--- loncom/interface/lonmysql.pm	2002/07/28 18:21:13	1.2
+++ loncom/interface/lonmysql.pm	2004/07/26 19:36:21	1.23
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # MySQL utility functions
 #
-# $Id: lonmysql.pm,v 1.2 2002/07/28 18:21:13 matthew Exp $
+# $Id: lonmysql.pm,v 1.23 2004/07/26 19:36:21 matthew Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -31,7 +31,25 @@ package Apache::lonmysql;
 
 use strict;
 use DBI;
-use Apache::lonnet();
+use POSIX qw(strftime mktime);
+
+my $mysqluser;
+my $mysqlpassword;
+
+sub set_mysql_user_and_password {
+    # If we are running under Apache and LONCAPA, use the LON-CAPA 
+    # user and password.  Otherwise...? ? ? ?
+    ($mysqluser,$mysqlpassword) = @_;
+    if (! defined($mysqluser) || ! defined($mysqlpassword)) {
+        if (! eval 'require Apache::lonnet();') {
+            $mysqluser = 'www';
+            $mysqlpassword = $Apache::lonnet::perlvar{'lonSqlAccess'};
+        } else {
+            $mysqluser = '';
+            $mysqlpassword = '';
+        }
+    }
+}
 
 ######################################################################
 ######################################################################
@@ -71,20 +89,19 @@ To create a table, you need a descriptio
 for &create_table for a description of what is needed.
 
  $table_id = &create_table({ 
-            columns => {
-                id => {
-                    type => 'INT',
-                    restrictions => 'NOT NULL',
-                    primary_key => 'yes',
-                    auto_inc    => 'yes'
-                    }
-                verbage => { type => 'TEXT' },
-                idx_verbage => { type => 'FULLTEXT',
-                                 target => 'verbage'
-                                 }
-            },
-            column_order => [qw/id verbage idx_verbage/]
-            });
+     id      => 'tableid',      # usually you will use the returned id
+     columns => (
+                 { name => 'id',
+                   type => 'INT',
+                   restrictions => 'NOT NULL',
+                   primary_key => 'yes',
+                   auto_inc    => 'yes'
+                   },
+                 { name => 'verbage',
+                   type => 'TEXT' },
+                 ),
+                       fulltext => [qw/verbage/],
+        });
 
 The above command will create a table with two columns, 'id' and 'verbage'.
 
@@ -94,7 +111,7 @@ The above command will create a table wi
 text string to be stored.  Depending on your intentions for this database,
 setting restrictions => 'NOT NULL' may help you avoid storing empty data.
 
-'idx_verbage' sets up the 'verbage' column for 'FULLTEXT' searching.
+the fulltext element sets up the 'verbage' column for 'FULLTEXT' searching.
 
 
 
@@ -120,10 +137,6 @@ Since the above table was created with t
 autoincrement, providing a value is unnecessary even though the column was
 marked as 'NOT NULL'.
 
-In the future an array of arrays or hashes may be supported, but currently
-the system only performs one insert at a time.  Given the nature of this 
-interface, transactions (locking of the table) are not supported.
-
 
 
 =item Retrieving rows
@@ -168,24 +181,83 @@ The following entries are allowed in the
 
 =over 4
 
-=item columns 
+=item Name
+
+Table name.
+
+=item Type            
+
+The type of table, typically MyISAM.
+
+=item Row_format
+
+Describes how rows should be stored in the table.  DYNAMIC or STATIC.
+
+=item Create_time
+
+The date of the tables creation.
+
+=item Update_time
+
+The date of the last modification of the table.
+
+=item Check_time
+
+Usually NULL. 
+
+=item Avg_row_length
+
+The average length of the rows.
 
-The columns information required by &create_table.
+=item Data_length
 
-=item column_order
+The length of the data stored in the table (bytes)
 
-Reference to an array containing the order of columns in the table.
+=item Max_data_length
 
-=item table_info
+The maximum possible size of the table (bytes).
 
