SQLite/Printable version


The current, editable version of this book is available in Wikibooks, the open-content textbooks collection, at

Permission is granted to copy, distribute, and/or modify this document under the terms of the Creative Commons Attribution-ShareAlike 3.0 License.



To do:
Rewrite/Reflow text for brevity and coherence.


Unlike client–server database management systems, the SQLite engine has no standalone processes with which the application program communicates. Instead, the SQLite library is linked in and thus becomes an integral part of the application program. The library can also be called dynamically. The application program uses SQLite's functionality through simple function calls, which reduce latency in database access: function calls within a single process are more efficient than inter-process communication. SQLite stores the entire database (definitions, tables, indices, and the data itself) as a single cross-platform file on a host machine. It implements this simple design by locking the entire database file during writing. SQLite read operations can be multitasked, though writes can only be performed sequentially.

Due to the server-less design, SQLite applications require less configuration than client-server databases. SQLite is called zero-conf[1] because it does not require service management (such as startup scripts) or access control based on GRANT and passwords. Access control is handled by means of file system permissions given to the database file itself. Databases in client-server systems use file system permissions which give access to the database files only to the daemon process.

Another implication of the serverless design is that several processes may not be able to write to the database file. In server-based databases, several writers will all connect to the same daemon, which is able to handle its locks internally. SQLite on the other hand has to rely on file-system locks. It has less knowledge of the other processes that are accessing the database at the same time. Therefore, SQLite is not the preferred choice for write-intensive deployments.[2] However, for simple queries with little concurrency, SQLite performance profits from avoiding the overhead of passing its data to another process.

SQLite uses PostgreSQL as a reference platform. “What would PostgreSQL do” is used to make sense of the SQL standard.[3][4] One major deviation is that, with the exception of primary keys, SQLite does not enforce type checking; the type of a value is dynamic and not strictly constrained by the schema (although the schema will trigger a conversion when storing, if such a conversion is potentially reversible). SQLite strives to follow Postel's Rule.[5]


D. Richard Hipp designed SQLite in the spring of 2000 while working for General Dynamics on contract with the United States Navy.[6] Hipp was designing software used aboard guided missile destroyers, which originally used HP-UX with an IBM Informix database back-end. SQLite began as a Tcl extension.[7]

The design goals of SQLite were to allow the program to be operated without installing a database management system or requiring a database administrator. Hipp based the syntax and semantics on those of PostgreSQL 6.5. In August 2000, version 1.0 of SQLite was released, with storage based on gdbm (GNU Database Manager). SQLite 2.0 replaced gdbm with a custom B-tree implementation, adding transaction capability. SQLite 3.0, partially funded by America Online, added internationalization, manifest typing, and other major improvements.

In 2011 Hipp announced his plans to add a NoSQL interface (managing documents expressed in JSON) to SQLite databases and to develop UnQLite, an embeddable document-oriented database.[8]. UnQLite was released as an independent database.[9]


SQLite implements most of the SQL-92 standard for SQL but it lacks some features. For example, it partially provides triggers, and it cannot write to views (however it provides INSTEAD OF triggers that provide this functionality). While it provides complex queries, it still has limited ALTER TABLE function, as it cannot modify or delete columns.[10]

SQLite uses an unusual type system for an SQL-compatible DBMS; instead of assigning a type to a column as in most SQL database systems, types are assigned to individual values; in language terms it is dynamically typed. Moreover, it is weakly typed in some of the same ways that Perl is: one can insert a string into an integer column (although SQLite will try to convert the string to an integer first, if the column's preferred type is integer). This adds flexibility to columns, especially when bound to a dynamically typed scripting language. However, the technique is not portable to other SQL products. A common criticism is that SQLite's type system lacks the data integrity mechanism provided by statically typed columns in other products. The SQLite web site describes a "strict affinity" mode, but this feature has not yet been added.[5] However, it can be implemented with constraints like CHECK(typeof(x)='integer').[6]

SQLite with full Unicode function is optional.[11]

Several computer processes or threads may access the same database concurrently. Several read accesses can be satisfied in parallel. A write access can only be satisfied if no other accesses are currently being serviced. Otherwise, the write access fails with an error code (or can automatically be retried until a configurable timeout expires). This concurrent access situation would change when dealing with temporary tables. This restriction is relaxed in version 3.7 when write-ahead logging (WAL) is turned on enabling concurrent reads and writes.[12]

SQLite version 3.7.4 first saw the addition of the FTS4 (full text search) module, which features enhancements over the older FTS3 module.[13] FTS4 allows users to perform full text searches on documents similar to how search engines search webpages.[14] Version 3.8.2 added support for creating tables without rowid,[15] which may provide space and performance improvements.[16] Common table expressions support was added to SQLite in version 3.8.3.[17]

In 2015, with the json1 extension[18] and new subtype interfaces, SQLite version 3.9 introduced JSON content managing.

