.TH htsn-import 1

.SH NAME
htsn-import \- Import XML files from The Sports Network into an RDBMS.

.SH SYNOPSIS

\fBhtsn-import\fR [OPTIONS] [FILES]

.SH DESCRIPTION
.P
The Sports Network <http://www.sportsnetwork.com/> offers an XML feed
containing various sports news and statistics. Our sister program
\fBhtsn\fR is capable of retrieving the feed and saving the individual
XML documents contained therein. But what to do with them?
.P
The purpose of \fBhtsn-import\fR is to take these XML documents and
get them into something we can use, a relational database management
system (RDBMS), otherwise known as a SQL database. The structure of
relational database, is, well, relational, and the feed XML is not. So
there is some work to do before the data can be imported into the
database.
.P
First, we must parse the XML. Each supported document type (see below)
has a full pickle/unpickle implementation (\(dqpickle\(dq is simply a
synonym for serialize here). That means that we parse the entire
document into a data structure, and if we pickle (serialize) that data
structure, we get the exact same XML document tha we started with.
.P
This is important for two reasons. First, it serves as a second level
of validation. The first validation is performed by the XML parser,
but if that succeeds and unpicking fails, we know that something is
fishy. Second, we don't ever want to be surprised by some new element
or attribute showing up in the XML. The fact that we can unpickle the
whole thing now means that we won't be surprised in the future.
.P
The aforementioned feature is especially important because we
automatically migrate the database schema every time we import a
document. If you attempt to import a \(dqnewsxml.dtd\(dq document, all
database objects relating to the news will be created if they do not
exist. We don't want the schema to change out from under us without
warning, so it's important that no XML be parsed that would result in
a different schema than we had previously. Since we can
pickle/unpickle everything already, this should be impossible.

.SH SUPPORTED DOCUMENT TYPES
.P
The XML document types obtained from the feed are uniquely identified
by their DTDs. We currently support documents with the following DTDs:
.IP \[bu] 2
Heartbeat.dtd
.IP \[bu]
newsxml.dtd
.IP \[bu]
Injuries_Detail_XML.dtd
.IP \[bu]
injuriesxml.dtd
.IP \[bu]
Odds_XML.dtd
.IP \[bu]
weatherxml.dtd

.SH DATABASE SCHEMA
.P
At the top level, we have one table for each of the XML document types
that we import. For example, the documents corresponding to
\fInewsxml.dtd\fR will have a table called \(dqnews\(dq. All top-level
tables contain two important fields, \(dqxml_file_id\(dq and
\(dqtime_stamp\(dq. The former is unique and prevents us from
inserting the same data twice. The time stamp on the other hand lets
us know when the data is old and can be removed. The database schema
make it possible to delete only the outdated top-level records; all
transient children should be removed by triggers.
.P
These top-level tables will often have children. For example, each
news item has zero or more locations associated with it. The child
table will be named <parent>_<children>, which in this case
corresponds to \(dqnews_locations\(dq.
.P
To relate the two, a third table may exist with name
<parent>__<child>. Note the two underscores. This prevents ambiguity
when the child table itself contains underscores. The table joining
\(dqnews\(dq with \(dqnews_locations\(dq is thus called
\(dqnews__news_locations\(dq. This is necessary when the child table
has a unique constraint; we don't want to blindly insert duplicate
records keyed to the parent. Instead we'd like to use the third table
to map an existing child to the new parent.
.P
Where it makes sense, children are kept unique to prevent pointless
duplication. This slows down inserts, and speeds up reads (which are
much more frequent). There is a tradeoff to be made, however. For a
table with a small, fixed upper bound on the number of rows (like
\(dqodds_casinos\(dq), there is great benefit to de-duplication. The
total number of rows stays small, so inserts are still quick, and many
duplicate rows are eliminated.
.P
But, with a table like \(dqodds_games\(dq, the number of games grows
quickly and without bound. It is therefore more beneficial to be able
to delete the old games (through an ON DELETE CASCADE, tied to
\(dqodds\(dq) than it is to eliminate duplication. A table like
\(dqnews_locations\(dq is somewhere in-between. It is hoped that the
unique constraint in the top-level table's \(dqxml_file_id\(dq will
prevent duplication in this case anyway.
.P
UML diagrams of the resulting database schema for each XML document
type are provided with the \fBhtsn-import\fR documentation.