-Set to the results of &get_table_info.
+=item Index_length
 
-=item row_insert_sth
+The length of the index for the table (bytes)
+
+=item Data_free
+
+I have no idea what this is.
+
+=item Comment 
+
+The comment associated with the table.
+
+=item Rows
+
+The number of rows in the table.
+
+=item Auto_increment
+
+The value of the next auto_increment field.
+
+=item Create_options
+
+I have no idea.
+
+=item Col_order
+
+an array reference which holds the order of columns in the table.
+
+=item row_insert_sth 
+
+The statement handler for row inserts.
+
+=item row_replace_sth 
 
 The statement handler for row inserts.
 
 =back
 
+Col_order and row_insert_sth are kept internally by lonmysql and are not
+part of the usual MySQL table information.
+
 =cut
 
 ##################################################
@@ -274,24 +346,20 @@ connection is established.
 ###############################
 sub connect_to_db { 
     return 1 if ($dbh);
-    if (! ($dbh = DBI->connect("DBI:mysql:loncapa","www",
-                               $Apache::lonnet::perlvar{'lonSqlAccess'},
+    if (! defined($mysqluser) || ! defined($mysqlpassword)) {
+        &set_mysql_user_and_password();
+    }
+    if (! ($dbh = DBI->connect("DBI:mysql:loncapa",$mysqluser,$mysqlpassword,
                                { RaiseError=>0,PrintError=>0}))) {
         $debugstring = "Unable to connect to loncapa database.";    
-        if ($dbh->err) {
+        if (! defined($dbh)) {
+            $debugstring = "Unable to connect to loncapa database.";
+            $errorstring = "dbh was undefined.";
+        } elsif ($dbh->err) {
             $errorstring = "Connection error: ".$dbh->errstr;
         }
         return undef;
     }
-    # The code below will let us switch to a different database.
-    # my $db_command = "USE $db;";
-    # my $sth = $dbh->prepare($db_command);
-    # $sth->execute();
-    # if ($sth->err) {
-    #     # Unable to use the database.  Interesting...
-    #     $dbh->disconnect;
-    #     return undef;
-    # }
     $debugstring = "Successfully connected to loncapa database.";    
     return 1;
 }
@@ -300,6 +368,36 @@ sub connect_to_db {
 
 =pod
 
+=item &verify_sql_connection()
+
+Inputs: none.
+
+Returns: 0 (failure) or 1 (success)
+
+Checks to make sure the database can be connected to.  It does not
+initialize anything in the lonmysql package.
+
+=cut
+
+###############################
+sub verify_sql_connection {
+    if (! defined($mysqluser) || ! defined($mysqlpassword)) {
+        &set_mysql_user_and_password();
+    }
+    my $connection;
+    if (! ($connection = DBI->connect("DBI:mysql:loncapa",
+                                      $mysqluser,$mysqlpassword,
+                                      { RaiseError=>0,PrintError=>0}))) {
+        return 0;
+    }
+    undef($connection);
+    return 1;
+}
+
+###############################
+
+=pod
+
 =item &disconnect_from_db()
 
 Inputs: none.
@@ -319,6 +417,9 @@ sub disconnect_from_db {
         if (exists($Tables{$_}->{'row_insert_sth'})) {
             delete($Tables{$_}->{'row_insert_sth'});
         }
+        if (exists($Tables{$_}->{'row_replace_sth'})) {
+            delete($Tables{$_}->{'row_replace_sth'});
+        }
     }
     $dbh->disconnect if ($dbh);
     $debugstring = "Disconnected from database.";
@@ -334,20 +435,36 @@ sub disconnect_from_db {
 
 Input: table identifier
 
-Returns: the number of rows in the given table.
+Returns: the number of rows in the given table, undef on error.
 
 =cut
 
 ###############################
 sub number_of_rows { 
     my ($table_id) = @_;
-    # Update the table information
-    my %Table_Info = %{&get_table_info($table_id)};
-    # return the number of rows.
-    if (defined(%Table_Info)) {
-        return $Table_Info{'Rows'};
-    }
-    return undef;
+    return undef if (! defined(&connect_to_db()));
+    return undef if (! defined(&update_table_info($table_id)));
+    return $Tables{&translate_id($table_id)}->{'Rows'};
+}
+###############################
+
+=pod
+
+=item &get_dbh()
+
+Input: nothing
+
+Returns: the database handler, or undef on error.
+
+This routine allows the programmer to gain access to the database handler.
+Be careful.
+
+=cut
+
+###############################
+sub get_dbh { 
+    return undef if (! defined(&connect_to_db()));
+    return $dbh;
 }
 
 ###############################
@@ -388,14 +505,16 @@ sub get_debug {
 
 =pod
 
-=item &get_table_info($table_id)
+=item &update_table_info()
 
 Inputs: table id
 
-Returns: undef or a pointer to a hash of data about a table.
+Returns: undef on error, 1 on success.
+
+&update_table_info updates the %Tables hash with current information about
+the given table.  
 
