.Dd December 19, 2018
.Dt SQLITE_DBSTATUS_LOOKASIDE_USED 3
.Os
.Sh NAME
.Nm SQLITE_DBSTATUS_LOOKASIDE_USED ,
.Nm SQLITE_DBSTATUS_CACHE_USED ,
.Nm SQLITE_DBSTATUS_SCHEMA_USED ,
.Nm SQLITE_DBSTATUS_STMT_USED ,
.Nm SQLITE_DBSTATUS_LOOKASIDE_HIT ,
.Nm SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE ,
.Nm SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL ,
.Nm SQLITE_DBSTATUS_CACHE_HIT ,
.Nm SQLITE_DBSTATUS_CACHE_MISS ,
.Nm SQLITE_DBSTATUS_CACHE_WRITE ,
.Nm SQLITE_DBSTATUS_DEFERRED_FKS ,
.Nm SQLITE_DBSTATUS_CACHE_USED_SHARED ,
.Nm SQLITE_DBSTATUS_CACHE_SPILL ,
.Nm SQLITE_DBSTATUS_MAX
.Nd Status Parameters for database connections
.Sh SYNOPSIS
.Fd #define SQLITE_DBSTATUS_LOOKASIDE_USED
.Fd #define SQLITE_DBSTATUS_CACHE_USED
.Fd #define SQLITE_DBSTATUS_SCHEMA_USED
.Fd #define SQLITE_DBSTATUS_STMT_USED
.Fd #define SQLITE_DBSTATUS_LOOKASIDE_HIT
.Fd #define SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE
.Fd #define SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL
.Fd #define SQLITE_DBSTATUS_CACHE_HIT
.Fd #define SQLITE_DBSTATUS_CACHE_MISS
.Fd #define SQLITE_DBSTATUS_CACHE_WRITE
.Fd #define SQLITE_DBSTATUS_DEFERRED_FKS
.Fd #define SQLITE_DBSTATUS_CACHE_USED_SHARED
.Fd #define SQLITE_DBSTATUS_CACHE_SPILL
.Fd #define SQLITE_DBSTATUS_MAX
.Sh DESCRIPTION
These constants are the available integer "verbs" that can be passed
as the second argument to the sqlite3_db_status()
interface.
.Pp
New verbs may be added in future releases of SQLite.
Existing verbs might be discontinued.
Applications should check the return code from sqlite3_db_status()
to make sure that the call worked.
The sqlite3_db_status() interface will return a
non-zero error code if a discontinued or unsupported verb is invoked.
.Bl -tag -width Ds
.It SQLITE_DBSTATUS_LOOKASIDE_USED
This parameter returns the number of lookaside memory slots currently
checked out.
.It SQLITE_DBSTATUS_LOOKASIDE_HIT
This parameter returns the number malloc attempts that were satisfied
using lookaside memory.
Only the high-water value is meaningful; the current value is always
zero.
.It SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE
This parameter returns the number malloc attempts that might have been
satisfied using lookaside memory but failed due to the amount of memory
requested being larger than the lookaside slot size.
Only the high-water value is meaningful; the current value is always
zero.
.It SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL
This parameter returns the number malloc attempts that might have been
satisfied using lookaside memory but failed due to all lookaside memory
already being in use.
Only the high-water value is meaningful; the current value is always
zero.
.It SQLITE_DBSTATUS_CACHE_USED
This parameter returns the approximate number of bytes of heap memory
used by all pager caches associated with the database connection.
The highwater mark associated with SQLITE_DBSTATUS_CACHE_USED is always
0.
.It SQLITE_DBSTATUS_CACHE_USED_SHARED
This parameter is similar to DBSTATUS_CACHE_USED, except that if a
pager cache is shared between two or more connections the bytes of
heap memory used by that pager cache is divided evenly between the
attached connections.
In other words, if none of the pager caches associated with the database
connection are shared, this request returns the same value as DBSTATUS_CACHE_USED.
Or, if one or more or the pager caches are shared, the value returned
by this call will be smaller than that returned by DBSTATUS_CACHE_USED.
The highwater mark associated with SQLITE_DBSTATUS_CACHE_USED_SHARED
is always 0.
.It SQLITE_DBSTATUS_SCHEMA_USED
This parameter returns the approximate number of bytes of heap memory
used to store the schema for all databases associated with the connection
- main, temp, and any ATTACH-ed databases.
The full amount of memory used by the schemas is reported, even if
the schema memory is shared with other database connections due to
shared cache mode being enabled.
The highwater mark associated with SQLITE_DBSTATUS_SCHEMA_USED is always
0.
.It SQLITE_DBSTATUS_STMT_USED
This parameter returns the approximate number of bytes of heap and
lookaside memory used by all prepared statements associated with the
database connection.
The highwater mark associated with SQLITE_DBSTATUS_STMT_USED is always
0.
.It SQLITE_DBSTATUS_CACHE_HIT
This parameter returns the number of pager cache hits that have occurred.
The highwater mark associated with SQLITE_DBSTATUS_CACHE_HIT is always
0.
.It SQLITE_DBSTATUS_CACHE_MISS
This parameter returns the number of pager cache misses that have occurred.
The highwater mark associated with SQLITE_DBSTATUS_CACHE_MISS is always
0.
.It SQLITE_DBSTATUS_CACHE_WRITE
This parameter returns the number of dirty cache entries that have
been written to disk.
Specifically, the number of pages written to the wal file in wal mode
databases, or the number of pages written to the database file in rollback
mode databases.
Any pages written as part of transaction rollback or database recovery
operations are not included.
If an IO or other error occurs while writing a page to disk, the effect
on subsequent SQLITE_DBSTATUS_CACHE_WRITE requests is undefined.
The highwater mark associated with SQLITE_DBSTATUS_CACHE_WRITE is always
0.
.It SQLITE_DBSTATUS_CACHE_SPILL
This parameter returns the number of dirty cache entries that have
been written to disk in the middle of a transaction due to the page
cache overflowing.
Transactions are more efficient if they are written to disk all at
once.
When pages spill mid-transaction, that introduces additional overhead.
This parameter can be used help identify inefficiencies that can be
resolve by increasing the cache size.
.It SQLITE_DBSTATUS_DEFERRED_FKS
This parameter returns zero for the current value if and only if all
foreign key constraints (deferred or immediate) have been resolved.
The highwater mark is always 0.
.El
.Pp
.Sh SEE ALSO
.Xr sqlite3_db_status 3