DBI (version 1.2.2)

dbIsValid: Is this DBMS object still valid?

Description

This generic tests whether a database object is still valid (i.e. it hasn't been disconnected or cleared).

DBI:::methods_as_rd("dbIsValid")

Usage

dbIsValid(dbObj, ...)

Value

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.

Arguments

dbObj

An object inheriting from DBIObject, i.e. DBIDriver, DBIConnection, or a DBIResult

...

Other arguments to methods.

See Also

Other DBIDriver generics: DBIDriver-class, dbCanConnect(), dbConnect(), dbDataType(), dbDriver(), dbGetInfo(), dbIsReadOnly(), dbListConnections()

Other DBIConnection generics: DBIConnection-class, dbAppendTable(), dbAppendTableArrow(), dbCreateTable(), dbCreateTableArrow(), dbDataType(), dbDisconnect(), dbExecute(), dbExistsTable(), dbGetException(), dbGetInfo(), dbGetQuery(), dbGetQueryArrow(), dbIsReadOnly(), dbListFields(), dbListObjects(), dbListResults(), dbListTables(), dbQuoteIdentifier(), dbReadTable(), dbReadTableArrow(), dbRemoveTable(), dbSendQuery(), dbSendQueryArrow(), dbSendStatement(), dbUnquoteIdentifier(), dbWriteTable(), dbWriteTableArrow()

Other DBIResult generics: DBIResult-class, dbBind(), dbClearResult(), dbColumnInfo(), dbFetch(), dbGetInfo(), dbGetRowCount(), dbGetRowsAffected(), dbGetStatement(), dbHasCompleted(), dbIsReadOnly(), dbQuoteLiteral(), dbQuoteString()

Other DBIResultArrow generics: DBIResultArrow-class, dbBind(), dbClearResult(), dbFetchArrow(), dbFetchArrowChunk(), dbHasCompleted()

Examples

if (FALSE) { # requireNamespace("RSQLite", quietly = TRUE)
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)
}