-&get_table_info returns all of the information it can about a table in the
-form of a hash.  Currently the fields in the hash are:
+The default MySQL table status fields are:
 
    Name             Type            Row_format
    Max_data_length  Index_length    Data_free
@@ -403,14 +522,24 @@ form of a hash.  Currently the fields in
    Avg_row_length   Data_length     Comment 
    Rows             Auto_increment  Create_options
 
+Additionally, "Col_order" is updated as well.
+
 =cut
 
 ###############################
-sub get_table_info { 
+sub update_table_info { 
     my ($table_id) = @_;
+    return undef if (! defined(&connect_to_db()));
+    my $table_status = &check_table($table_id);
+    return undef if (! defined($table_status));
+    if (! $table_status) {
+        $errorstring = "table $table_id does not exist.";
+        return undef;
+    }
     my $tablename = &translate_id($table_id);
-    return undef if (! &check_table($table_id));
-    my %tableinfo;
+    #
+    # Get MySQLs table status information.
+    #
     my @tabledesc = qw/
         Name Type Row_format Rows Avg_row_length Data_length
             Max_data_length Index_length Data_free Auto_increment 
@@ -419,73 +548,167 @@ sub get_table_info {
     my $sth = $dbh->prepare($db_command);
     $sth->execute();
     if ($sth->err) {
-        # Unable to use the database.  Interesting...
         $errorstring = "$dbh ATTEMPTED:\n".$db_command."\nRESULTING ERROR:\n".
             $sth->errstr;
-        $dbh->disconnect;
+        &disconnect_from_db();
         return undef;
     }
     #
     my @info=$sth->fetchrow_array;
     for (my $i=0;$i<= $#info ; $i++) {
-        $tableinfo{$tabledesc[$i]}= $info[$i];
+        $Tables{$tablename}->{$tabledesc[$i]}= $info[$i];
+    }
+    #
+    # Determine the column order
+    #
+    $db_command = "DESCRIBE $tablename";
+    $sth = $dbh->prepare($db_command);
+    $sth->execute();
+    if ($sth->err) {
+        $errorstring = "$dbh ATTEMPTED:\n".$db_command."\nRESULTING ERROR:\n".
+            $sth->errstr;
+        &disconnect_from_db();
+        return undef;
+    }
+    my $aref=$sth->fetchall_arrayref;
+    $Tables{$tablename}->{'Col_order'}=[]; # Clear values.
+    # The values we want are the 'Field' entries, the first column.
+    for (my $i=0;$i< @$aref ; $i++) {
+        push @{$Tables{$tablename}->{'Col_order'}},$aref->[$i]->[0];
     }
     #
     $debugstring = "Retrieved table info for $tablename";
-    return \%tableinfo;
+    return 1;
+}
+###############################
+
+=pod
+
+=item &col_order()
+
+Inputs: table id
+
+Returns: array with column order
+
+=cut
+
+
+sub col_order {
+    my $table_id=shift;
+    if (&update_table_info($table_id)) {
+	return @{$Tables{$table_id}->{'Col_order'}};
+    } else {
+	return ();
+    }
 }
 
 ###############################
 
 =pod
 
-=item &create_table
+=item &create_table()
 
