dbHasCompleted: Completion status

In DBI: R Database Interface

Description

This method returns if the operation has completed. A SELECT query is completed if all rows have been fetched. A data manipulation statement is always completed.

\Sexpr[results=rd,stage=render]{DBI:::methods_as_rd("dbHasCompleted")}

Usage

dbHasCompleted(res, ...)

Arguments

res	An object inheriting from DBIResult.
...	Other arguments passed on to methods.

Value

dbHasCompleted() returns a logical scalar. For a query initiated by dbSendQuery() with non-empty result set, dbHasCompleted() returns FALSE initially and TRUE after calling dbFetch() without limit. For a query initiated by dbSendStatement(), dbHasCompleted() always returns TRUE.

Failure modes

Attempting to query completion status for a result set cleared with dbClearResult() gives an error.

Specification

The completion status for a query is only guaranteed to be set to FALSE after attempting to fetch past the end of the entire result. Therefore, for a query with an empty result set, the initial return value is unspecified, but the result value is TRUE after trying to fetch only one row.

Similarly, for a query with a result set of length n, the return value is unspecified after fetching n rows, but the result value is TRUE after trying to fetch only one more row.

See Also

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

Examples

con <- dbConnect(RSQLite::SQLite(), ":memory:")

dbWriteTable(con, "mtcars", mtcars)
rs <- dbSendQuery(con, "SELECT * FROM mtcars")

dbHasCompleted(rs)
ret1 <- dbFetch(rs, 10)
dbHasCompleted(rs)
ret2 <- dbFetch(rs)
dbHasCompleted(rs)

dbClearResult(rs)
dbDisconnect(con)

Example output

[1] FALSE
[1] FALSE
[1] TRUE

DBI documentation built on Dec. 20, 2021, 9:07 a.m.