OPTIONS¶
- ifmt=<in-format>
Specifies the format of the input table as specified by
parameter
in. The known formats are listed in SUN/256. This flag can be
used if you know what format your table is in. If it has the special value
(auto) (the default), then an attempt will be made to detect the format
of the table automatically. This cannot always be done correctly however, in
which case the program will exit with an error explaining which formats were
attempted. This parameter is ignored for scheme-specified tables.
- istream=true|false
If set true, the input table specified by the
in
parameter will be read as a stream. It is necessary to give the
ifmt
parameter in this case. Depending on the required operations and processing
mode, this may cause the read to fail (sometimes it is necessary to read the
table more than once). It is not normally necessary to set this flag; in most
cases the data will be streamed automatically if that is the best thing to do.
However it can sometimes result in less resource usage when processing large
files in certain formats (such as VOTable). This parameter is ignored for
scheme-specified tables.
- in=<table>
The location of the input table. This may take one of the
following forms:
- A filename.
- A URL.
- The special value "-", meaning standard input. In this
case the input format must be given explicitly using the ifmt
parameter. Note that not all formats can be streamed in this way.
- A scheme specification of the form
:<scheme-name>:<scheme-args>.
- A system command line with either a "<" character at
the start, or a "|" character at the end
("<syscmd" or "syscmd|"). This
executes the given pipeline and reads from its standard output. This will
probably only work on unix-like systems.
In any case, compressed data in one of the supported compression formats (gzip,
Unix compress or bzip2) will be decompressed transparently.
- icmd=<cmds>
Specifies processing to be performed on the input table
as specified by parameter
in, before any other processing has taken
place. The value of this parameter is one or more of the filter commands
described in SUN/256. If more than one is given, they must be separated by
semicolon characters (";"). This parameter can be repeated multiple
times on the same command line to build up a list of processing steps. The
sequence of commands given in this way defines the processing pipeline which
is performed on the table.
Commands may alteratively be supplied in an external file, by
using the indirection character '@'. Thus a value of
"@filename" causes the file filename to be read for
a list of filter commands to execute. The commands in the file may be
separated by newline characters and/or semicolons, and lines which are blank
or which start with a '#' character are ignored.
- ocmd=<cmds>
Specifies processing to be performed on the output table,
after all other processing has taken place. The value of this parameter is one
or more of the filter commands described in SUN/256. If more than one is
given, they must be separated by semicolon characters (";"). This
parameter can be repeated multiple times on the same command line to build up
a list of processing steps. The sequence of commands given in this way defines
the processing pipeline which is performed on the table.
Commands may alteratively be supplied in an external file, by
using the indirection character '@'. Thus a value of
"@filename" causes the file filename to be read for
a list of filter commands to execute. The commands in the file may be
separated by newline characters and/or semicolons, and lines which are blank
or which start with a '#' character are ignored.
- omode=out|meta|stats|count|checksum|cgi|discard|topcat|samp|tosql|gui
The mode in which the result table will be output. The
default mode is
out, which means that the result will be written as a
new table to disk or elsewhere, as determined by the
out and
ofmt parameters. However, there are other possibilities, which
correspond to uses to which a table can be put other than outputting it, such
as displaying metadata, calculating statistics, or populating a table in an
SQL database. For some values of this parameter, additional parameters
(
<mode-args>) are required to determine the exact behaviour.
Possible values are
- out
- meta
- stats
- count
- checksum
- cgi
- discard
- topcat
- samp
- tosql
- gui
Use the
help=omode flag or see SUN/256 for more information.
- out=<out-table>
The location of the output table. This is usually a
filename to write to. If it is equal to the special value "-" (the
default) the output table will be written to standard output.
This parameter must only be given if omode has its default
value of "out".
- ofmt=<out-format>
Specifies the format in which the output table will be
written (one of the ones in SUN/256 - matching is case-insensitive and you can
use just the first few letters). If it has the special value
"
(auto)" (the default), then the output filename will be
examined to try to guess what sort of file is required usually by looking at
the extension. If it's not obvious from the filename what output format is
intended, an error will result.
This parameter must only be given if omode has its default
value of "out".
- ra=<expr>
Right ascension in degrees in the coordinate system for
the position of each row of the input table. This may simply be a column name,
or it may be an algebraic expression calculated from columns as explained in
SUN/256. If left blank, an attempt is made to guess from UCDs, column names
and unit annotations what expression to use.
- dec=<expr>
Declination in degrees in the coordinate system for the
position of each row of the input table. This may simply be a column name, or
it may be an algebraic expression calculated from columns as explained in
SUN/256. If left blank, an attempt is made to guess from UCDs, column names
and unit annotations what expression to use.
- sr=<expr/deg>
Expression which evaluates to the search radius in
degrees for the request at each row of the input table. This will often be a
constant numerical value, but may be the name or ID of a column in the input
table, or a function involving one.
- find=best|all|each
Determines which matches are retained.
- best: Only the matching query table row closest to the input table
row will be output. Input table rows with no matches will be omitted.
(Note this corresponds to the best1 option in the pair matching
commands, and best1 is a permitted alias).
- all: All query table rows which match the input table row will be
output. Input table rows with no matches will be omitted.
- each: There will be one output table row for each input table row.
If matches are found, the closest one from the query table will be output,
and in the case of no matches, the query table columns will be blank.
Determines whether an attempt will be made to restrict
searches in accordance with available footprint information. If this is set
true, then before any of the per-row queries are performed, an attempt may be
made to acquire footprint information about the servce. If such information
can be obtained, then queries which fall outside the footprint, and hence
which are known to yield no results, are skipped. This can speed up the search
considerably.
