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SYSTEM.HASH contains an entry for each hash structure
you create.
This view is initially empty, but is updated whenever ALLBASE/SQL
processes a hash-related CREATE TABLE, DROP TABLE, TRANSFER
OWNERSHIP, or UPDATE STATISTICS statement. Table 8-15 System.Hash | Column Name | Type | Length | DESCRIPTION |
|---|
| TABLENAME | CHAR | 20 | Name of the table on which the hash is defined | | OWNER | CHAR | 20 | Owner of the table on which the hash structure is defined | | NUMC | INTEGER | 4 | Number of columns in the hash key | | COLNUMS | BINARY | 32 | A vector of 16 SYSTEM.COLUMN entries, each of type SMALLINT, identifying
the column numbers the hash is defined over. In ISQL, each SMALLINT (two-byte) entry is
displayed as a field of 4 hexadecimal digits. | | PRIMPAGES | INTEGER | 4 | Number of primary pages allocated for the hash structure | | NPPAGES | INTEGER | 4 | Number of primary pages in use, excluding page table pages | | AVGLEN | FLOAT | 8 | Average chain length | | MAXLEN | INTEGER | 4 | Maximum chain length | | NFULL | INTEGER | 4 | Number of primary pages that are more than half full | | NOVERFLOW | INTEGER | 4 | Number of primary pages with overflow pages | | UNIQUE | SMALLINT | 2 | Uniqueness indicator; currently always 1 |
EXAMPLE | |
SELECT * FROM System.Hash;
+--------------------+--------------------+-----------
|TABLENAME |OWNER |NUMC
+--------------------+--------------------+-----------
|VENDORS |PURCHDB | 1
-------------------------------------------------------
Number of rows selected is 1
U[p], d[own], l[eft], r[ight], t[op], b[ottom], pr[int] <n>,or e[nd]> r
+----------------------------------------------------------------
|COLNUMS
+----------------------------------------------------------------
|0001000000000000000000000000000000000000000000000000000000000000
+----------------------------------------------------------------
Number of rows selected is 1
U[p], d[own], l[eft], r[ight], t[op], b[ottom], pr[int] <n>,or e[nd]> r
+-----------+-----------+----------------+---------
|PRIMPAGES |NPPAGES |AVGLEN |MAXLEN
+-----------+-----------+----------------+---------
| 10| 18| 1.00| 1
---------------------------------------------------------------------------
Number of rows selected is 1
U[p], d[own], l[eft], r[ight], t[op], b[ottom], pr[int] <n>,or e[nd]> r
+-----------+-----------+------
|NFULL NOVERFLOW UNIQUE
+-----------+-----------+------
| 0| 0| 1
------------------------------------------------------------------------
Number of rows selected is 1
U[p], d[own], l[eft], r[ight], t[op], b[ottom], pr[int] <n>,or e[nd]> e
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