.SH XML Schema Oddities
.P
There are a number of problems with the XML on the wire. Even if we
construct the DTDs ourselves, the results are sometimes
inconsistent. Here we document a few of them.

.IP \[bu]
2 Odds_XML.dtd

The <Notes> elements here are supposed to be associated with a set of
<Game> elements, but since the pair
(<Notes>...</Notes><Game>...</Game>) can appear zero or more times,
this leads to ambiguity in parsing. We therefore ignore the notes
entirely (although a hack is employed to facilitate parsing).

.IP \[bu]
weatherxml.dtd

There appear to be two types of weather documents; the first has
<listing> contained within <forecast> and the second has <forecast>
contained within <listing>. While it would be possible to parse both,
it would greatly complicate things. The first form is more common, so
that's all we support for now.

.SH OPTIONS

.IP \fB\-\-backend\fR,\ \fB\-b\fR
The RDBMS backend to use. Valid choices are \fISqlite\fR and
\fIPostgres\fR. Capitalization is important, sorry.

Default: Sqlite

.IP \fB\-\-connection-string\fR,\ \fB\-c\fR
The connection string used for connecting to the database backend
given by the \fB\-\-backend\fR option. The default is appropriate for
the \fISqlite\fR backend.

Default: \(dq:memory:\(dq

.IP \fB\-\-log-file\fR
If you specify a file here, logs will be written to it (possibly in
addition to syslog). Can be either a relative or absolute path. It
will not be auto-rotated; use something like logrotate for that.

Default: none

.IP \fB\-\-log-level\fR
How verbose should the logs be? We log notifications at three levels:
INFO, WARN, and ERROR. Specify the \(dqmost boring\(dq level of
notifications you would like to receive (in all-caps); more
interesting notifications will be logged as well.

Default: INFO

.IP \fB\-\-remove\fR,\ \fB\-r\fR
Remove successfully processed files. If you enable this, you can see
at a glance which XML files are not being processed, because they're
all that should be left.

Default: disabled

.IP \fB\-\-syslog\fR,\ \fB\-s\fR
Enable logging to syslog. On Windows this will attempt to communicate
(over UDP) with a syslog daemon on localhost, which will most likely
not work.

Default: disabled

.SH CONFIGURATION FILE
.P
Any of the command-line options mentioned above can be specified in a
configuration file instead. We first look for \(dqhtsn-importrc\(dq in
the system configuration directory. We then look for a file named
\(dq.htsn-importrc\(dq in the user's home directory. The latter will
override the former.
.P
The user's home directory is simply $HOME on Unix; on Windows it's
wherever %APPDATA% points. The system configuration directory is
determined by Cabal; the \(dqsysconfdir\(dq parameter during the
\(dqconfigure\(dq step is used.
.P
The file's syntax is given by examples in the htsn-importrc.example file
(included with \fBhtsn-import\fR).
.P
Options specified on the command-line override those in either
configuration file.

.SH EXAMPLES
.IP \[bu] 2
Import newsxml.xml into a preexisting sqlite database named \(dqfoo.sqlite3\(dq:

.nf
.I $ htsn-import --connection-string='foo.sqlite3' \\\\
.I "              test/xml/newsxml.xml"
Successfully imported test/xml/newsxml.xml.
Imported 1 document(s) total.
.fi
.IP \[bu]
Repeat the previous example, but delete newsxml.xml afterwards:

.nf
.I $ htsn-import --connection-string='foo.sqlite3' \\\\
.I "              --remove test/xml/newsxml.xml"
Successfully imported test/xml/newsxml.xml.
Imported 1 document(s) total.
Removed processed file test/xml/newsxml.xml.
.fi
.IP \[bu]
Use a Postgres database instead of the default Sqlite. This assumes
that you have a database named \(dqhtsn\(dq accessible to user
\(dqpostgres\(dq locally:

.nf
.I $ htsn-import --connection-string='dbname=htsn user=postgres' \\\\
.I "              --backend=Postgres test/xml/newsxml.xml"
Successfully imported test/xml/newsxml.xml.
Imported 1 document(s) total.
.fi

.SH BUGS

.P
Send bugs to michael@orlitzky.com.