#Insert node basex update

If a record with pre = 12 is to be inserted, it needs to be stored in the first block, which is, however, full. The corresponding fpre's will be 0 and 256. write operation, they are kept in main memory and flushed to disk on closing the database.Ī newly created database with 256 + 10 records will occupy the first two blocks with physical addresses. Since these two maps will not grow excessively large, but are accessed resp. The physical address of each block is stored in tbli.basex, too. These will be referred as fpre from now on. The records within a block are sorted by their pre value (which, therefore, can be implicitly determined and need not be saved).įor each block BaseX stores in a separate file ( tbli.basex) the smallest pre value within that block (and since the records are sorted, that will be the pre value of the first record stored in the block). each block can have max 256 records each with length 16 bytes.

Block StorageīaseX logically splits the tbl.basex file into blocks with length 4096 bytes, i.e. If the UPDINDEX option is turned on, an additional index will be maintained to speed up the process. The db:node-pre and db:node-id functions can be called to retrieve the pre and id values of a node, and db:open-pre and db:open-id can be used to go back and retrieve the original node. If nodes are deleted or inserted somewhere else, the values will diverge, as shown in the next example: $ basex -c'create db db HiThere' -q'insert node before /xml' -c'info storage' The values will remain to be identical if new nodes are exclusively added to the end of the database. As long as no updates are performed on a database, the pre and id values are identical.

#Insert node basex update

ID ValueĮach database node has a persistent id value, which remains valid after update operations, and which is referenced by the value indexes. As a result, it will change whenever a node with a smaller pre values is added to or deleted from a database. It is actually not stored in the database instead, it is implicitly given by the table position. The pre value of a node represents the order in which the XML nodes are visited by a SAX parser. The node table of a database can be displayed via the INFO STORAGE command: $ basex -c'create db db HiThere' -c'info storage' Node TableīaseX stores all XML nodes in a flat table.

This article describes the Storage Layout of the main database table.