Neoview Query Guide (R2.3, R2.4, R2.5)

Data TypeToken DescriptionToken
textThe access specified: read committed, read uncommitted, stable, skip
conflict, serializable, not specified, or unknown
access_mode
integerEstimate of the number of columns to be returnedcolumns_retrieved
textIndication of whether an optimization for a simple scan operation is used.
The value used is returned if this optimization is used.
fast_scan
textIndication of whether an optimization for returning data from DAM is
used. The value used is returned if this optimization is used.
fast_replydata_move
textPresent only if partition name is specified in the statement. Returns the
name of the partition.
partition_name
expr(text)Columns used as the primary keykey_columns
expr(text)Any predicate expression that is not a key predicate evaluated by the
executor in DAM
executor_predicates
expr(text)Disjunct key predicates used by MDAMmdam_disjunct
expr(text)Predicate expression specified on partitioning key. It is displayed only
if partitioning key differs from clustering key.
part_key_predicate
expr(text)Expression of the begin key predicatebegin_key
expr(text)Expression of the end key predicateend_key
Many details related to the FILE_SCAN operator also apply to the INDEX_SCAN operator. See
the “FILE_SCAN Operator” (page 41).
INDEX_SCAN_UNIQUE Operator
The INDEX_SCAN_UNIQUE operator describes a scan of exactly one row in the index of the
base table.
A unique index scan can be of two types:
• Access to the index structure only (index-only scan).
• Access to the index with a join to the base table.
An index row contains a primary key that includes the indexed columns from the base table.
The index row also includes the primary key of the related row in the base table, which is used
to locate the base table row, if required.
If all of the columns required for the query can be obtained form the index (index-only scan),
then only the INDEX_SCAN_UNIQUE operator will appear in the query plan. Otherwise, the
query plan will show a nested join from the index to the base table, and the base table will be
accessed with the FILE_SCAN_UNIQUE operator using the primary key for the base table row.
The INDEX_SCAN_UNIQUE operator has no child operators. The description field for this
operator contains:
Data TypeToken DescriptionToken
integerA sequential number assigned to the fragment. 0 is always master
executor and 1 is reserved for the Explain plan. Numbers 2 to n will be
ESP or DAM fragments.
fragment_id
integerThe fragment_id for the parent fragment of the current fragment. Value
is (none) for master executor.
parent_frag
textmaster, ESP, or DAMfragment_type
textIndicates whether an optimization for short, simple operations is used.
The value used is returned if this optimization is used.
olt_optimization
44 Query Plan Operators