Differences

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--- mbbsemu:development:sqlite_database_specifications [2020/11/14 21:13] – created tuday
+++ mbbsemu:development:sqlite_database_specifications [2023/10/06 23:41] (current) – external edit 127.0.0.1
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 <markdown>
-#SQLite Database Sepcifications
+#SQLite Database Specifications
 MajorBBS & WorldGroup modules make heavy use of Btrieve databases.
@@ Line 15: / Line 15: @@
 * data_t
-# The `metadata_t` table
+# The 'metadata_t' table
 This table contains metadata information about the file, analogous to the file header in the Btrieve `.DAT` file. The schema is as follows
-`CREATE TABLE metadata_t(record_length INTEGER NOT NULL, physical_record_length INTEGER NOT NULL, page_length INTEGER NOT NULL);`
+`CREATE TABLE metadata_t(record_length INTEGER NOT NULL, physical_record_length INTEGER NOT NULL, page_length INTEGER NOT NULL, variable_length_records INTEGER NOT NULL, version INTEGER NOT NULL, acs_name STRING, acs BLOB)`
-The `record_length` field is the length of all the records stored in the database, in the `data` column in the `data_t` table.
+The `record_length` field is the length of all the records stored in the database in the `data` column in the `data_t` table. For variable length records, this is the length of the fixed portion, so every record will be at least this large and of course could be much larger.
-The `physical_record_length` is the length of each physical record in the Btrieve file, and stored for informational purposes and not used by MBBSEmu.
+The `physical_record_length` is the length of each fixed physical record in the Btrieve file, and stored for informational purposes and not used by MBBSEmu.
 The `page_length` is the length of each page in the Btrieve file, and likewise stored only for information purposes and not used by MBBSEmu.
+`variable_length_records` indicates whether the records in this database are of variable length. Each record has a minimum length of `record_length.`
+`version` specifies the schema version of this database. It is used for schema upgrades, for example if MBBSEmu has an update that changes the schema number and adds/removes database fields, MBBSEmu can examine the `version` field and automatically upgrade the database if necessary.
+`acs_name` and `acs` are related fields and contain information about the Alternate Collating Sequence. ACS is used to alter string keys in the database. The `acs` table is a byte array of size 256 which performs a simple string mapping for keys. ACS tables are often used for implementing case-insensitive string keys - for example the ACS table would map lower case characters to upper case and the engine treats the key as all upper case.
+`acs_name` and `acs` are both `null` if ACS tables are not used for the database. Otherwise `acs_name` is used for informational purposes only, and `acs` is a blob of length 256.
 ***
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 There could be multiple rows in this table depending on how many keys are in the original Btrieve database.
-# The `data_t` table
+# The 'data_t' table
-This table contains all the data/records in the database.
+This table contains all the data/records in the database, one row for each record.
 The schema is dynamic based on the key, but always contains at least the following: