root/main/trunk/greenstone2/perllib/gssql.pm @ 32571

Revision 32571, 24.3 KB (checked in by ak19, 20 months ago)

Optimised the SQL DB delete operations in case there are several in one building phase, by preparing the delete SQL statement once and storing it then executing it each time there's a delete, rather than calling do() which will both prepare the del SQL statement each time and execute it each time

Line 
1###########################################################################
2#
3# gssql.pm -- DBI for SQL related utility functions used by
4# GreenstoneSQLPlugout and hereafter by GreenstoneSQLPlugin too.
5# A component of the Greenstone digital library software
6# from the New Zealand Digital Library Project at the
7# University of Waikato, New Zealand.
8#
9# Copyright (C) 1999 New Zealand Digital Library Project
10#
11# This program is free software; you can redistribute it and/or modify
12# it under the terms of the GNU General Public License as published by
13# the Free Software Foundation; either version 2 of the License, or
14# (at your option) any later version.
15#
16# This program is distributed in the hope that it will be useful,
17# but WITHOUT ANY WARRANTY; without even the implied warranty of
18# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
19# GNU General Public License for more details.
20#
21# You should have received a copy of the GNU General Public License
22# along with this program; if not, write to the Free Software
23# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24#
25###########################################################################
26
27package gssql;
28
29use strict;
30no strict 'refs';
31no strict 'subs';
32
33use DBI; # the central package for this module used by GreenstoneSQL Plugout and Plugin
34
35# Need params_map keys:
36# - collection_name
37# - db_encoding (db content encoding) - MySQL can set this at server, db, table levels. For MySQL
38# we set the enc during connect at server level. Not sure whether other DB's support it at the
39# same levels.
40
41# For connection to MySQL, need:
42#  - db_driver, db_client_user, db_client_pwd, db_host, (db_port not used at present)
43# So these will be parameterised, but in a hashmap, for just the connect method.
44
45# Parameterise (one or more methods may use them):
46# - db_name (which is the GS3 sitename)
47
48# TODO: add infrastructure for db_port, AutoCommit etc
49# For port, see https://stackoverflow.com/questions/2248665/perl-script-to-connect-to-mysql-server-port-3307
50
51sub new
52
53    my $class = shift(@_);
54   
55    my ($params_map) = @_;
56   
57    # library_url: to be specified on the cmdline if not using a GS-included web server
58    # the GSDL_LIBRARY_URL env var is useful when running cmdline buildcol.pl in the linux package manager versions of GS3
59   
60    # https://stackoverflow.com/questions/7083453/copying-a-hashref-in-perl
61    # Making a shallow copy works, and can handle unknown params:
62    #my $self = $params_map;
63
64    # but being explicit for class params needed for MySQL:
65    my $self = {
66    'collection_name' => $params_map->{'collection_name'},
67    'verbosity' => $params_map->{'verbosity'} || 1
68    };
69
70    # The db_encoding option is presently not passed in to this constructor as parameter.
71    # Placed here to indicate it's sort of optional.
72    # Since docxml are all in utf8, the contents of the GS SQL database should be too,
73    # So making utf8 the hidden default at present.
74    $self->{'db_encoding'} = $params_map->{'db_encoding'} || "utf8";
75   
76    $self = bless($self, $class);   
77
78    $self->{'tablename_prefix'} = $self->sanitize_name($params_map->{'collection_name'});
79   
80    return $self;
81}
82
83
84#################################
85
86# Database access related functions
87# http://g2pc1.bu.edu/~qzpeng/manual/MySQL%20Commands.htm
88# https://www.guru99.com/insert-into.html
89
90# TODO Q: What on cancelling a build: delete table? But what if it was a rebuild and the rebuild is cancelled (not the original build)?
91# Do we create a copy of the orig database as backup, then start populating current db, and if cancelled, delete current db and RENAME backup table to current?
92# https://stackoverflow.com/questions/3280006/duplicating-a-mysql-table-indexes-and-data
93# BUT what if the table is HUGE? (Think of a collection with millions of docs.) Huge overhead in copying?
