4 htsn-import \- Import XML files from The Sports Network into an RDBMS.
8 \fBhtsn-import\fR [OPTIONS] [FILES]
12 The Sports Network <http://www.sportsnetwork.com/> offers an XML feed
13 containing various sports news and statistics. Our sister program
14 \fBhtsn\fR is capable of retrieving the feed and saving the individual
15 XML documents contained therein. But what to do with them?
17 The purpose of \fBhtsn-import\fR is to take these XML documents and
18 get them into something we can use, a relational database management
19 system (RDBMS), otherwise known as a SQL database. The structure of
20 relational database, is, well, relational, and the feed XML is not. So
21 there is some work to do before the data can be imported into the
24 First, we must parse the XML. Each supported document type (see below)
25 has a full pickle/unpickle implementation (\(dqpickle\(dq is simply a
26 synonym for serialize here). That means that we parse the entire
27 document into a data structure, and if we pickle (serialize) that data
28 structure, we get the exact same XML document tha we started with.
30 This is important for two reasons. First, it serves as a second level
31 of validation. The first validation is performed by the XML parser,
32 but if that succeeds and unpicking fails, we know that something is
33 fishy. Second, we don't ever want to be surprised by some new element
34 or attribute showing up in the XML. The fact that we can unpickle the
35 whole thing now means that we won't be surprised in the future.
37 The aforementioned feature is especially important because we
38 automatically migrate the database schema every time we import a
39 document. If you attempt to import a \(dqnewsxml.dtd\(dq document, all
40 database objects relating to the news will be created if they do not
41 exist. We don't want the schema to change out from under us without
42 warning, so it's important that no XML be parsed that would result in
43 a different schema than we had previously. Since we can
44 pickle/unpickle everything already, this should be impossible.
46 .SH SUPPORTED DOCUMENT TYPES
48 The XML document types obtained from the feed are uniquely identified
49 by their DTDs. We currently support documents with the following DTDs:
51 AutoRacingResultsXML.dtd
53 Auto_Racing_Schedule_XML.dtd
57 Injuries_Detail_XML.dtd
78 Matchup_NBA_NHL_XML.dtd
80 MLB_Gaming_Matchup_XML.dtd
90 NBA_Gaming_Matchup_XML.dtd
92 NBA_Playoff_Matchup_XML.dtd
98 NCAA_FB_Preview_XML.dtd
100 NFL_NCAA_FB_Matchup_XML.dtd
108 WorldBaseballPreviewXML.dtd
116 Cbask_All_Tourn_Teams_XML.dtd
124 Cbask_Conf_Standings_XML.dtd
127 The GameInfo and SportInfo types do not have their own top-level
128 tables in the database. Instead, their raw XML is stored in either the
129 \(dqgame_info\(dq or \(dqsport_info\(dq table respectively.
133 At the top level (with two notable exceptions), we have one table for
134 each of the XML document types that we import. For example, the
135 documents corresponding to \fInewsxml.dtd\fR will have a table called
136 \(dqnews\(dq. All top-level tables contain two important fields,
137 \(dqxml_file_id\(dq and \(dqtime_stamp\(dq. The former is unique and
138 prevents us from inserting the same data twice. The time stamp on the
139 other hand lets us know when the data is old and can be removed. The
140 database schema make it possible to delete only the outdated top-level
141 records; all transient children should be removed by triggers.
143 These top-level tables will often have children. For example, each
144 news item has zero or more locations associated with it. The child
145 table will be named <parent>_<children>, which in this case
146 corresponds to \(dqnews_locations\(dq.
148 To relate the two, a third table may exist with name
149 <parent>__<child>. Note the two underscores. This prevents ambiguity
150 when the child table itself contains underscores. The table joining
151 \(dqnews\(dq with \(dqnews_locations\(dq is thus called
152 \(dqnews__news_locations\(dq. This is necessary when the child table
153 has a unique constraint; we don't want to blindly insert duplicate
154 records keyed to the parent. Instead we'd like to use the third table
155 to map an existing child to the new parent.
157 Where it makes sense, children are kept unique to prevent pointless
158 duplication. This slows down inserts, and speeds up reads (which are
159 much more frequent). There is a tradeoff to be made, however. For a
160 table with a small, fixed upper bound on the number of rows (like
161 \(dqodds_casinos\(dq), there is great benefit to de-duplication. The
162 total number of rows stays small, so inserts are still quick, and many
163 duplicate rows are eliminated.
165 But, with a table like \(dqodds_games\(dq, the number of games grows
166 quickly and without bound. It is therefore more beneficial to be able
167 to delete the old games (through an ON DELETE CASCADE, tied to
168 \(dqodds\(dq) than it is to eliminate duplication. A table like
169 \(dqnews_locations\(dq is somewhere in-between. It is hoped that the
170 unique constraint in the top-level table's \(dqxml_file_id\(dq will
171 prevent duplication in this case anyway.
