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Message Posted: Tue, 11 Dec 2012 @ 20:25:01 GMT

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Explain collect stats pdcrdata.dbqlogtbl_hst column (UserName)

     1) First, we lock pdcrdata.dbqlogtbl_hst for access.
     2) Next, we do a COLLECT STATISTICS step from pdcrdata.dbqlogtbl_hst
        by way of an all-rows scan into Spool 3 (all_amps), which is built
        locally on the AMPs by using cache during local aggregation.
     3) Then we save the UPDATED STATISTICS from Spool 3 (Last Use) into
        Spool 4, which is built locally on the AMP derived from
        DBC.TVFields by way of the primary index.
     4) We lock DBC.TVFields for write on a RowHash.
     5) We do a single-AMP MERGE DELETE to DBC.TVFields from Spool 4 (Last
        Use) by way of a RowHash match scan.  New updated rows are built
        and the result goes into Spool 5 (one-amp), which is built locally
        on the AMPs.
     6) We do a single-AMP MERGE into DBC.TVFields from Spool 5 (Last Use).
     7) We spoil the parser's dictionary cache for the table.
     8) Finally, we send out an END TRANSACTION step to all AMPs involved
        in processing the request.
     -> No rows are returned to the user as the result of statement 1.

Access lock on the table, Write lock on DBC.TVFields.

Thanks,

Vinay Bagare

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