94# The alternative is we just quit on cancel, but then: cancel could leave the table in a partial committed state, with no way of rolling back.
95# Unless they do a full rebuild, which will recreate the table from scratch?
96# SOLUTION-> rollback transaction on error, see https://www.effectiveperlprogramming.com/2010/07/set-custom-dbi-error-handlers/
97# But then should set AutoCommit to off on connection, and remember to commit every time
98
99#################
100# Database functions that use the perl DBI module (with the DBD driver module for mysql)
101#################
102
103################### BASIC DB OPERATIONS ##################
104
105# THE NEW DB FUNCTIONS
106# NOTE: FULLTEXT is a reserved keyword in (My)SQL. So we can't name a table or any of its columns "fulltext".
107# https://dev.mysql.com/doc/refman/5.5/en/keywords.html
108
109# TODO: Consider AutoCommit status (and Autocommit off allowing commit or rollback for GS coll build cancel) later
110
111# TODO: where should the defaults for these params be, here or in GS-SQLPlugin/Plugout?
112sub connect_to_db {
113    my $self= shift (@_);
114    my ($params_map) = @_;
115    # For proper utf8 support in MySQL, encoding should be 'utf8mb4' as 'utf8' is insufficient
116    my $db_enc = "utf8mb4" if $self->{'db_encoding'} eq "utf8";
117
118    # these are the params for connecting to MySQL
119    my $db_driver = $params_map->{'db_driver'} || "mysql";
120    my $db_user = $params_map->{'db_client_user'} || "root";
121    my $db_pwd = $params_map->{'db_client_pwd'}; # even if undef, we'll see a sensible error message
122                                           # when connect fails
123    my $db_host = $params_map->{'db_host'} || "127.0.0.1";
124    # localhost doesn't work for us, but 127.0.0.1 works
125    # https://metacpan.org/pod/DBD::mysql
126    # "The hostname, if not specified or specified as '' or 'localhost', will default to a MySQL server
127    # running on the local machine using the default for the UNIX socket. To connect to a MySQL server
128    # on the local machine via TCP, you must specify the loopback IP address (127.0.0.1) as the host."
129    #my $connect_str = "dbi:$db_driver:database=$db_name;host=$db_host";
130    my $connect_str = "dbi:$db_driver:host=$db_host"; # don't provide db - allows checking the db exists later when loading the db
131
132    if($self->{'verbosity'}) {
133    print STDERR "Away to make connection to $db_driver database with:\n";
134    print STDERR " - hostname $db_host; username: $db_user";
135    print STDERR "; and the provided password" if $db_pwd;
136    print STDERR "\nAssuming the mysql server has been started with: --character_set_server=utf8mb4\n" if $db_driver eq "mysql";
137    }
138   
139    my $dbh = DBI->connect("$connect_str", $db_user, $db_pwd,
140               {
141                   ShowErrorStatement => 1, # more informative as DBI will append failed SQL stmt to error message
142                   PrintError => 1, # on by default, but being explicit
143                   RaiseError => 0, # off by default, but being explicit
144                   AutoCommit => 1, # on by default, but being explicit
145                   mysql_enable_utf8mb4 => 1 # tells MySQL to use UTF-8 for communication and tells DBD::mysql to decode the data, see https://stackoverflow.com/questions/46727362/perl-mysql-utf8mb4-issue-possible-bug
146               });
147
148    if(!$dbh) {
149    # NOTE, despite handle dbh being undefined, error code will be in DBI->err (note caps)
150    return 0;   
151    }
152
153    # set encoding https://metacpan.org/pod/DBD::mysql
154    # https://dev.mysql.com/doc/refman/5.7/en/charset.html
155    # https://dev.mysql.com/doc/refman/5.7/en/charset-conversion.html
156    # Setting the encoding at db server level: $dbh->do("set NAMES '" . $db_enc . "'");
157    # HOWEVER:
158    # It turned out insufficient setting the encoding to utf8, as that only supports utf8 chars that
159    # need up to 3 bytes. We may need up to 4 bytes per utf8 character, e.g. chars with macron,
160    # and for that, we need the encoding to be set to utf8mb4.
