docs: fix DB migration, add sqlite migration helper script

docs/database_migration.md

@@ -28,13 +28,14 @@ If it succeeds, you can proceed to the next step.
 
 ## Create a dump of existing data
 
-We want to dump (almost) all existing values to some file - the exception being the `metadata` table. Be sure to stop/pause LLDAP during this step, as some
+We want to dump (almost) all existing values to some file - the exception being the `metadata` table (and sometimes
+the `sqlite_sequence` table, when it exists). Be sure to stop/pause LLDAP during this step, as some
 databases (SQLite in this example) will give an error if LLDAP is in the middle of a write. The dump should consist just INSERT
 statements. There are various ways to do this, but a simple enough way is filtering a
-whole database dump. For example:
+whole database dump. This repo contains [a script](/scripts/sqlite_dump_commands.sh) to generate SQLite commands for creating an appropriate dump:
 
 ```
-sqlite3 /path/to/lldap/config/users.db .dump | grep "^INSERT" | grep -v "^INSERT INTO metadata" > /path/to/dump.sql
+./sqlite_dump_commands.sh | sqlite3 /path/to/lldap/config/users.db > /path/to/dump.sql
 ```
 
 ## Sanitize data
@@ -56,12 +57,25 @@ sed -i -r -e "s/X'([[:xdigit:]]+'[^'])/'\\\x\\1/g" \
 
 ### To MySQL
 
-MySQL mostly cooperates, but it gets some errors if you don't escape the `groups` table. Run the
+MySQL mostly cooperates, but it gets some errors if you don't escape the `groups` table. It also uses
+backticks to escape table name instead of quotes.  Run the
 following command to wrap all table names in backticks for good measure, and wrap the inserts in
 a transaction:
 
 ```
-sed -i -r -e 's/^INSERT INTO ([a-zA-Z0-9_]+) /INSERT INTO `\1` /' \
+sed -i -r -e 's/^INSERT INTO "?([a-zA-Z0-9_]+)"?/INSERT INTO `\1`/' \
+-e '1s/^/START TRANSACTION;\n/' \
+-e '$aCOMMIT;' /path/to/dump.sql
+```
+
+### To MariaDB
+
+While MariaDB is supposed to be identical to MySQL, it doesn't support timezone offsets on DATETIME
+strings. Use the following command to remove those and perform the additional MySQL sanitization:
+
+```
+sed -i -r -e "s/([^']'[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}\.[0-9]{9})\+00:00'([^'])/\1'\2/g" \
+-e 's/^INSERT INTO "?([a-zA-Z0-9_]+)"?/INSERT INTO `\1`/' \
 -e '1s/^/START TRANSACTION;\n/' \
 -e '$aCOMMIT;' /path/to/dump.sql
 ```

scripts/sqlite_dump_commands.sh

@@ -0,0 +1,9 @@
+#! /bin/bash
+
+tables=("users" "groups" "memberships" "jwt_refresh_storage" "jwt_storage" "password_reset_tokens")
+echo ".header on"
+
+for table in ${tables[@]}; do
+    echo ".mode insert $table"
+    echo "select * from $table;"
+done