 Inputs: 
-    table description
+    table description, see &build_table_creation_request
+Returns:
+    undef on error, table id on success.
+
+=cut
+
+###############################
+sub create_table {
+    return undef if (!defined(&connect_to_db($dbh)));
+    my ($table_des)=@_;
+    my $request = &build_table_creation_request($table_des);
+    #
+    # Execute the request to create the table
+    #############################################
+    my $count = $dbh->do($request);
+    if (! defined($count)) {
+        $errorstring = "$dbh ATTEMPTED:\n".$request."\nRESULTING ERROR:\n".
+            $dbh->errstr();
+        return undef;
+    }
+    #
+    # Set up the internal bookkeeping
+    #############################################
+    my $table_id;
+    if (exists($table_des->{'id'})) {
+        $table_id = $table_des->{'id'};
+    } else {
+        $table_id = &get_new_table_id();
+    }
+    my $tablename = &translate_id($table_id);
+    delete($Tables{$tablename}) if (exists($Tables{$tablename}));
+    return undef if (! defined(&update_table_info($table_id)));
+    $debugstring = "Created table $tablename at time ".time.
+        " with request\n$request";
+    return $table_id;
+}
+
+###############################
 
-Input formats:
+=pod
+
+=item build_table_creation_request
+
+Input: table description
 
     table description = {
         permanent  => 'yes' or 'no',
-        columns => {
-            colA => {
-                type         => mysql type,
-                restrictions => 'NOT NULL' or empty,
-                primary_key  => 'yes' or empty,
-                auto_inc     => 'yes' or empty,
-                target       => 'colB' (only if type eq 'FULLTEXT'),
-            }
-            colB  => { .. }
-            colZ  => { .. }
-        },
-        column_order => [ colA, colB, ..., colZ],
+        columns => [
+                    { name         => 'colA',
+                      type         => mysql type,
+                      restrictions => 'NOT NULL' or empty,
+                      primary_key  => 'yes' or empty,
+                      auto_inc     => 'yes' or empty,
+                  },
+                    { name => 'colB',
+                      ...
+                  },
+                    { name => 'colC',
+                      ...
+                  },
+        ],
+        'PRIMARY KEY' => (index_col_name,...),
+         KEY => [{ name => 'idx_name', 
+                  columns => (col1,col2,..),},],
+         INDEX => [{ name => 'idx_name', 
+                    columns => (col1,col2,..),},],
+         UNIQUE => [{ index => 'yes',
+                     name => 'idx_name',
+                     columns => (col1,col2,..),},],
+         FULLTEXT => [{ index => 'yes',
+                       name => 'idx_name',
+                       columns => (col1,col2,..),},],
+
     }
 
-Returns:
-    undef on error, table id on success.
+Returns: scalar string containing mysql commands to create the table
 