161    # To set up a MySQL db to use utf8mb4 requires configuration on the server side too.
162    # https://stackoverflow.com/questions/10957238/incorrect-string-value-when-trying-to-insert-utf-8-into-mysql-via-jdbc
163    # https://stackoverflow.com/questions/46727362/perl-mysql-utf8mb4-issue-possible-bug
164    # To set up the db for utf8mb4, therefore,
165    # the MySQL server needs to be configured for that char encoding by running the server as:
166    # mysql-5.7.23-linux-glibc2.12-x86_64/bin>./mysqld_safe --datadir=/Scratch/ak19/mysql/data --character_set_server=utf8mb4
167    # AND when connecting to the server, we can can either set mysql_enable_utf8mb4 => 1
168    # as a connection option
169    # OR we need to do both "set NAMES utf8mb4" AND "$dbh->{mysql_enable_utf8mb4} = 1;" after connecting
170    #
171    # Search results for DBI Set Names imply the "SET NAMES '<enc>'" command is mysql specific too,
172    # so setting the mysql specific option during connection above as "mysql_enable_utf8mb4 => 1"
173    # is no more objectionable. It has the advantage of cutting out the 2 extra lines of doing
174    # set NAMES '<enc>' and $dbh->{mysql_enable_utf8mb4} = 1 here.
175    # These lines may be preferred if more db_driver options are to be supported in future:
176    # then a separate method called set_db_encoding($enc) can work out what db_driver we're using
177    # and if mysql and enc=utfy, then it can do the following whereas it will issue other do stmts
178    # for other db_drivers, see https://www.perlmonks.org/?node_id=259456:
179   
180    #my $stmt = "set NAMES '" . $db_enc . "'";
181    #$dbh->do($stmt) || warn("Unable to set charset encoding at db server level to: " . $db_enc . "\n"); # tells MySQL to use UTF-8 for communication
182    #$dbh->{mysql_enable_utf8mb4} = 1; # tells DBD::mysql to decode the data
183   
184    # if we're here, then connection succeeded, store handle
185    $self->{'db_handle'} = $dbh;
186    return 1;
187}
188
189# Load the designated database, i.e. 'use <dbname>;'.
190# If the database doesn't yet exist, creates it and loads it.
191# (Don't create the collection's tables yet, though)
192# At the end it will have loaded the requested database (in MySQL: "use <db>;") on success.
193# As usual, returns success or failure value that can be evaluated in a boolean context.
194sub use_db {
195    my $self= shift (@_);
196    my ($db_name) = @_;
197    my $dbh = $self->{'db_handle'};
198    $db_name = $self->sanitize_name($db_name);
199   
200    print STDERR "Attempting to use database $db_name\n" if($self->{'verbosity'});
201   
202    # perl DBI switch database: https://www.perlmonks.org/?node_id=995434
203    # do() returns undef on error.
204    # connection succeeded, try to load our database. If that didn't work, attempt to create db
205    my $success = $dbh->do("use $db_name");
206   
207    if(!$success && $dbh->err == 1049) { # "Unknown database" error has code 1049 (mysql only?) meaning db doesn't exist yet
208
209    print STDERR "Database $db_name didn't exist, creating it along with the tables for the current collection...\n" if($self->{'verbosity'});
210   
211    # attempt to create the db and its tables
212    $self->create_db($db_name) || return 0;
213
214    print STDERR "   Created database $db_name\n" if($self->{'verbosity'} > 1);
215   
216    # once more attempt to use db, now that it exists
217    $dbh->do("use $db_name") || return 0;
218    #$dbh->do("use $db_name") or die "Error (code" . $dbh->err ."): " . $dbh->errstr . "\n";
219
220    $success = 1;
221    }
222    elsif($success) { # database existed and loaded successfully, but
223    # before proceeding check that the current collection's tables exist
224
225    print STDERR "@@@ DATABASE $db_name EXISTED\n" if($self->{'verbosity'} > 2);
226    }
227   
228    return $success; # could still return 0, if database failed to load with an error code != 1049
229}
230
231
232# We should already have done "use <database>;" if this gets called.
