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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