Staging large Moodle 1.9.6 upgrade to 2.0 P3 generates this error when the insert fails :-

Default exception handler: Error writing to database Debug: ERROR: value too long for type character varying(255)
INSERT INTO mdl_wiki_links (subwikiid,frompageid,tomissingpage) VALUES($1,$2,$3) RETURNING id
[array (
'subwikiid' => '357',
'frompageid' => '3101',
'tomissingpage' => ']]=

;             //encoding pattern of a quadrature encoder:

<br /><br />// From Here is the encoder read interrupt routine for encoders<br /><br />//the Interrupt service routine for Pin Change Interrupt 0.<br />ISR(PCINT0_vect){                     <br /> <br /> encoder0PINB = PINB & 0b00000011;  //select only PINB0,1  -  OTHER PINB and PIND digital pins are used for other applications, so do not want to include them in the comparison<br /> encoder2PINB = PINB & 0b00110000;  //select only PINB4,5<br /> <br /> if (encoder_sequence[[(encoder0+1)&3',
)]

• line 381 of /lib/dml/moodle_database.php: dml_write_exception thrown
• line 227 of /lib/dml/pgsql_native_moodle_database.php: call to moodle_database->query_end()
• line 768 of /lib/dml/pgsql_native_moodle_database.php: call to pgsql_native_moodle_database->query_end()
• line 821 of /lib/dml/pgsql_native_moodle_database.php: call to pgsql_native_moodle_database->insert_record_raw()
• line 305 of /mod/wiki/locallib.php: call to pgsql_native_moodle_database->insert_record()
• line 277 of /mod/wiki/locallib.php: call to wiki_refresh_page_links()
• line 210 of /mod/wiki/db/upgrade.php: call to wiki_refresh_cachedcontent()
• line 510 of /lib/upgradelib.php: call to xmldb_wiki_upgrade()
• line 294 of /lib/upgradelib.php: call to upgrade_plugins_modules()
• line 1275 of /lib/upgradelib.php: call to upgrade_plugins()
• line 114 of /admin/cli/upgrade.php: call to upgrade_noncore()

Upgraded successfully after running this command to increase the field size :-

alter table mdl_wiki_links alter column tomissingpage type char(1024);