Log Message:
sqlite3: updated to 3.21.0

Release 3.21.0:

Take advantage of the atomic-write capabilities in the F2FS filesystem when \ 
available, for greatly reduced transaction overhead. This currently requires the \ 
SQLITE_ENABLE_BATCH_ATOMIC_WRITE compile-time option.
Allow ATTACH and DETACH commands to work inside of a transaction.
Allow WITHOUT ROWID virtual tables to be writable if the PRIMARY KEY contains \ 
exactly one column.
The "fsync()" that occurs after the header is written in a WAL reset \ 
now uses the sync settings for checkpoints. This means it will use a \ 
"fullfsync" on macs if PRAGMA checkpoint_fullfsync set on.
The sqlite3_sourceid() function tries to detect if the source code has been \ 
modified from what is checked into version control and if there are \ 
modifications, the last four characters of the version hash are shown as \ 
"alt1" or "alt2". The objective is to detect accidental \ 
and/or careless edits. A forger can subvert this feature.
Improved de-quoting of column names for CREATE TABLE AS statements with an \ 
aggregate query on the right-hand side.
Fewer "stat()" system calls issued by the unix VFS.
Enhanced the LIKE optimization so that it works with an ESCAPE clause.
Enhanced PRAGMA integrity_check and PRAGMA quick_check to detect obscure row \ 
corruption that they were formerly missing. Also update both pragmas so that \ 
they return error text rather than SQLITE_CORRUPT when encountering corruption \ 
in records.
The query planner now prefers to implement FROM-clause subqueries using \ 
co-routines rather using the query flattener optimization. Support for the use \ 
of co-routines for subqueries may no longer be disabled.
Pass information about !=, IS, IS NOT, NOT NULL, and IS NULL constraints into \ 
the xBestIndex method of virtual tables.
Enhanced the CSV virtual table so that it accepts the last row of input if the \ 
final new-line character is missing.
Remove the rarely-used "scratch" memory allocator. Replace it with the \ 
SQLITE_CONFIG_SMALL_MALLOC configuration setting that gives SQLite a hint that \ 
large memory allocations should be avoided when possible.
Added the swarm virtual table to the existing union virtual table extension.
Added the sqlite_dbpage virtual table for providing direct access to pages of \ 
the database file. The source code is built into the amalgamation and is \ 
activated using the -DSQLITE_ENABLE_DBPAGE_VTAB compile-time option.
Add a new type of fts5vocab virtual table - "instance" - that provides \ 
direct access to an FTS5 full-text index at the lowest possible level.
Remove a call to rand_s() in the Windows VFS since it was causing problems in \ 
Firefox on some older laptops.
The src/shell.c source code to the command-line shell is no longer under version \ 
control. That file is now generated as part of the build process.
Miscellaneous microoptimizations reduce CPU usage by about 2.1%.
Bug fixes