233# Just load this collection's metatable
234sub ensure_meta_table_exists {
235    my $self = shift (@_);
236   
237    my $tablename = $self->get_metadata_table_name();
238    if(!$self->table_exists($tablename)) {
239    #print STDERR "   Creating metadata table $tablename\n" if($self->{'verbosity'} > 1);
240    $self->create_metadata_table() || return 0;
241    } else {
242    print STDERR "@@@ Meta table exists\n" if($self->{'verbosity'} > 2);
243    }
244    return 1;
245}
246
247# We should already have done "use <database>;" if this gets called.
248# Just load this collection's metatable
249sub ensure_fulltxt_table_exists {
250    my $self = shift (@_);
251   
252    my $tablename = $self->get_fulltext_table_name();   
253    if(!$self->table_exists($tablename)) {
254    #print STDERR "   Creating fulltxt table $tablename\n" if($self->{'verbosity'} > 1);
255    $self->create_fulltext_table() || return 0;
256    } else {
257    print STDERR "@@@ Fulltxt table exists\n" if($self->{'verbosity'} > 2);
258    }
259    return 1;
260}
261
262# disconnect from db - https://metacpan.org/pod/DBI#disconnect
263# TODO: make sure to have committed or rolled back before disconnect
264# and that you've call finish() on statement handles if any fetch remnants remain
265sub disconnect_from_db {
266    my $self= shift (@_);   
267    my $dbh = $self->{'db_handle'};
268
269    # make sure any active stmt handles are finished
270    # NO: "When all the data has been fetched from a SELECT statement, the driver will automatically call finish for you. So you should not call it explicitly except when you know that you've not fetched all the data from a statement handle and the handle won't be destroyed soon."
271   
272    #$meta_sth = $self->{'metadata_prepared_insert_statement_handle'};
273    #$txt_sth = $self->{'fulltxt_prepared_insert_statement_handle'};
274    #$meta_sth->finish() if($meta_sth);
275    #$txt_sth->finish() if($txt_sth);
276
277    print STDERR "Disconnecting from database\n" if($self->{'verbosity'} > 1);
278   
279    my $rc = $dbh->disconnect or warn $dbh->errstr; # The handle is of little use after disconnecting. Possibly PrintError already prints a warning and this duplicates it?
280    return $rc;
281}
282
283sub create_db {
284    my $self= shift (@_);
285    my ($db_name) = @_;
286    my $dbh = $self->{'db_handle'};
287    $db_name = $self->sanitize_name($db_name);
288   
289    # https://stackoverflow.com/questions/5025768/how-can-i-create-a-mysql-database-from-a-perl-script
290    return $dbh->do("create database $db_name"); # do() will return undef on fail, https://metacpan.org/pod/DBI#do
291}
292
293
294sub create_metadata_table {
295    my $self= shift (@_);
296    my $dbh = $self->{'db_handle'};
297   
298    my $table_name = $self->get_metadata_table_name();
299    print STDERR "   Creating table $table_name\n" if($self->{'verbosity'} > 1);
300   
301    # If using an auto incremented primary key:
302    my $stmt = "CREATE TABLE $table_name (id INT NOT NULL AUTO_INCREMENT, did VARCHAR(63) NOT NULL, sid VARCHAR(63) NOT NULL, metaname VARCHAR(127) NOT NULL, metavalue VARCHAR(1023) NOT NULL, PRIMARY KEY(id));";
303    return $dbh->do($stmt);
304}
305
306# TODO: Investigate: https://dev.mysql.com/doc/search/?d=10&p=1&q=FULLTEXT
307# 12.9.1 Natural Language Full-Text Searches
308# to see whether we have to index the 'fulltxt' column of the 'fulltext' tables
309# or let user edit this file, or add it as another option
310sub create_fulltext_table {
311    my $self= shift (@_);
312    my $dbh = $self->{'db_handle'};