 =cut
 
 ###############################
-sub create_table {
-    return undef if (!&connect_to_db($dbh));
+sub build_table_creation_request {
     my ($table_des)=@_;
     #
     # Build request to create table
     ##################################
     my @Columns;
     my $col_des;
-    my $tableid = &get_new_table_id();
-    my $tablename = &translate_id($tableid);
+    my $table_id;
+    if (exists($table_des->{'id'})) {
+        $table_id = $table_des->{'id'};
+    } else {
+        $table_id = &get_new_table_id();
+    }
+    my $tablename = &translate_id($table_id);
     my $request = "CREATE TABLE IF NOT EXISTS ".$tablename." ";
-    foreach my $column (@{$table_des->{'column_order'}}) {
+    foreach my $coldata (@{$table_des->{'columns'}}) {
+        my $column = $coldata->{'name'};
+        next if (! defined($column));
         $col_des = '';
-        my $coldata = $table_des->{'columns'}->{$column};
-        if (lc($coldata->{'type'}) eq 'fulltext') {
-            $col_des.='FULLTEXT '.$column." (".$coldata->{'target'}.")";
-            next; # Skip to the continue block and store the column data
-        } elsif (lc($coldata->{'type'}) =~ /(enum|set)/) { # 'enum' or 'set'
+        if (lc($coldata->{'type'}) =~ /(enum|set)/) { # 'enum' or 'set'
             $col_des.=$column." ".$coldata->{'type'}."('".
                 join("', '",@{$coldata->{'values'}})."')";
         } else {
@@ -501,45 +724,60 @@ sub create_table {
         if (exists($coldata->{'default'})) {
             $col_des.=" DEFAULT '".$coldata->{'default'}."'";
         }
-        $col_des.=' AUTO_INCREMENT' if (exists($coldata->{'auto_inc'}));
-        $col_des.=' PRIMARY KEY'    if (exists($coldata->{'primary_key'}));
+        $col_des.=' AUTO_INCREMENT' if (exists($coldata->{'auto_inc'}) &&
+                                        ($coldata->{'auto_inc'} eq 'yes'));
+        $col_des.=' PRIMARY KEY'    if (exists($coldata->{'primary_key'}) &&
+                                        ($coldata->{'primary_key'} eq 'yes'));
     } continue {
         # skip blank items.
         push (@Columns,$col_des) if ($col_des ne '');
     }
+    if (exists($table_des->{'PRIMARY KEY'})) {
+        push (@Columns,'PRIMARY KEY ('.join(',',@{$table_des->{'PRIMARY KEY'}})
+              .')');
+    }
+    #
+    foreach my $indextype ('KEY','INDEX') {
+        next if (!exists($table_des->{$indextype}));
+        foreach my $indexdescription (@{$table_des->{$indextype}}) {
+            my $text = $indextype.' ';
+            if (exists($indexdescription->{'name'})) {
+                $text .=$indexdescription->{'name'};
+            }
+            $text .= ' ('.join(',',@{$indexdescription->{'columns'}}).')';
+            push (@Columns,$text);
+        }
+    }
+    #
+    foreach my $indextype ('UNIQUE','FULLTEXT') {
+        next if (! exists($table_des->{$indextype}));
+        foreach my $indexdescription (@{$table_des->{$indextype}}) {
+            my $text = $indextype.' ';
+            if (exists($indexdescription->{'index'}) &&
+                $indexdescription->{'index'} eq 'yes') {
+                $text .= 'INDEX ';
+            }
+            if (exists($indexdescription->{'name'})) {
+                $text .=$indexdescription->{'name'};
+            }
+            $text .= ' ('.join(',',@{$indexdescription->{'columns'}}).')';
+            push (@Columns,$text);
+        }
+    }
+    #
     $request .= "(".join(", ",@Columns).") ";
     unless($table_des->{'permanent'} eq 'yes') {
         $request.="COMMENT = 'temporary' ";
     } 
     $request .= "TYPE=MYISAM";
-    #
-    # Execute the request to create the table
-    #############################################
-    my $count = $dbh->do($request);
-    if (! defined($count)) {
-        $errorstring = "$dbh ATTEMPTED:\n".$request."\nRESULTING ERROR:\n".
-        return undef;
-    }
-    #
-    # Set up the internal bookkeeping
-    #############################################
-    delete($Tables{$tablename}) if (exists($Tables{$tablename}));
-    my @column_order_copy = @{$table_des->{'column_order'}};
-    $Tables{$tablename} = { 
-        columns      => $table_des->{'columns'},
-        column_order => $table_des->{'column_order'},
-        table_info   => &get_table_info($tableid),
-    };
-    $debugstring = "$dbh Created table $tablename at time ".time.
-        " with request\n$request";
-    return $tableid;
+    return $request;
 }
 
 ###############################
 
 =pod
 
-=item &get_new_table_id
+=item &get_new_table_id()
 
 Used internally to prevent table name collisions.
 
@@ -548,7 +786,6 @@ Used internally to prevent table name co
 ###############################
 sub get_new_table_id {
     my $newid = 0;
-    my $name_regex = '^'.$ENV{'user.name'}.'_'.$ENV{'user.domain'}."_(\d+)\$";
     my @tables = &tables_in_db();
     foreach (@tables) {
         if (/^$ENV{'user.name'}_$ENV{'user.domain'}_(\d+)$/) {
@@ -562,23 +799,7 @@ sub get_new_table_id {
 
 =pod
 
-=item &execute_db_command
-
-Currently unimplemented
-
-=cut
-
-###############################
-sub execute_db_command {
-    my ($tablename,$command) = @_;
-    return 1;
-}
-
-###############################
-
-=pod
-
-=item &get_rows
+=item &get_rows()
 
