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118 database schema make it possible to delete only the outdated top-level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