313   
314    my $table_name = $self->get_fulltext_table_name();
315    print STDERR "   Creating table $table_name\n" if($self->{'verbosity'} > 1);
316   
317    # If using an auto incremented primary key:
318    my $stmt = "CREATE TABLE $table_name (id INT NOT NULL AUTO_INCREMENT, did VARCHAR(63) NOT NULL, sid VARCHAR(63) NOT NULL, fulltxt LONGTEXT, PRIMARY KEY(id));";
319    return $dbh->do($stmt);
320
321}
322
323# "IF EXISTS is used to prevent an error from occurring if the database does not exist. ... DROP DATABASE returns the number of tables that were removed. The DROP DATABASE statement removes from the given database directory those files and directories that MySQL itself may create during normal operation.Jun 20, 2012"
324# MySQL 8.0 Reference Manual :: 13.1.22 DROP DATABASE Syntax
325# https://dev.mysql.com/doc/en/drop-database.html
326sub delete_collection_tables {
327    my $self= shift (@_);
328    my $dbh = $self->{'db_handle'};
329   
330    # drop table <tablename>
331    my $table = $self->get_metadata_table_name();
332    if($self->table_exists($table)) {
333    $dbh->do("drop table $table") || warn("@@@ Couldn't delete $table");
334    }
335    $table = $self->get_fulltext_table_name();
336    if($self->table_exists($table)) {
337    $dbh->do("drop table $table") || warn("@@@ Couldn't delete $table");
338    }
339}
340
341# Don't call this: it will delete the meta and full text tables for ALL collections in $db_name (localsite by default)!
342# This method is just here for debugging (for testing creating a database when there is none)
343sub _delete_database {
344    my $self= shift (@_);
345    my ($db_name) = @_;
346    my $dbh = $self->{'db_handle'};
347    $db_name = $self->sanitize_name($db_name);
348   
349    print STDERR "!!! Deleting database $db_name\n" if($self->{'verbosity'});
350   
351    # "drop database dbname"
352    $dbh->do("drop database $db_name") || return 0;
353
354    return 1;
355}
356
357
358########################### DB STATEMENTS ###########################
359
360# USEFUL: https://metacpan.org/pod/DBI
361# "Many methods have an optional \%attr parameter which can be used to pass information to the driver implementing the method. Except where specifically documented, the \%attr parameter can only be used to pass driver specific hints. In general, you can ignore \%attr parameters or pass it as undef."
362
363
364# https://www.guru99.com/insert-into.html
365# and https://dev.mysql.com/doc/refman/8.0/en/example-auto-increment.html
366#     for inserting multiple rows at once
367# https://www.perlmonks.org/bare/?node_id=316183
368# https://metacpan.org/pod/DBI#do
369# https://www.quora.com/What-is-the-difference-between-prepare-and-do-statements-in-Perl-while-we-make-a-connection-to-the-database-for-executing-the-query
370# https://docstore.mik.ua/orelly/linux/dbi/ch05_05.htm
371
372# https://metacpan.org/pod/DBI#performance
373# 'The q{...} style quoting used in this example avoids clashing with quotes that may be used in the SQL statement. Use the double-quote like qq{...} operator if you want to interpolate variables into the string. See "Quote and Quote-like Operators" in perlop for more details.'
374sub prepare_insert_metadata_row_stmthandle {
375    my $self = shift (@_);   
376    #my ($did, $sid, $metaname, $metavalue) = @_;
377    my $dbh = $self->{'db_handle'};
378   
379    my $tablename = $self->get_metadata_table_name();
380
381    #my $stmt = "INSERT INTO $tablename (did, sid, metaname, metavalue) VALUES ('$did', '$sid', '$metaname', '$metavalue');"; # ?, ?, ?, ?