 Inputs: $table_id,$condition
 
@@ -593,8 +814,21 @@ greater than 0 being returned.
 ###############################
 sub get_rows {
     my ($table_id,$condition) = @_;
+    return undef if (! defined(&connect_to_db()));
+    my $table_status = &check_table($table_id);
+    return undef if (! defined($table_status));
+    if (! $table_status) {
+        $errorstring = "table $table_id does not exist.";
+        return undef;
+    }
     my $tablename = &translate_id($table_id);
-    my $request = 'SELECT * FROM '.$tablename.' WHERE '.$condition;
+    my $request;
+    if (defined($condition) && $condition ne '') {
+        $request = 'SELECT * FROM '.$tablename.' WHERE '.$condition;
+    } else {
+        $request = 'SELECT * FROM '.$tablename;
+        $condition = 'no condition';
+    }
     my $sth=$dbh->prepare($request);
     $sth->execute();
     if ($sth->err) {
@@ -605,11 +839,6 @@ sub get_rows {
     }
     $debugstring = "Got rows matching $condition";
     my @Results = @{$sth->fetchall_arrayref};
-    foreach my $row (@Results) {
-        for(my $i=0;$i<@$row;$i++) {
-            $row->[$i]=&Apache::lonnet::unescape($row->[$i]);
-        }
-    }
     return @Results;
 }
 
@@ -617,7 +846,7 @@ sub get_rows {
 
 =pod
 
-=item &store_row
+=item &store_row()
 
 Inputs: table id, row data
 
@@ -628,31 +857,38 @@ returns undef on error, 1 on success.
 ###############################
 sub store_row {
     my ($table_id,$rowdata) = @_;
+    # 
+    return undef if (! defined(&connect_to_db()));
+    my $table_status = &check_table($table_id);
+    return undef if (! defined($table_status));
+    if (! $table_status) {
+        $errorstring = "table $table_id does not exist.";
+        return undef;
+    }
+    #
     my $tablename = &translate_id($table_id);
-    my $table = $Tables{$tablename};
+    #
     my $sth;
-    if (exists($table->{'row_insert_sth'})) {
-        $sth = $table->{'row_insert_sth'};
+    if (exists($Tables{$tablename}->{'row_insert_sth'})) {
+        $sth = $Tables{$tablename}->{'row_insert_sth'};
     } else {
-        # We need to build a statement handler
+        # Build the insert statement handler
+        return undef if (! defined(&update_table_info($table_id)));
         my $insert_request = 'INSERT INTO '.$tablename.' VALUES(';
-        foreach (@{$table->{'column_order'}}) {
-            # Skip the 'fulltext' columns.
-            next if (lc($table->{'columns'}->{$_}->{'type'}) eq 'fulltext');
+        foreach (@{$Tables{$tablename}->{'Col_order'}}) {
             $insert_request.="?,";
         }
         chop $insert_request;
         $insert_request.=")";
         $sth=$dbh->prepare($insert_request);
+        $Tables{$tablename}->{'row_insert_sth'}=$sth;
     }
     my @Parameters; 
     if (ref($rowdata) eq 'ARRAY') {
         @Parameters = @$rowdata;
     } elsif (ref($rowdata) eq 'HASH') {
-        foreach (@{$table->{'column_order'}}) {
-            # Is this appropriate?  Am I being presumptious? ACK!!!!!
-            next if (lc($table->{'columns'}->{$_}->{'type'}) eq 'fulltext');
-            push(@Parameters,&Apache::lonnet::escape($rowdata->{$_}));
+        foreach (@{$Tables{$tablename}->{'Col_order'}}) {
+            push(@Parameters,$rowdata->{$_});
         }
     } 
     $sth->execute(@Parameters);
@@ -665,11 +901,124 @@ sub store_row {
     return 1;
 }
 
