spec_meta_bind: spec_meta_bind

In DBItest: Testing DBI Backends

spec_meta_bind

Description

spec_meta_bind

spec_meta_bind

spec_meta_bind

Value

dbBind() returns the result set, invisibly, for queries issued by dbSendQuery() or dbSendQueryArrow() and also for data manipulation statements issued by dbSendStatement().

Specification

DBI clients execute parametrized statements as follows:

1. Call dbSendQuery(), dbSendQueryArrow() or dbSendStatement() with a query or statement that contains placeholders, store the returned DBIResult object in a variable. Mixing placeholders (in particular, named and unnamed ones) is not recommended. It is good practice to register a call to dbClearResult() via on.exit() right after calling dbSendQuery() or dbSendStatement() (see the last enumeration item). Until dbBind() or dbBindArrow() have been called, the returned result set object has the following behavior:

   • dbFetch() raises an error (for dbSendQuery() and dbSendQueryArrow())

   • dbGetRowCount() returns zero (for dbSendQuery() and dbSendQueryArrow())

   • dbGetRowsAffected() returns an integer NA (for dbSendStatement())

   • dbIsValid() returns TRUE

   • dbHasCompleted() returns FALSE

2. Call dbBind() or dbBindArrow():

   • For dbBind(), the params argument must be a list where all elements have the same lengths and contain values supported by the backend. A data.frame is internally stored as such a list.

   • For dbBindArrow(), the params argument must be a nanoarrow array stream, with one column per query parameter.

3. Retrieve the data or the number of affected rows from the DBIResult object.

   • For queries issued by dbSendQuery() or dbSendQueryArrow(), call dbFetch().

   • For statements issued by dbSendStatements(), call dbGetRowsAffected(). (Execution begins immediately after the dbBind() call, the statement is processed entirely before the function returns.)

4. Repeat 2. and 3. as necessary.

5. Close the result set via dbClearResult().

The elements of the params argument do not need to be scalars, vectors of arbitrary length (including length 0) are supported. For queries, calling dbFetch() binding such parameters returns concatenated results, equivalent to binding and fetching for each set of values and connecting via rbind(). For data manipulation statements, dbGetRowsAffected() returns the total number of rows affected if binding non-scalar parameters. dbBind() also accepts repeated calls on the same result set for both queries and data manipulation statements, even if no results are fetched between calls to dbBind(), for both queries and data manipulation statements.

If the placeholders in the query are named, their order in the params argument is not important.

At least the following data types are accepted on input (including NA):

• integer

• numeric

• logical for Boolean values

• character (also with special characters such as spaces, newlines, quotes, and backslashes)

• factor (bound as character, with warning)

• Date (also when stored internally as integer)

• POSIXct timestamps

• POSIXlt timestamps

• difftime values (also with units other than seconds and with the value stored as integer)

• lists of raw for blobs (with NULL entries for SQL NULL values)

• objects of type blob::blob

Failure modes

Calling dbBind() for a query without parameters raises an error.

Binding too many or not enough values, or parameters with wrong names or unequal length, also raises an error. If the placeholders in the query are named, all parameter values must have names (which must not be empty or NA), and vice versa, otherwise an error is raised. The behavior for mixing placeholders of different types (in particular mixing positional and named placeholders) is not specified.

Calling dbBind() on a result set already cleared by dbClearResult() also raises an error.

See Also

Other meta specifications: spec_get_info, spec_meta_column_info, spec_meta_get_row_count, spec_meta_get_rows_affected, spec_meta_get_statement, spec_meta_has_completed, spec_meta_is_valid

Other meta specifications: spec_get_info, spec_meta_column_info, spec_meta_get_row_count, spec_meta_get_rows_affected, spec_meta_get_statement, spec_meta_has_completed, spec_meta_is_valid

Other meta specifications: spec_get_info, spec_meta_column_info, spec_meta_get_row_count, spec_meta_get_rows_affected, spec_meta_get_statement, spec_meta_has_completed, spec_meta_is_valid

DBItest documentation built on June 22, 2024, 11:55 a.m.