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 Auto_Racing_Schedule_XML.dtd
55 Injuries_Detail_XML.dtd
76 Matchup_NBA_NHL_XML.dtd
78 MLB_Gaming_Matchup_XML.dtd
88 NBA_Gaming_Matchup_XML.dtd
90 NBA_Playoff_Matchup_XML.dtd
96 NCAA_FB_Preview_XML.dtd
98 NFL_NCAA_FB_Matchup_XML.dtd
106 WorldBaseballPreviewXML.dtd
114 Cbask_All_Tourn_Teams_XML.dtd
121 The GameInfo and SportInfo types do not have their own top-level
122 tables in the database. Instead, their raw XML is stored in either the
123 \(dqgame_info\(dq or \(dqsport_info\(dq table respectively.
127 At the top level (with two notable exceptions), we have one table for
128 each of the XML document types that we import. For example, the
129 documents corresponding to \fInewsxml.dtd\fR will have a table called
130 \(dqnews\(dq. All top-level tables contain two important fields,
131 \(dqxml_file_id\(dq and \(dqtime_stamp\(dq. The former is unique and
132 prevents us from inserting the same data twice. The time stamp on the
133 other hand lets us know when the data is old and can be removed. The
134 database schema make it possible to delete only the outdated top-level
135 records; all transient children should be removed by triggers.
137 These top-level tables will often have children. For example, each
138 news item has zero or more locations associated with it. The child
139 table will be named <parent>_<children>, which in this case
140 corresponds to \(dqnews_locations\(dq.
142 To relate the two, a third table may exist with name
143 <parent>__<child>. Note the two underscores. This prevents ambiguity
144 when the child table itself contains underscores. The table joining
145 \(dqnews\(dq with \(dqnews_locations\(dq is thus called
146 \(dqnews__news_locations\(dq. This is necessary when the child table
147 has a unique constraint; we don't want to blindly insert duplicate
148 records keyed to the parent. Instead we'd like to use the third table
149 to map an existing child to the new parent.
151 Where it makes sense, children are kept unique to prevent pointless
152 duplication. This slows down inserts, and speeds up reads (which are
153 much more frequent). There is a tradeoff to be made, however. For a
154 table with a small, fixed upper bound on the number of rows (like
155 \(dqodds_casinos\(dq), there is great benefit to de-duplication. The
156 total number of rows stays small, so inserts are still quick, and many
157 duplicate rows are eliminated.
159 But, with a table like \(dqodds_games\(dq, the number of games grows
160 quickly and without bound. It is therefore more beneficial to be able
161 to delete the old games (through an ON DELETE CASCADE, tied to
162 \(dqodds\(dq) than it is to eliminate duplication. A table like
163 \(dqnews_locations\(dq is somewhere in-between. It is hoped that the
164 unique constraint in the top-level table's \(dqxml_file_id\(dq will
165 prevent duplication in this case anyway.
167 The aforementioned exceptions are the \(dqgame_info\(dq and
168 \(dqsport_info\(dq tables. These tables contain the raw XML for a
169 number of DTDs that are not handled individually. This is partially
170 for backwards-compatibility with a legacy implementation, but is
171 mostly a stopgap due to a lack of resources at the moment. These two
172 tables (game_info and sport_info) still possess timestamps that allow
173 us to prune old data.
175 UML diagrams of the resulting database schema for each XML document
176 type are provided with the \fBhtsn-import\fR documentation.
178 .SH XML Schema Oddities
180 There are a number of problems with the XML on the wire. Even if we
181 construct the DTDs ourselves, the results are sometimes
182 inconsistent. Here we document a few of them.
187 The <Notes> elements here are supposed to be associated with a set of
188 <Game> elements, but since the pair
189 (<Notes>...</Notes><Game>...</Game>) can appear zero or more times,
190 this leads to ambiguity in parsing. We therefore ignore the notes
191 entirely (although a hack is employed to facilitate parsing).
196 There appear to be two types of weather documents; the first has
197 <listing> contained within <forecast> and the second has <forecast>
198 contained within <listing>. While it would be possible to parse both,
199 it would greatly complicate things. The first form is more common, so
200 that's all we support for now.
204 .IP \fB\-\-backend\fR,\ \fB\-b\fR
205 The RDBMS backend to use. Valid choices are \fISqlite\fR and
206 \fIPostgres\fR. Capitalization is important, sorry.
210 .IP \fB\-\-connection-string\fR,\ \fB\-c\fR
211 The connection string used for connecting to the database backend
212 given by the \fB\-\-backend\fR option. The default is appropriate for
213 the \fISqlite\fR backend.
215 Default: \(dq:memory:\(dq
217 .IP \fB\-\-log-file\fR
218 If you specify a file here, logs will be written to it (possibly in
219 addition to syslog). Can be either a relative or absolute path. It
220 will not be auto-rotated; use something like logrotate for that.
224 .IP \fB\-\-log-level\fR
225 How verbose should the logs be? We log notifications at four levels:
226 DEBUG, INFO, WARN, and ERROR. Specify the \(dqmost boring\(dq level of
227 notifications you would like to receive (in all-caps); more
228 interesting notifications will be logged as well. The debug output is
229 extremely verbose and will not be written to syslog even if you try.
233 .IP \fB\-\-remove\fR,\ \fB\-r\fR
234 Remove successfully processed files. If you enable this, you can see
235 at a glance which XML files are not being processed, because they're
236 all that should be left.
240 .IP \fB\-\-syslog\fR,\ \fB\-s\fR
241 Enable logging to syslog. On Windows this will attempt to communicate
242 (over UDP) with a syslog daemon on localhost, which will most likely
247 .SH CONFIGURATION FILE
249 Any of the command-line options mentioned above can be specified in a
250 configuration file instead. We first look for \(dqhtsn-importrc\(dq in
251 the system configuration directory. We then look for a file named
252 \(dq.htsn-importrc\(dq in the user's home directory. The latter will
255 The user's home directory is simply $HOME on Unix; on Windows it's
256 wherever %APPDATA% points. The system configuration directory is
257 determined by Cabal; the \(dqsysconfdir\(dq parameter during the
258 \(dqconfigure\(dq step is used.
260 The file's syntax is given by examples in the htsn-importrc.example file
261 (included with \fBhtsn-import\fR).
263 Options specified on the command-line override those in either
268 Import newsxml.xml into a preexisting sqlite database named \(dqfoo.sqlite3\(dq:
271 .I $ htsn-import --connection-string='foo.sqlite3' \\\\
272 .I " test/xml/newsxml.xml"
273 Successfully imported test/xml/newsxml.xml.
274 Imported 1 document(s) total.
277 Repeat the previous example, but delete newsxml.xml afterwards:
280 .I $ htsn-import --connection-string='foo.sqlite3' \\\\
281 .I " --remove test/xml/newsxml.xml"
282 Successfully imported test/xml/newsxml.xml.
283 Imported 1 document(s) total.
284 Removed processed file test/xml/newsxml.xml.
287 Use a Postgres database instead of the default Sqlite. This assumes
288 that you have a database named \(dqhtsn\(dq accessible to user
289 \(dqpostgres\(dq locally:
292 .I $ htsn-import --connection-string='dbname=htsn user=postgres' \\\\
293 .I " --backend=Postgres test/xml/newsxml.xml"
294 Successfully imported test/xml/newsxml.xml.
295 Imported 1 document(s) total.
301 Send bugs to michael@orlitzky.com.