Is this DBMS object still valid?
This generic tests whether a database object is still valid (i.e. it hasn't been disconnected or cleared).
dbIsValid(dbObj, ...)
dbObj |
An object inheriting from DBIObject, i.e. DBIDriver, DBIConnection, or a DBIResult |
... |
Other arguments to methods. |
dbIsValid()
returns a logical scalar,
TRUE
if the object specified by dbObj
is valid,
FALSE
otherwise.
A DBIConnection object is initially valid,
and becomes invalid after disconnecting with dbDisconnect()
.
For an invalid connection object (e.g., for some drivers if the object
is saved to a file and then restored), the method also returns FALSE
.
A DBIResult object is valid after a call to dbSendQuery()
,
and stays valid even after all rows have been fetched;
only clearing it with dbClearResult()
invalidates it.
A DBIResult object is also valid after a call to dbSendStatement()
,
and stays valid after querying the number of rows affected;
only clearing it with dbClearResult()
invalidates it.
If the connection to the database system is dropped (e.g., due to
connectivity problems, server failure, etc.), dbIsValid()
should return
FALSE
. This is not tested automatically.
Other DBIDriver generics:
DBIDriver-class
,
dbCanConnect()
,
dbConnect()
,
dbDataType()
,
dbDriver()
,
dbGetInfo()
,
dbIsReadOnly()
,
dbListConnections()
Other DBIConnection generics:
DBIConnection-class
,
dbAppendTable()
,
dbCreateTable()
,
dbDataType()
,
dbDisconnect()
,
dbExecute()
,
dbExistsTable()
,
dbGetException()
,
dbGetInfo()
,
dbGetQuery()
,
dbIsReadOnly()
,
dbListFields()
,
dbListObjects()
,
dbListResults()
,
dbListTables()
,
dbReadTable()
,
dbRemoveTable()
,
dbSendQuery()
,
dbSendStatement()
,
dbWriteTable()
Other DBIResult generics:
DBIResult-class
,
dbBind()
,
dbClearResult()
,
dbColumnInfo()
,
dbFetch()
,
dbGetInfo()
,
dbGetRowCount()
,
dbGetRowsAffected()
,
dbGetStatement()
,
dbHasCompleted()
,
dbIsReadOnly()
,
dbQuoteIdentifier()
,
dbQuoteLiteral()
,
dbQuoteString()
,
dbUnquoteIdentifier()
dbIsValid(RSQLite::SQLite()) con <- dbConnect(RSQLite::SQLite(), ":memory:") dbIsValid(con) rs <- dbSendQuery(con, "SELECT 1") dbIsValid(rs) dbClearResult(rs) dbIsValid(rs) dbDisconnect(con) dbIsValid(con)
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