Neoview SQL Reference Manual (R2.5)

The operator typeOPERATOR
Query optimizations that were appliedOPT
Additional information about the operatorDESCRIPTION
Estimated number of rows returned by the plan. CARDINALITY and
ROWS_OUT are the same.
CARD
This example uses OPTIONS 'f ':
>>explain options 'f' select * from region;
LC RC OP OPERATOR OPT DESCRIPTION CARD
--- --- --- -------------------- -------- -------------------- ---------
2 . 3 root 1.00E+002
1 . 2 partition_access 1.00E+002
. . 1 file_scan fs fr REGION 1.00E+002
--- SQL operation complete.
To use the EXPLAIN statement with a prepared statement, first prepare the query. Then use the
EXPLAIN statement:
PREPARE q FROM SELECT * FROM REGION;
EXPLAIN options 'f' q;
The FILE_SCAN operator is the only operator in this example that shows additional information
in the OPT and DESCRIPTION fields. 'fs' indicates that fast-scan optimization was used. 'fr'
indicates that fast-reply data-move optimization was used. The table name is shown in the
DESCRIPTION field. For information about these special optimization techniques, see the listing
of each operator in the Neoview Query Guide.
Normal User [OPTIONS 'n'] Considerations
The normal user option provides more information about the query plan than OPTIONS 'f'.
OPTIONS 'n' is the default option, so you can simply execute EXPLAIN query-text without
specifying OPTIONS 'n'.
OPTIONS 'n' provides two digits of precision for floating-point cost values.
OPTIONS 'n' provides a plan summary as well as values of the fields for the operators in the
query execution plan. Table 2-4 describes the plan summary.
Table 2-4 Plan Summary Information
Shows DYNAMICALLY COMPILED when a query statement or prepared
statement is supplied as the argument to the EXPLAIN statement.
MODULE_NAME
Name of the prepared statement. For example, in the prepared statement
PREPARE newstmt from SELECT * FROM T, the
STATEMENT_NAME field value is NEWSTMT.
STATEMENT_NAME
An identifier generated by the database.PLAN_ID
Estimated number of rows returned by the plan.ROWS_OUT
Estimated total cost of the plan.EST_TOTAL_COST
SQL query being explained in this query plan.STATEMENT
The EXPLAIN plan output provides the following information, as applicable, for each operator
of the query execution plan. The "NODE LISTING" heading means a list of the plan's operators
will follow.
126 SQL Statements