+
+###############################
+
+=pod
+
+=item &bulk_store_rows()
+
+Inputs: table id, [columns],[[row data1].[row data2],...]
+
+returns undef on error, 1 on success.
+
+=cut
+
+###############################
+sub bulk_store_rows {
+    my ($table_id,$columns,$rows) = @_;
+    # 
+    return undef if (! defined(&connect_to_db()));
+    my $dbh = &get_dbh();
+    return undef if (! defined($dbh));
+    my $table_status = &check_table($table_id);
+    return undef if (! defined($table_status));
+    if (! $table_status) {
+        $errorstring = "table $table_id does not exist.";
+        return undef;
+    }
+    #
+    my $tablename = &translate_id($table_id);
+    #
+    my $request = 'INSERT IGNORE INTO '.$tablename.' ';
+    if (defined($columns) && ref($columns) eq 'ARRAY') {
+        $request .= join(',',@$columns).' ';
+    }
+    if (! defined($rows) || ref($rows) ne 'ARRAY') {
+        $errorstring = "no input rows given.";
+        return undef;
+    }
+    $request .= 'VALUES ';
+    foreach my $row (@$rows) {
+        # avoid doing row stuff here...
+        $request .= '('.join(',',@$row).'),';
+    }
+    $request =~ s/,$//;
+    $dbh->do($request);
+    if ($dbh->err) {
+        $errorstring = 'Attempted '.$/.$request.$/.'Got error '.$dbh->errstr();
+        return undef;
+    }
+    return 1;
+}
+
+
+###############################
+
+=pod
+
+=item &replace_row()
+
+Inputs: table id, row data
+
+returns undef on error, 1 on success.
+
+Acts like &store_row() but uses the 'REPLACE' command instead of 'INSERT'.
+
+=cut
+
+###############################
+sub replace_row {
+    my ($table_id,$rowdata) = @_;
+    # 
+    return undef if (! defined(&connect_to_db()));
+    my $table_status = &check_table($table_id);
+    return undef if (! defined($table_status));
+    if (! $table_status) {
+        $errorstring = "table $table_id does not exist.";
+        return undef;
+    }
+    #
+    my $tablename = &translate_id($table_id);
+    #
+    my $sth;
+    if (exists($Tables{$tablename}->{'row_replace_sth'})) {
+        $sth = $Tables{$tablename}->{'row_replace_sth'};
+    } else {
+        # Build the insert statement handler
+        return undef if (! defined(&update_table_info($table_id)));
+        my $replace_request = 'REPLACE INTO '.$tablename.' VALUES(';
+        foreach (@{$Tables{$tablename}->{'Col_order'}}) {
+            $replace_request.="?,";
+        }
+        chop $replace_request;
+        $replace_request.=")";
+        $sth=$dbh->prepare($replace_request);
+        $Tables{$tablename}->{'row_replace_sth'}=$sth;
+    }
+    my @Parameters; 
+    if (ref($rowdata) eq 'ARRAY') {
+        @Parameters = @$rowdata;
+    } elsif (ref($rowdata) eq 'HASH') {
+        foreach (@{$Tables{$tablename}->{'Col_order'}}) {
+            push(@Parameters,$rowdata->{$_});
+        }
+    } 
+    $sth->execute(@Parameters);
+    if ($sth->err) {
+        $errorstring = "$dbh ATTEMPTED replace @Parameters RESULTING ERROR:\n".
+            $sth->errstr;
+        return undef;
+    }
+    $debugstring = "Stored row.";    
+    return 1;
+}
+
 ###########################################
 
 =pod
 
-=item tables_in_db
+=item &tables_in_db()
 
 Returns a list containing the names of all the tables in the database.
 Returns undef on error.
@@ -678,28 +1027,30 @@ Returns undef on error.
 
 ###########################################
 sub tables_in_db {
-    return undef if (! &connect_to_db()); # bail out if we cannot connect
-    my $sth=$dbh->prepare('SHOW TABLES;');
+    return undef if (!defined(&connect_to_db()));
+    my $sth=$dbh->prepare('SHOW TABLES');
     $sth->execute();
-    if ($sth->err) {
-        $errorstring = "$dbh ATTEMPTED:\n".'SHOW TABLES'."\nRESULTING ERROR:\n".
-            $sth->errstr;
+    $sth->execute();
+    my $aref = $sth->fetchall_arrayref;
+    if ($sth->err()) {
+        $errorstring = 
+            "$dbh ATTEMPTED:\n".'fetchall_arrayref after SHOW TABLES'.
+            "\nRESULTING ERROR:\n".$sth->errstr;
         return undef;
     }
-    my $aref = $sth->fetchall_arrayref;
-    my @table_list=();
+    my @table_list;
     foreach (@$aref) {
-        push @table_list,$_->[0];
+        push(@table_list,$_->[0]);
     }
-    $debugstring = "Got list of tables in DB: @table_list";
-    return @table_list;
+    $debugstring = "Got list of tables in DB: ".join(',',@table_list);
+    return(@table_list);
 }
 
