SQLite 3.26.0

What's new in this version:

- Optimization: When doing an UPDATE on a table with indexes on expressions, do not update the expression indexes if they do not refer to any of the columns of the table being updated
- Allow the xBestIndex() method of virtual table implementations to return SQLITE_CONSTRAINT to indicate that the proposed query plan is unusable and should not be given further consideration
- Added the SQLITE_DBCONFIG_DEFENSIVE option which disables the ability to create corrupt database files using ordinary SQL
- Added support for read-only shadow tables when the SQLITE_DBCONFIG_DEFENSIVE option is enabled
- Added the PRAGMA legacy_alter_table command, which if enabled causes the ALTER TABLE command to behave like older version of SQLite (prior to version 3.25.0) for compatibility
- Added PRAGMA table_xinfo that works just like PRAGMA table_info except that it also shows hidden columns in virtual tables
- Added the explain virtual table as a run-time loadable extension
- Add a limit counter to the query planner to prevent excessive sqlite3_prepare() times for certain pathological SQL inputs
- Added support for the sqlite3_normalized_sql() interface, when compiling with SQLITE_ENABLE_NORMALIZE
- Enhanced triggers so that they can use table-valued functions that exist in schemas other than the schema where the trigger is defined

Enhancements to the CLI:
- Improvements to the ".help" command
- The SQLITE_HISTORY environment variable, if it exists, specifies the name of the command-line editing history file
- The --deserialize option associated with opening a new database cause the database file to be read into memory and accessed using the sqlite3_deserialize() API. This simplifies running tests on a database without modifying the file on disk

Enhancements to the geopoly extension:
- Aways stores polygons using the binary format, which is faster and uses less space
- Added the geopoly_regular() function
- Added the geopoly_ccw() function

Enhancements to the session extension:
- Added the SQLITE_CHANGESETAPPLY_INVERT flag
- Added the sqlite3changeset_start_v2() interface and the SQLITE_CHANGESETSTART_INVERT flag
- Added the changesetfuzz.c test-case generator utility