doc/man1/htsn-import.1

   1 .TH htsn-import 1
   2
   3 .SH NAME
   4 htsn-import \- Import XML files from The Sports Network into an RDBMS.
   5
   6 .SH SYNOPSIS
   7
   8 \fBhtsn-import\fR [OPTIONS] [FILES]
   9
  10 .SH DESCRIPTION
  11 .P
  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?
  16 .P
  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
  22 database.
  23 .P
  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.
  29 .P
  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.
  36 .P
  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.
  45
  46 .SH SUPPORTED DOCUMENT TYPES
  47 .P
  48 The XML document types obtained from the feed are uniquely identified
  49 by their DTDs. We currently support documents with the following DTDs:
  50 .IP \[bu] 2
  51 Auto_Racing_Schedule_XML.dtd
  52 .IP \[bu]
  53 Heartbeat.dtd
  54 .IP \[bu]
  55 Injuries_Detail_XML.dtd
  56 .IP \[bu]
  57 injuriesxml.dtd
  58 .IP \[bu]
  59 MLB_Gaming_Matchup_XML.dtd (GameInfo)
  60 .IP \[bu]
  61 MLB_Lineup_XML.dtd (GameInfo)
  62 .IP \[bu]
  63 MLB_Matchup_XML.dtd (GameInfo)
  64 .IP \[bu]
  65 MLS_Preview_XML.dtd (GameInfo)
  66 .IP \[bu]
  67 mlbpreviewxml.dtd (GameInfo)
  68 .IP \[bu]
  69 NBA_Gaming_Matchup_XML.dtd (GameInfo)
  70 .IP \[bu]
  71 NBA_Playoff_Matchup_XML.dtd (GameInfo)
  72 .IP \[bu]
  73 NBALineupXML.dtd (GameInfo)
  74 .IP \[bu]
  75 nbapreviewxml.dtd (GameInfo)
  76 .IP \[bu]
  77 newsxml.dtd
  78 .IP \[bu]
  79 nhlpreviewxml.dtd (GameInfo)
  80 .IP \[bu]
  81 Odds_XML.dtd
  82 .IP \[bu]
  83 recapxml.dtd (GameInfo)
  84 .IP \[bu]
  85 scoresxml.dtd
  86 .IP \[bu]
  87 weatherxml.dtd
  88 .P
  89 The GameInfo and SportsInfo types do not have their own top-level
  90 tables in the database. Instead, their raw XML is stored in either the
  91 \(dqgame_info\(dq or \(dqsports_info\(dq table respectively.
  92
  93 .SH DATABASE SCHEMA
  94 .P
  95 At the top level (with two notable exceptions), we have one table for
  96 each of the XML document types that we import. For example, the
  97 documents corresponding to \fInewsxml.dtd\fR will have a table called
  98 \(dqnews\(dq. All top-level tables contain two important fields,
  99 \(dqxml_file_id\(dq and \(dqtime_stamp\(dq. The former is unique and
 100 prevents us from inserting the same data twice. The time stamp on the
 101 other hand lets us know when the data is old and can be removed. The
 102 database schema make it possible to delete only the outdated top-level
 103 records; all transient children should be removed by triggers.
 104 .P
 105 These top-level tables will often have children. For example, each
 106 news item has zero or more locations associated with it. The child
 107 table will be named <parent>_<children>, which in this case
 108 corresponds to \(dqnews_locations\(dq.
 109 .P
 110 To relate the two, a third table may exist with name
 111 <parent>__<child>. Note the two underscores. This prevents ambiguity
 112 when the child table itself contains underscores. The table joining
 113 \(dqnews\(dq with \(dqnews_locations\(dq is thus called
 114 \(dqnews__news_locations\(dq. This is necessary when the child table
 115 has a unique constraint; we don't want to blindly insert duplicate
 116 records keyed to the parent. Instead we'd like to use the third table
 117 to map an existing child to the new parent.
 118 .P
 119 Where it makes sense, children are kept unique to prevent pointless
 120 duplication. This slows down inserts, and speeds up reads (which are
 121 much more frequent). There is a tradeoff to be made, however. For a
 122 table with a small, fixed upper bound on the number of rows (like
 123 \(dqodds_casinos\(dq), there is great benefit to de-duplication. The
 124 total number of rows stays small, so inserts are still quick, and many
 125 duplicate rows are eliminated.
 126 .P
 127 But, with a table like \(dqodds_games\(dq, the number of games grows
 128 quickly and without bound. It is therefore more beneficial to be able
 129 to delete the old games (through an ON DELETE CASCADE, tied to
 130 \(dqodds\(dq) than it is to eliminate duplication. A table like
 131 \(dqnews_locations\(dq is somewhere in-between. It is hoped that the
 132 unique constraint in the top-level table's \(dqxml_file_id\(dq will
 133 prevent duplication in this case anyway.
 134 .P
 135 The aforementioned exceptions are the \(dqgame_info\(dq and
 136 \(dqsports_info\(dq tables. These tables contain the raw XML for a
 137 number of DTDs that are not handled individually. This is partially
 138 for backwards-compatibility with a legacy implementation, but is
 139 mostly a stopgap due to a lack of resources at the moment. These two
 140 tables (game_info and sports_info) still possess timestamps that allow
 141 us to prune old data.
