Stats can have zero UEC when CQD USTAT_ESTIMATE_HBASE_ROW_COUNT is set to 'on'

[QF Chen]

Here are several examples of stats with UEC being 0 (H_DATE, H_D_ID etc). UEC for column h_w_id is reasonable after turning off the CQD and re-update the stats.

>>showstats for table history on every column ;

Histogram data for Table TRAFODION.ORDERENTRY.HISTORY
Table ID: 60287988392838310

   Hist ID # Ints Rowcount UEC Colname(s)
========== ====== =========== =========== ===========================
 964839257 50 1409094 0 H_DATE
 964839251 3 704547 3 H_W_ID
 964839247 10 1409094 0 H_D_ID
 964839240 3 1409094 0 H_C_W_ID
 964839237 10 1409094 0 H_C_D_ID
 964839230 48 1409094 0 H_C_ID
 964839227 1 1409094 0 H_AMOUNT
 964839220 62 1409094 1409094 H_DATA
 964839217 3 1409094 0 "_SALT_"
 964839260 50 1409094 1409094 "_SALT_", H_DATE, H_W_ID, H_D_ID, H_C_W_ID, H_C_D_ID, H_C_ID

[QF Chen (qifan-chen)]

After rebasing to git version 127b8c49e24fe77353d944744299bc10e770c3fc, reinstall hadoop, the original problem was not reproducible any more.

>>showstats for table stock on every column;

Histogram data for Table TRAFODION.ORDERENTRY.STOCK
Table ID: 140790373550268965

   Hist ID # Ints Rowcount UEC Colname(s)
========== ====== =========== =========== ===========================
1506049160 48 200000 200000 S_I_ID
1506049155 1 200000 1 S_W_ID
1506049150 91 200000 91 S_QUANTITY
1506049145 62 200000 200000 S_DIST_01
1506049140 62 200000 200000 S_DIST_02
1506049135 62 200000 200000 S_DIST_03
1506049130 62 200000 200000 S_DIST_04
1506049125 62 200000 200000 S_DIST_05
1506049120 62 200000 200000 S_DIST_06
1506049115 62 200000 200000 S_DIST_07
1506049110 62 200000 200000 S_DIST_08
1506049105 62 200000 200000 S_DIST_09
1506049100 62 200000 200000 S_DIST
1506049095 1 200000 1 S_YTD
1506049090 1 200000 1 S_ORDER_CNT
1506049085 1 200000 1 S_REMOTE_CNT
1506049080 62 200000 200000 S_DATA
1506049075 1 200000 1 "_SALT_"
1506049165 50 200000 200000 "_SALT_", S_W_ID, S_I_ID

>>showstats for table neworder on every column;

Histogram data for Table TRAFODION.ORDERENTRY.NEWORDER
Table ID: 140790373550268398

   Hist ID # Ints Rowcount UEC Colname(s)
========== ====== =========== =========== ===========================
1511505062 48 900 900 NO_O_ID
1511505057 1 900 1 NO_D_ID
1511505052 1 900 1 NO_W_ID
1511505047 1 900 1 "_SALT_"
1511505067 50 900 900 "_SALT_", NO_W_ID, NO_D_ID, NO_O_ID

[QF Chen (qifan-chen)]

On subsequent runs, UECs were all zero.

The size of the hadoop data file (say, for stock table) at the time of update stats is reasonable.

-rwxrwxrwx 1 qchen supergroup 189861644 2014-12-11 00:30 /hbase/data/default/TRAFODION.ORDERENTRY.STOCK/45b88110addf485272cf281521e16de6/#1/20d7c469a0c94be89a44e7229b923961_SeqId_2_
-rwxrwxrwx 1 qchen supergroup 189861644 2014-12-11 00:53 /hbase/data/default/TRAFODION.ORDERENTRY.STOCK/45b88110addf485272cf281521e16de6/#1/5d30c9f337dd406e8c4f06f9e18a8194_SeqId_4_
-rwxrwxrwx 1 qchen supergroup 189861644 2014-12-11 00:46 /hbase/data/default/TRAFODION.ORDERENTRY.STOCK/45b88110addf485272cf281521e16de6/#1/d1596672ded1492292c838c7ac8ecaa1_SeqId_3_
-rwxr-xr-x 3 qchen supergroup 83 2014-12-11 00:27 /hbase/data/default/TRAFODION.ORDERENTRY.STOCK/45b88110addf485272cf281521e16de6/.regioninfo
-rwxr-xr-x 3 qchen supergroup 83 2014-12-11 00:27 /hbase/data/default/TRAFODION.ORDERENTRY.STOCK/a4e2ea1d0d510248fc2b9b19c658bd12/.regioninfo
-rwxr-xr-x 3 qchen supergroup 83 2014-12-11 00:27 /hbase/data/default/TRAFODION.ORDERENTRY.STOCK/b32f2297781258c6ddf2e46048e3de25/.regioninfo
-rwxr-xr-x 3 qchen supergroup 71 2014-12-11 00:27 /hbase/data/default/TRAFODION.ORDERENTRY.STOCK/ee51d72ad992eec3037e32ab4249421f/.regioninfo