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Help pages for DBview

Start screen

To personalize the DBViewer, a new user should first log in with his or her username. Optionally, a user can click a project if wanted (log-in + project: see top row). After these steps the user can click one of the table categories listed on the start sceen (but also present at the top right). Each category consists of a list of tables, with each table having, if available, a link to a table description. After clicking a table, the user is shown a query screen with lots of attributes to be queried.

Query Page

The query page consists of a tree view of the current class and all its dependencies and attributes. The dependencies can be unfolded, the attributes can be used to query on. If a dependency is unfolded when the submit button is clicked the output will contain the attributes of this dependency. There are three different kinds of attributes to query on :

  • Dates; a date can be given as yyyy-mm-dd or yyyy-mm-dd hh:mm:ss, so with or without a time component
  • Numbers; integers like 1, 100 and floats like 3.4, 123.45
  • Strings; querying on strings is case insensitive, see the operator like for wildcards

The following operators are supported, although not every attribute type supports all of them :

  • <; The less then operator
  • >; The greater then operator
  • =; The is equal to operator
  • !=; The is not equal to operator
  • like; The like operator is used to compare strings, use % as a wildcard for zero or multiple characters, use _ as a wildcard for a single character
  • not like; The not like operator
  • between; The between operator queries for results between the given values, specify as : value1,value2
  • not between; The inverse of the between operator, specify as : value1,value2

Parameters

There are two sets of parameters: general parameters and local parameters. The general parameters can be accessed from the top row under 'preferences'. The local parameters are always located above the query page. Below is a description of all parameters. Suggestions for additional parameters are welcome! Please use the contact page (see top row).

  • export options: Export options:
    • Comma separated values: Table-output as comma-separated-values
    • pickle-d lists: exports table as list of lists in python-format to be read by Unpickler routine
    • HTML (Default): output is shown in browser
    • Links to download all files: A text file is returned containing links to all FITS files present in the displayed table.
    • SQL statement: SQL query as text-file
    • VOTable XML: XML VOTable format, compatible with current VO programs.
    • FITS: write table in fits format (reference: Fits definition).
  • fcontext_project_only: YES (default): only data belonging to the set project is visible
  • hide_columns: YES (default): Hide the less interesting columns, these columns contain mostly default values for all objects.
  • numrows: This specifies the number of rows visible on the output page, where numrow means unlimited. Note, in the browser the upper limit to be shown is 1000, for the other export options an ulimited amount of rows can be written to the output.
  • show_comments: Show a link to the Comments per object in the result table
  • show_expanded: NO (Default); YES: all attributes in expanded leafs will be shown in the DBViewer result page, this can be very slow or could even crash when a user requests very deep and/or large trees
  • SQLbox_height: This number specifies the height of the SQL box containing the SQL (see bottom query-output page)
  • SQLbox_width: This number specifies the width of the SQL box containing the SQL (see bottom query-output page)
  • use_checkboxes: NO (default): YES: checkboxes can be used to select rows; Manual SQL is not possible anymore when selecting this option.

SAMP connection

After querying, the output is visible in the dbviewer. This output can be send to external (VO) programs like topcat etc. In order for this to work, three steps should be carried out, which are shown as links above the header of the table.

  • Step 1: Test. Java should be available within your browser. Step 1 provides a test that should return True. [TBD, where to place the java .so files]
  • Step 2: Connect. In order to connect to external tools from within the browser, we make use of SAMP and the java-tool WebSAMPConnector. After clicking, the WebSAMPConnector icon should turn green. If a java-error message is returned and/or the icon stays black, it is recommended to follow the following recipe; this recipe will basically refresh your java configuration directory in your home directory. The following steps should be taken:

    • Close your browser
    • Rename your .java directory in $HOME to something like .java.old
    • Start your browser
    • Click the SAMP connector in the dbview query output page.

    Java will store its setting at $HOME/.java. To restore your old java settings, close the browser and rename the .java.old directory to .java.

  • Step 3: Broadcast: this should send the table to the VO tool. NOTE: a VO tool should have been opened in advance.

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