 142 .P
 143 UML diagrams of the resulting database schema for each XML document
 144 type are provided with the \fBhtsn-import\fR documentation.
 145
 146 .SH XML Schema Oddities
 147 .P
 148 There are a number of problems with the XML on the wire. Even if we
 149 construct the DTDs ourselves, the results are sometimes
 150 inconsistent. Here we document a few of them.
 151
 152 .IP \[bu] 2
 153 Odds_XML.dtd
 154
 155 The <Notes> elements here are supposed to be associated with a set of
 156 <Game> elements, but since the pair
 157 (<Notes>...</Notes><Game>...</Game>) can appear zero or more times,
 158 this leads to ambiguity in parsing. We therefore ignore the notes
 159 entirely (although a hack is employed to facilitate parsing).
 160
 161 .IP \[bu]
 162 weatherxml.dtd
 163
 164 There appear to be two types of weather documents; the first has
 165 <listing> contained within <forecast> and the second has <forecast>
 166 contained within <listing>. While it would be possible to parse both,
 167 it would greatly complicate things. The first form is more common, so
 168 that's all we support for now.
 169
 170 .SH OPTIONS
 171
 172 .IP \fB\-\-backend\fR,\ \fB\-b\fR
 173 The RDBMS backend to use. Valid choices are \fISqlite\fR and
 174 \fIPostgres\fR. Capitalization is important, sorry.
 175
 176 Default: Sqlite
 177
 178 .IP \fB\-\-connection-string\fR,\ \fB\-c\fR
 179 The connection string used for connecting to the database backend
 180 given by the \fB\-\-backend\fR option. The default is appropriate for
 181 the \fISqlite\fR backend.
 182
 183 Default: \(dq:memory:\(dq
 184
 185 .IP \fB\-\-log-file\fR
 186 If you specify a file here, logs will be written to it (possibly in
 187 addition to syslog). Can be either a relative or absolute path. It
 188 will not be auto-rotated; use something like logrotate for that.
 189
 190 Default: none
 191
 192 .IP \fB\-\-log-level\fR
 193 How verbose should the logs be? We log notifications at four levels:
 194 DEBUG, INFO, WARN, and ERROR. Specify the \(dqmost boring\(dq level of
 195 notifications you would like to receive (in all-caps); more
 196 interesting notifications will be logged as well. The debug output is
 197 extremely verbose and will not be written to syslog even if you try.
 198
 199 Default: INFO
 200
 201 .IP \fB\-\-remove\fR,\ \fB\-r\fR
 202 Remove successfully processed files. If you enable this, you can see
 203 at a glance which XML files are not being processed, because they're
 204 all that should be left.
 205
 206 Default: disabled
 207
 208 .IP \fB\-\-syslog\fR,\ \fB\-s\fR
 209 Enable logging to syslog. On Windows this will attempt to communicate
 210 (over UDP) with a syslog daemon on localhost, which will most likely
 211 not work.
 212
 213 Default: disabled
 214
 215 .SH CONFIGURATION FILE
 216 .P
 217 Any of the command-line options mentioned above can be specified in a
 218 configuration file instead. We first look for \(dqhtsn-importrc\(dq in
 219 the system configuration directory. We then look for a file named
 220 \(dq.htsn-importrc\(dq in the user's home directory. The latter will
 221 override the former.
 222 .P
 223 The user's home directory is simply $HOME on Unix; on Windows it's
 224 wherever %APPDATA% points. The system configuration directory is
 225 determined by Cabal; the \(dqsysconfdir\(dq parameter during the
 226 \(dqconfigure\(dq step is used.
 227 .P
 228 The file's syntax is given by examples in the htsn-importrc.example file
 229 (included with \fBhtsn-import\fR).
 230 .P
 231 Options specified on the command-line override those in either
 232 configuration file.
 233
 234 .SH EXAMPLES
 235 .IP \[bu] 2
 236 Import newsxml.xml into a preexisting sqlite database named \(dqfoo.sqlite3\(dq:
 237
 238 .nf
 239 .I $ htsn-import --connection-string='foo.sqlite3' \\\\
 240 .I "              test/xml/newsxml.xml"
 241 Successfully imported test/xml/newsxml.xml.
 242 Imported 1 document(s) total.
 243 .fi
 244 .IP \[bu]
 245 Repeat the previous example, but delete newsxml.xml afterwards:
 246
 247 .nf
 248 .I $ htsn-import --connection-string='foo.sqlite3' \\\\
 249 .I "              --remove test/xml/newsxml.xml"
 250 Successfully imported test/xml/newsxml.xml.
 251 Imported 1 document(s) total.
 252 Removed processed file test/xml/newsxml.xml.
 253 .fi
 254 .IP \[bu]
 255 Use a Postgres database instead of the default Sqlite. This assumes
 256 that you have a database named \(dqhtsn\(dq accessible to user
 257 \(dqpostgres\(dq locally:
 258
 259 .nf
 260 .I $ htsn-import --connection-string='dbname=htsn user=postgres' \\\\
 261 .I "              --backend=Postgres test/xml/newsxml.xml"
 262 Successfully imported test/xml/newsxml.xml.
 263 Imported 1 document(s) total.
 264 .fi
 265
 266 .SH BUGS
 267
 268 .P
 269 Send bugs to michael@orlitzky.com.