382
383    # using qq{} since we want $tablename placeholder to be filled in
384    # returns Statement Handle object!
385    my $sth = $dbh->prepare(qq{INSERT INTO $tablename (did, sid, metaname, metavalue) VALUES (?, ?, ?, ?)}) || warn("Could not prepare insert statement for metadata table\n");
386
387    print STDERR "@@@@ Prepared meta insert statement: ".$sth->{'Statement'}."\n" if($self->{'verbosity'} > 2);
388   
389    return $sth;
390}
391
392sub prepare_insert_fulltxt_row_stmthandle {
393    my $self = shift (@_);
394    #my ($did, $sid, $fulltext) = @_;
395    my $dbh = $self->{'db_handle'};
396   
397    my $tablename = $self->get_fulltext_table_name();
398
399    #my $stmt = "INSERT INTO $tablename (did, sid, fulltxt) VALUES ('$did', '$sid', '$fulltext');"; ?, ?, ?
400
401    # using qq{} since we want $tablename placeholder to be filled in
402    # returns Statement Handle object!
403    my $sth = $dbh->prepare(qq{INSERT INTO $tablename (did, sid, fulltxt) VALUES (?, ?, ?)}) || warn("Could not prepare insert statement for fulltxt table\n");
404   
405    print STDERR "@@@@ Prepared fulltext insert statement: ".$sth->{'Statement'}."\n" if($self->{'verbosity'} > 2);
406   
407    return $sth;
408}
409
410
411## The 2 select statements used by GreenstoneSQLPlugin
412
413# Returns the statement handle that prepared and executed
414# a "SELECT * FROM <COLL>_metadata WHERE did = $oid" SQL statement.
415# Caller can call fetchrow_array() on returned statement handle, $sth
416# Have to use prepare() and execute() instead of do() since do() does
417# not allow for fetching result set thereafter:
418# do(): "This method  is typically most useful for non-SELECT statements that either cannot be prepared in advance (due to a limitation of the driver) or do not need to be executed repeatedly. It should not be used for SELECT statements because it does not return a statement handle (so you can't fetch any data)." https://metacpan.org/pod/release/TIMB/DBI-1.634_50/DBI.pm#do
419sub select_from_metatable_matching_docid {
420    my $self= shift (@_);
421    my ($oid) = @_;
422   
423    my $dbh = $self->{'db_handle'};
424    my $meta_table = $self->get_metadata_table_name();
425   
426    my $sth = $dbh->prepare(qq{SELECT * FROM $meta_table WHERE did = ?});
427    $sth->execute( $oid ); # will print msg on fail
428   
429    return $sth; # caller can call fetchrow_array() on returned statement handle, sth
430}
431
432# Returns the statement handle that prepared and executed
433# a "SELECT * FROM <COLL>_metadata WHERE did = $oid" SQL statement.