Currently, the only footprints available are those provided by the
CDS MOC (Multi-Order Coverage map) service, which covers VizieR and a few
other cone search services.
Determines the HEALPix Nside parameter for use with the
MOC footprint service. This tuning parameter determines the resolution of the
footprint if available. Larger values give better resolution, hence a better
chance of avoiding unnecessary queries, but processing them takes longer and
retrieving and storing them is more expensive.
The value must be a power of 2, and at the time of writing, the
MOC service will not supply footprints at resolutions greater than
nside=512, so it should be <=512.
Only used if usefoot=true.
- copycols=<colid-list>
List of columns from the input table which are to be
copied to the output table. Each column identified here will be prepended to
the columns of the combined output table, and its value for each row taken
from the input table row which provided the parameters of the query which
produced it. See SUN/256 for list syntax. The default setting is
"
*", which means that all columns from the input table are
included in the output.
- scorecol=<col-name>
Gives the name of a column in the output table to contain
the distance between the requested central position and the actual position of
the returned row. The distance returned is an angular distance in degrees. If
a null value is chosen, no distance column will appear in the output table.
- erract=abort|ignore|retry|retry<n>
Determines what will happen if any of the individual cone
search requests fails. By default the task aborts. That may be the best thing
to do, but for unreliable or poorly implemented services you may find that
some searches fail and others succeed so it can be best to continue operation
in the face of a few failures. The options are:
- abort: Failure of any query terminates the task.
- ignore: Failure of a query is treated the same as a query which
returns no rows.
- retry: Failed queries are retried until they succeed; an increasing
delay is introduced for each failure. Use with care - if the failure is
for some good, or at least reproducible reason this could prevent the task
from ever completing.
- retry<n>: Failed queries are retried at most a fixed number
<n> of times; an increasing delay is introduced for each
failure. If failures persist the task terminates.
- ostream=true|false
If set true, this will cause the operation to stream on
output, so that the output table is built up as the results are obtained from
the cone search service. The disadvantage of this is that some output modes
and formats need multiple passes through the data to work, so depending on the
output destination, the operation may fail if this is set. Use with care (or
be prepared for the operation to fail).
- fixcols=none|dups|all
Determines how input columns are renamed before use in
the output table. The choices are:
- none: columns are not renamed
- dups: columns which would otherwise have duplicate names in the
output will be renamed to indicate which table they came from
- all: all columns will be renamed to indicate which table they came
from
If columns are renamed, the new ones are determined by
suffix*
parameters.
- suffix0=<label>
If the
fixcols parameter is set so that input
columns are renamed for insertion into the output table, this parameter
determines how the renaming is done. It gives a suffix which is appended to
all renamed columns from the input table.
- suffix1=<label>
If the
fixcols parameter is set so that input
columns are renamed for insertion into the output table, this parameter
determines how the renaming is done. It gives a suffix which is appended to
all renamed columns from the cone result table.
- db=<jdbc-url>
URL which defines a connection to a database. This has
the form
jdbc:<subprotocol>:<subname> - the details are
database- and driver-dependent. Consult Sun's JDBC documentation and that for
the particular JDBC driver you are using for details. Note that the relevant
driver class will need to be on your classpath and referenced in the
jdbc.drivers system property as well for the connection to be made.
- user=<value>
User name for logging in to SQL database. Defaults to the
current username.
- password=<value>
Password for logging in to SQL database.
- dbtable=<table-name>
The name of the table in the SQL database which provides
the remote data.
- dbra=<sql-col>
The name of a column in the SQL database table
dbtable which gives the right ascension. Units are given by
dbunit.
- dbdec=<sql-col>
The name of a column in the SQL database table
dbtable which gives the declination. Units are given by
dbunit.
- dbunit=deg|rad
Units of the right ascension and declination columns
identified in the database table. May be either deg[rees] (the default) or
rad[ians].
- tiling=hpx<K>|healpixnest<K>|healpixring<K>|htm<K>
Describes the sky tiling scheme that is in use. One of
the following values may be used:
- hpxK: alias for healpixnestK
- healpixnestK: HEALPix using the Nest scheme at order K
- healpixringK: HEALPix using the Ring scheme at order K
- htmK: Hierarchical Triangular Mesh at level K
So for instance
hpx5 or
healpixnest5 would both indicate the
HEALPix NEST tiling scheme at order 5.
At level K, there are 12*4^K HEALPix pixels, or 8*4^K HTM pixels
on the sky. More information about these tiling schemes can be found at the
HEALPix and HTM web sites.
- dbtile=<sql-col>
The name of a column in the SQL database table
dbtable which contains a sky tiling pixel index. The tiling scheme is
given by the tiling parameter. Use of a tiling column is optional, but if
present (and if the column is indexed in the database table) it may serve to
speed up searches. Set to null if the database table contains no tiling column
or if you do not wish to use one.
- selectcols=<sql-cols>
An SQL expression for the list of columns to be selected
from the table in the database. A value of "
*" retrieves all
columns.
- where=<sql-condition>
An SQL expression further limiting the rows to be
selected from the database. This will be combined with the constraints on
position implied by the cone search centres and radii. The value of this
parameter should just be a condition, it should not contain the
WHERE
keyword. A null value indicates no additional criteria.
- preparesql=true|false
If true, the JDBC connection will use
PreparedStatements for the SQL SELECTs otherwise it will use simple
Statements. This is a tuning parameter and affects only performance. On
some database/driver combinations it's a lot faster set false (the default);
on others it may be faster, who knows?