 ###########################################
 
 =pod
 
-=item &translate_id
+=item &translate_id()
 
 Used internally to translate a numeric table id into a MySQL table name.
 If the input $id contains non-numeric characters it is assumed to have 
@@ -722,7 +1073,9 @@ sub translate_id {
 
 =pod
 
-=item &check_table($id)
+=item &check_table()
+
+Input: table id
 
 Checks to see if the requested table exists.  Returns 0 (no), 1 (yes), or 
 undef (error).
@@ -732,12 +1085,13 @@ undef (error).
 ###########################################
 sub check_table {
     my $table_id = shift;
+    return undef if (!defined(&connect_to_db()));
+    #
     $table_id = &translate_id($table_id);
-    return undef if (! &connect_to_db());
     my @Table_list = &tables_in_db();
     my $result = 0;
     foreach (@Table_list) {
-        if (/^$table_id$/) {
+        if ($_ eq $table_id) {
             $result = 1;
             last;
         }
@@ -748,7 +1102,106 @@ sub check_table {
     return $result;
 }
 
+###########################################
+
+=pod
+
+=item &remove_from_table()
+
+Input: $table_id, $column, $value
+
+Returns: the number of rows deleted.  undef on error.
+
+Executes a "delete from $tableid where $column like binary '$value'".
+
+=cut
+
+###########################################
+sub remove_from_table {
+    my ($table_id,$column,$value) = @_;
+    return undef if (!defined(&connect_to_db()));
+    #
+    $table_id = &translate_id($table_id);
+    my $command = 'DELETE FROM '.$table_id.' WHERE '.$column.
+        " LIKE BINARY ".$dbh->quote($value);
+    my $sth = $dbh->prepare($command); 
+    unless ($sth->execute()) {
+        $errorstring = "ERROR on execution of ".$command."\n".$sth->errstr;
+        return undef;
+    }
+    $debugstring = $command;
+    my $rows = $sth->rows;
+    return $rows;
+}
+
+###########################################
+
+=pod
+
+=item drop_table($table_id)
+
+Issues a 'drop table if exists' command
+
+=cut
+
+###########################################
+
+sub drop_table {
+    my ($table_id) = @_;
+    return undef if (!defined(&connect_to_db()));
+    #
+    $table_id = &translate_id($table_id);
+    my $command = 'DROP TABLE IF EXISTS '.$table_id;
+    my $sth = $dbh->prepare($command); 
+    $sth->execute();
+    if ($sth->err) {
+        $errorstring = "ERROR on execution of ".$command."\n".$sth->errstr;
+        return undef;
+    }
+    $debugstring = $command;
+    delete($Tables{$table_id}); # remove any knowledge of the table
+    return 1; # if we got here there was no error, so return a 'true' value
+}
+
+
+
+
+# ---------------------------- convert 'time' format into a datetime sql format
+sub sqltime {
+    my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
+	localtime(&unsqltime($_[0]));
+    $mon++; $year+=1900;
+    return "$year-$mon-$mday $hour:$min:$sec";
+}
+
+sub maketime {
+    my %th=@_;
+    return POSIX::mktime(($th{'seconds'},$th{'minutes'},$th{'hours'},
+                          $th{'day'},$th{'month'}-1,
+                          $th{'year'}-1900,0,0,$th{'dlsav'}));
+}
+
+
+#########################################
+#
+# Retro-fixing of un-backward-compatible time format
+
+sub unsqltime {
+    my $timestamp=shift;
+    if ($timestamp=~/^(\d+)\-(\d+)\-(\d+)\s+(\d+)\:(\d+)\:(\d+)$/) {
+        $timestamp=&maketime('year'=>$1,'month'=>$2,'day'=>$3,
+                             'hours'=>$4,'minutes'=>$5,'seconds'=>$6);
+    }
+    return $timestamp;
+}
+
+
 1;
 
 __END__;
 
+=pod
+
+=back
+
+=cut