434# Caller can call fetchrow_array() on returned statement handle, $sth
435sub select_from_texttable_matching_docid {
436    my $self= shift (@_);
437    my ($oid) = @_;
438   
439    my $dbh = $self->{'db_handle'};
440    my $fulltxt_table = $self->get_fulltext_table_name();
441   
442    my $sth = $dbh->prepare(qq{SELECT * FROM $fulltxt_table WHERE did = ?});
443    $sth->execute( $oid ); # will print msg on fail
444   
445    return $sth; # caller can call fetchrow_array() on returned statement handle, sth
446}
447
448# delete all records in metatable with specified docid
449# https://www.tutorialspoint.com/mysql/mysql-delete-query.htm
450# DELETE FROM table_name [WHERE Clause]
451# see example under 'do' at https://metacpan.org/pod/release/TIMB/DBI-1.634_50/DBI.pm
452sub delete_recs_from_metatable_with_docid {
453    my $self= shift (@_);
454    my ($oid) = @_;
455   
456    my $dbh = $self->{'db_handle'};
457
458    #my $meta_table = $self->get_metadata_table_name();
459    ##my $rows_deleted =
460    #$dbh->do(qq{DELETE FROM $meta_table WHERE did = ?}, undef, $oid) or warn $dbh->errstr;
461
462    # If we do many deletes from this table,
463    # it may be more optimal to maintain a delete statement to repeatedly execute
464    my $sth = $self->{"sth_del_from_meta_table"};
465    if(!$sth) {
466    my $meta_table = $self->get_metadata_table_name();
467    $sth = $dbh->prepare(qq{DELETE FROM $meta_table WHERE did = ?});
468    $self->{"sth_del_from_meta_table"} = $sth;
469    }
470    $sth->execute( $oid ) or warn $dbh->errstr; # dbh set to print errors even without doing warn()
471}
472
473# delete all records in metatable with specified docid
474sub delete_recs_from_texttable_with_docid {
475    my $self= shift (@_);
476    my ($oid) = @_;
477   
478    my $dbh = $self->{'db_handle'};
479   
480    #my $fulltxt_table = $self->get_fulltext_table_name();
481    #$dbh->do(qq{DELETE FROM $fulltxt_table WHERE did = ?}, undef, $oid) or warn $dbh->errstr;   
482
483    # If we do many deletes from this table,
484    # it may be more optimal to maintain a delete statement to repeatedly execute
485    my $sth = $self->{"sth_del_from_fulltxt_table"};
486    if(!$sth) {
487    my $fulltxt_table = $self->get_fulltext_table_name();
488    $sth = $dbh->prepare(qq{DELETE FROM $fulltxt_table WHERE did = ?});
489    $self->{"sth_del_from_fulltxt_table"} = $sth;
490    }
491    $sth->execute( $oid ) or warn $dbh->errstr; # dbh set to print errors even without doing warn()
492}
493
494# Can call this after connection succeeded to get the database handle, dbh,
495# if any specific DB operation (SQL statement, create/delete)
496# needs to be executed that is not already provided as a method of this class.
497sub get_db_handle {
498    my $self= shift (@_);
499    return $self->{'db_handle'};
500}
501
502################ HELPER METHODS ##############
503
504# More basic helper methods
505sub get_metadata_table_name {
506    my $self= shift (@_);
507    my $table_name = $self->{'tablename_prefix'} . "_metadata";
508    return $table_name;
509}
510
511# FULLTEXT is a reserved keyword in (My)SQL. https://dev.mysql.com/doc/refman/5.5/en/keywords.html
512# So we can't name a table or any of its columns "fulltext". We use "fulltxt" instead.
513sub get_fulltext_table_name {
514    my $self= shift (@_);
515    my $table_name = $self->{'tablename_prefix'} . "_fulltxt";
516    return $table_name;
517}
518
519# Attempt to make sure the name parameter (for db or table name) is acceptable syntax
520# for the db in question, e.g. for mysql. For example, (My)SQL doesn't like tables or
521# databases with '-' (hyphens) in their names
522sub sanitize_name {
523    my $self= shift (@_);
524    my ($name) = @_;
525    $name =~ s/-/_/g;
526    return $name;
527}
528
529
530# I can get my version of table_exists to work, but it's not so ideal
531# Interesting that MySQL has non-standard command to CREATE TABLE IF NOT EXISTS and DROP TABLE IF EXISTS,
532# see https://www.perlmonks.org/bare/?node=DBI%20Recipes
533#    The page further has a table_exists function that could work with proper comparison
534# TODO Q: Couldn't get the first solution at https://www.perlmonks.org/bare/?node_id=500050 to work though
535sub table_exists {
536    my $self = shift (@_);
537    my $dbh = $self->{'db_handle'};
538    my ($table_name) = @_;
539
540    my @table_list = $dbh->tables;
541    #my $tables_str = @table_list[0];
542    foreach my $table (@table_list) {
543    return 1 if ($table =~ m/$table_name/);
544    }
545    return 0;
546}
547
5481;
Note: See TracBrowser for help on using the browser.