[HIVE-9840] select count(*) <tablename> should give exception

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 0.14.0
• Component/s: Hive, Parser, Query Planning, Query Processor

Environment

hive 0.14

• Assignee: Unassigned
• Reporter: Pradeep Bhadani
• Created: 03/Mar/15 16:39
• Updated: 04/Mar/15 22:14

Description

When I am running hive query [count (*)] with any table name or without table name , It spawn MR job and return result as "1"
These all command (as below) should fail with Syntax Error

hive > select count ( * ) <any-table-name>
hive > select count ( * ) <non-existing-table-name>
hive > select count ( * ) <existing-table-name>
hive > select count ( * )

When we provide any table name or do not supllie any argument , it spawn mapreduce job to count the row of table name "_dummy_table".

EXPLAIN of above commands :

—
hive> EXPLAIN select count( * ) sample;
OK
STAGE DEPENDENCIES:
Stage-1 is a root stage
Stage-0 depends on stages: Stage-1

STAGE PLANS:
Stage: Stage-1
Map Reduce
Map Operator Tree:
TableScan
alias: _dummy_table
Row Limit Per Split: 1
Statistics: Num rows: 0 Data size: 1 Basic stats: PARTIAL Column stats: COMPLETE
Select Operator
Statistics: Num rows: 0 Data size: 1 Basic stats: PARTIAL Column stats: COMPLETE
Group By Operator
aggregations: count()
mode: hash
outputColumnNames: _col0
Statistics: Num rows: 1 Data size: 8 Basic stats: COMPLETE Column stats: COMPLETE
Reduce Output Operator
sort order:
Statistics: Num rows: 1 Data size: 8 Basic stats: COMPLETE Column stats: COMPLETE
value expressions: _col0 (type: bigint)
Reduce Operator Tree:
Group By Operator
aggregations: count(VALUE._col0)
mode: mergepartial
outputColumnNames: _col0
Statistics: Num rows: 1 Data size: 8 Basic stats: COMPLETE Column stats: COMPLETE
Select Operator
expressions: _col0 (type: bigint)
outputColumnNames: _col0
Statistics: Num rows: 1 Data size: 8 Basic stats: COMPLETE Column stats: COMPLETE
File Output Operator
compressed: false
Statistics: Num rows: 1 Data size: 8 Basic stats: COMPLETE Column stats: COMPLETE
table:
input format: org.apache.hadoop.mapred.TextInputFormat
output format: org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat
serde: org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe

Stage: Stage-0
Fetch Operator
limit: -1
Processor Tree:
ListSink

Time taken: 0.071 seconds, Fetched: 47 row(s)
—

NOTE: Table "sample" do not exist in my hive.

Issue Links

• is related to: HIVE-1558 introducing the "dual" table
• is related to: HIVE-6617 Reduce ambiguity in grammar