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UltraLite works with rows in two formats: unpacked rows and packed rows.
are the uncompressed format. Each row must be unpacked before individual column values can be read or written.
are the compressed representation of the unpacked row, where each of the column values is compressed so that the entire row takes up as little memory as possible. The size of a packed row depends on the values in each column: for example, two rows can belong to the same table, but can differ significantly in their packed size. Note also that LONG BINARY and LONG VARCHAR columns are stored separate from the packed row.
UltraLite has a limitation that a packed row must fit on a database page. Since LONG BINARY and LONG VARCHAR columns are not stored with the packed row, they can exceed the page size.
It is important to understand that table definitions describe the row before the UltraLite runtime packs the data. Because the size of a packed row depends on the values in each column, you cannot readily pre-determine from the table definition whether the packed row requirement is satisfied. For this reason, UltraLite allows you to define a table where an unpacked row would not fit on a page. To know if a row fits on a page, you must try inserting or updating the row itself; if a row does not fit, UltraLite detects and reports this error.