	at org.apache.parquet.cli.Main.run(Main.java:155)
	at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:76)
	at org.apache.parquet.cli.Main.main(Main.java:185)

$ parquet meta a-b-c.snappy.parquet      
...
Row group 0:  count: 1  46.00 B records  start: 4  total: 46 B
--------------------------------------------------------------------------------
     type      encodings count     avg size   nulls   min / max
col  BINARY    S   _     1         46.00 B    0       "a" / "a"

Row group 1:  count: 200  0.34 B records  start: 50  total: 69 B
--------------------------------------------------------------------------------
     type      encodings count     avg size   nulls   min / max
col  BINARY    S _ R     200       0.34 B     0       "b" / "c"

(Note the missing R / dictionary encoding on that first page.)

Someone familiar with Parquet might guess from the NPE that there's no dictionary encoding. But for files that mix pages with and without dictionary encoding (like above), the command will fail before getting to pages that actually have dictionaries.

The problem is that this line assumes readDictionaryPage always returns a page and doesn't handle when it does not, i.e. when it returns null.

Issue Links

• is depended upon by: PARQUET-2145 Release 1.12.3