Sun Microsystems 5800 用户手册
field consumes the same number of bytes as the length of the value. A string value consumes
twice as many bytes as the length of the value. These sizes are similar to what is described in the
Sun StorageTek 5800 System Administration Guide, Table 7-6, Number of Bytes Used by Each
Element Type in a Schema Table.
twice as many bytes as the length of the value. These sizes are similar to what is described in the
Sun StorageTek 5800 System Administration Guide, Table 7-6, Number of Bytes Used by Each
Element Type in a Schema Table.
For example, assume dynamic parameter 1 is bound to string
"Hello" in the query
system.test.type_string=?
. The parameter length would then be 12 bytes: 2 bytes overhead
plus 10 bytes for a 5-character string parameter.
Conversely, note that in the query system.test.type_string like ’%Hello%’ that the
parameter is 16 bytes: 2 bytes overhead plus 14 bytes for a 7 character string regardless of the
declared size of the system.test.type_string field in the schema.
parameter is 16 bytes: 2 bytes overhead plus 14 bytes for a 7 character string regardless of the
declared size of the system.test.type_string field in the schema.
For the query system.test.type_date = {date ’2007-01-1’} AND
system.test.type_char=’Hello’
system.test.type_char=’Hello’
, the parameter length is 13 bytes: 2 bytes overhead for each
of two query values plus 4 bytes for a date literal plus 5 bytes for a 5-character char parameter.
Limit the Size of Schema Query Parameters and Literals
When designing a schema, limit the sizes of fields so that planned queries will fit within the size
limits. Most simple queries on a single table will fit within the 8000-byte limit. This is because
the table row definition itself must fit within the similar 8080-bytes for overall table row size.
Also note that complex queries on even a single table (such as queries involving many OR
clauses) may overflow the limit. Schema design and query design must work together carefully
if complex queries are an important part of the application.
limits. Most simple queries on a single table will fit within the 8000-byte limit. This is because
the table row definition itself must fit within the similar 8080-bytes for overall table row size.
Also note that complex queries on even a single table (such as queries involving many OR
clauses) may overflow the limit. Schema design and query design must work together carefully
if complex queries are an important part of the application.
For further information, see
Limit Results Per Fetch
Queries should use a reasonable value of “results per fetch” when a large total result set size is
expected. The maximum result size should not exceed the memory allocated for the query
engine on the server side. If it does, then the query will fail. Dropping the query result size will
allow the query to succeed.
expected. The maximum result size should not exceed the memory allocated for the query
engine on the server side. If it does, then the query will fail. Dropping the query result size will
allow the query to succeed.
If you incorrectly estimate how much memory will be used by the result set, the server will not
fail gracefully with an appropriate error message, but will instead run out of memory.
fail gracefully with an appropriate error message, but will instead run out of memory.
Suggested values are in the 2000-5000 range. Set maxFetchSize = 4098 as an argument to the
query
query
method.
Limit the Size of Schema Query Parameters and Literals
Sun StorageTek 5800 System Client API Reference Manual • June 2008
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