173 The aforementioned exceptions are the \(dqgame_info\(dq and
174 \(dqsport_info\(dq tables. These tables contain the raw XML for a
175 number of DTDs that are not handled individually. This is partially
176 for backwards-compatibility with a legacy implementation, but is
177 mostly a stopgap due to a lack of resources at the moment. These two
178 tables (game_info and sport_info) still possess timestamps that allow
179 us to prune old data.
181 UML diagrams of the resulting database schema for each XML document
182 type are provided with the \fBhtsn-import\fR documentation.
184 .SH XML Schema Oddities
186 There are a number of problems with the XML on the wire. Even if we
187 construct the DTDs ourselves, the results are sometimes
188 inconsistent. Here we document a few of them.
193 The <Notes> elements here are supposed to be associated with a set of
194 <Game> elements, but since the pair
195 (<Notes>...</Notes><Game>...</Game>) can appear zero or more times,
196 this leads to ambiguity in parsing. We therefore ignore the notes
197 entirely (although a hack is employed to facilitate parsing).
202 There appear to be two types of weather documents; the first has
203 <listing> contained within <forecast> and the second has <forecast>
204 contained within <listing>. While it would be possible to parse both,
205 it would greatly complicate things. The first form is more common, so
206 that's all we support for now.
210 .IP \fB\-\-backend\fR,\ \fB\-b\fR
211 The RDBMS backend to use. Valid choices are \fISqlite\fR and
212 \fIPostgres\fR. Capitalization is important, sorry.
216 .IP \fB\-\-connection-string\fR,\ \fB\-c\fR
217 The connection string used for connecting to the database backend
218 given by the \fB\-\-backend\fR option. The default is appropriate for
219 the \fISqlite\fR backend.
221 Default: \(dq:memory:\(dq
223 .IP \fB\-\-log-file\fR
224 If you specify a file here, logs will be written to it (possibly in
225 addition to syslog). Can be either a relative or absolute path. It
226 will not be auto-rotated; use something like logrotate for that.
230 .IP \fB\-\-log-level\fR
231 How verbose should the logs be? We log notifications at four levels:
232 DEBUG, INFO, WARN, and ERROR. Specify the \(dqmost boring\(dq level of
233 notifications you would like to receive (in all-caps); more
234 interesting notifications will be logged as well. The debug output is
235 extremely verbose and will not be written to syslog even if you try.
239 .IP \fB\-\-remove\fR,\ \fB\-r\fR
240 Remove successfully processed files. If you enable this, you can see
241 at a glance which XML files are not being processed, because they're
242 all that should be left.
246 .IP \fB\-\-syslog\fR,\ \fB\-s\fR
247 Enable logging to syslog. On Windows this will attempt to communicate
248 (over UDP) with a syslog daemon on localhost, which will most likely
253 .SH CONFIGURATION FILE
255 Any of the command-line options mentioned above can be specified in a
256 configuration file instead. We first look for \(dqhtsn-importrc\(dq in
257 the system configuration directory. We then look for a file named
258 \(dq.htsn-importrc\(dq in the user's home directory. The latter will
261 The user's home directory is simply $HOME on Unix; on Windows it's
262 wherever %APPDATA% points. The system configuration directory is
263 determined by Cabal; the \(dqsysconfdir\(dq parameter during the
264 \(dqconfigure\(dq step is used.
266 The file's syntax is given by examples in the htsn-importrc.example file
267 (included with \fBhtsn-import\fR).
269 Options specified on the command-line override those in either
274 Import newsxml.xml into a preexisting sqlite database named \(dqfoo.sqlite3\(dq:
277 .I $ htsn-import --connection-string='foo.sqlite3' \\\\
278 .I " test/xml/newsxml.xml"
279 Successfully imported test/xml/newsxml.xml.
280 Imported 1 document(s) total.
283 Repeat the previous example, but delete newsxml.xml afterwards:
286 .I $ htsn-import --connection-string='foo.sqlite3' \\\\
287 .I " --remove test/xml/newsxml.xml"
288 Successfully imported test/xml/newsxml.xml.
289 Imported 1 document(s) total.
290 Removed processed file test/xml/newsxml.xml.
293 Use a Postgres database instead of the default Sqlite. This assumes
294 that you have a database named \(dqhtsn\(dq accessible to user
295 \(dqpostgres\(dq locally:
298 .I $ htsn-import --connection-string='dbname=htsn user=postgres' \\\\
299 .I " --backend=Postgres test/xml/newsxml.xml"
300 Successfully imported test/xml/newsxml.xml.
301 Imported 1 document(s) total.
307 Send bugs to michael@orlitzky.com.