bdFrame
or
bdVector
object,
including the files used for storing the data, and their sizes.
This function requires the bigdata library section to be loaded.
bd.object.info(obj)
bdVector
or
bdFrame
, an error is generated.
valid
:
This is
TRUE
if
obj
is a valid big data object.
If this is
FALSE
, the rest of the elements of this list are
NULL
.
columnNum
:
A
bdVector
is actually represented as a column within a
bdFrame
.
If
obj
is a
bdVector
,
this element is the column number of this
bdVector
,
and the elements below such as
frameRowBytes
contain information
about the
bdFrame
containing this
bdVector
.
If
obj
is not a
bdVector
, this element is
NULL
.
columnElements
:
If
obj
is a
bdVector
,
this is the number of elements in the vector.
This should be the same as the
frameRows
value.
If
obj
is not a
bdVector
, this element is
NULL
.
columnElementBytes
:
If
obj
is a
bdVector
,
this is the number of bytes used to represent each element in the vector.
If
obj
is not a
bdVector
, this element is
NULL
.
columnTotalBytes
:
If
obj
is a
bdVector
,
this is the total number of bytes used to represent the data in this vector.
If
obj
is not a
bdVector
, this element is
NULL
.
frameRows
:
The number of rows in the
bdFrame
.
frameColumns
:
The number of columns in the
bdFrame
.
frameRowBytes
:
The number of bytes used to represent each row in the
bdFrame
.
frameTotalBytes
:
The total number of bytes used to represent the data in the
bdFrame
.
cacheDir
:
The directory containing the files representing this object.
dataFile
:
The file name of the file containing the data values for this object.
dataFileExists
:
This is
TRUE
if the data file exists.
dataFileBytes
:
The size in bytes of the data file.
metaFile
:
The file name of the file containing the meta-data for this object.
metaFileExists
:
This is
TRUE
if the meta-data file exists.
metaFileBytes
:
The size in bytes of the meta-data file.
blobFile
:
The file name of a file used for representing variable-length "blob" data
associated with the object.
This file is normally empty, except in a few special cases.
blobFileExists
:
This is
TRUE
if the blob file exists.
blobFileBytes
:
The size in bytes of the blob file.
This function extracts information about the internal files used to represent
a
bdFrame
or
bdVector
, such as the file names and sizes.
If the performance of a big data operation seems too slow,
it may be helpful to examine the size of the data files.
This function exposes the fact that a
bdVector
is actually represented as a column in a
bdFrame
.
If the underlying
bdFrame
has many columns,
manipulating the
bdVector
may involve reading
the entire
bdFrame
data file.
In some cases, it may be more efficient to copy the vector data
out of a larger
bdFrame
, before manipulating it.
For example, rather than selecting a
bdVector
with the expression
mybdframe[[1]]
, which creates a
bdVector
referencing the original
myframe
,
one could do
bd.select.rows(mybdframe,columns=1)[[1]]
,
which first copies the column into a one-column
bdFrame
before extracting the column
bdVector
for the column.
bd.object.info(as.bdFrame(fuel.frame))