Development and distributionEdit

SQLite's code is hosted with Fossil, a distributed version control system that is itself built upon an SQLite database.[19]

A standalone command-line program is provided in SQLite's distribution. It can be used to create a database, define tables, insert and change rows, run queries and manage an SQLite database file. It also serves as an example for writing applications that use the SQLite library.

SQLite uses automated regression testing prior to each release. Over 2 million tests are run as part of a release's verification. Starting with the August 10, 2009 release of SQLite 3.6.17, SQLite releases have 100% branch test coverage, one of the components of code coverage. The tests and test harnesses are partially public domain and partially proprietary.[20]

Notable users Edit

  • The browsers Google Chrome, Opera, Safari and the Android Browser all allow for storing information in, and retrieving it from, a SQLite database within the browser, using the Web SQL Database technology, although this is rapidly becoming deprecated (namely superseded by IndexedDB).
  • Mozilla Firefox and Mozilla Thunderbird store a variety of configuration data (bookmarks, cookies, contacts etc.) in internally managed SQLite databases. There is a third-party add-on that uses the code supporting this functionality to provide a user interface for managing arbitrary SQLite databases.[21]
  • Various web application frameworks
  • Adobe Systems uses SQLite as its file format in Adobe Photoshop Lightroom, a standard database in Adobe AIR, and internally within Adobe Reader.[7]
  • Evernote uses SQLite to store its local database repository in Windows.
  • Skype[22]
  • Apple[23] adopted it as an option in macOS's Core Data API from the original implementation in Mac OS X 10.4 onwards, and also for administration of videos and songs, and in iOS for storage of text messages on the iPhone.
  • Windows 10[24]

Programming language supportEdit

A large number of programming languages provide bindings for SQLite, including:

  • AutoIt[25]
  • various dialects of BASIC including FreeBASIC, PureBasic, RFO BASIC!, Visual Basic and Xojo
  • C
  • C#
  • C++
  • Clipper//Harbour
  • Curl
  • D
  • Elixir
  • Emacs Lisp[26]
  • F#[27]
  • Go
  • Haskell
  • Haxe
  • Java (on JVM and DVM)
  • JavaScript[28]
  • Julia
  • distributions of Lisp such as Common Lisp, newLisp, OpenLisp
  • Transcript (on LiveCode)
  • LabVIEW
  • Lua
  • Nim
  • Objective-C (on macOS and iOS)
  • OCaml
  • several flavours of Pascal including Free Pascal, Component Pascal and Delphi
  • Perl[29]
  • PHP
  • Pike
  • Python[30]
  • R
  • Racket[31]
  • Ruby[32]
  • Scheme
  • Smalltalk
  • Swift (on macOS and iOS)
  • Tcl
  • Xojo



  1. "SQLite Is A Zero-Configuration Database". SQLite.org. https://sqlite.org/zeroconf.html. Retrieved August 3, 2015. 
  2. "Appropriate Uses For SQLite". SQLite.org. https://sqlite.org/whentouse.html. Retrieved 2015-09-03. 
  3. "PGCon 2014: Clustering and VODKA". https://lwn.net/Articles/601144/. Retrieved 2017-01-06. 
  4. "PGCon2014: SQLite: Protégé of PostgreSQL". https://www.pgcon.org/2014/schedule/events/736.en.html. Retrieved 2017-01-06. 
  5. a b "SQLite: StrictMode". https://sqlite.org/src/wiki?name=StrictMode. Retrieved September 3, 2015. 
  6. a b Owens, Michael (2006). The Definitive Guide to SQLite. Apress. doi:10.1007/978-1-4302-0172-4_1. ISBN 978-1-59059-673-9. 
  7. a b "Well-Known Users Of SQLite". SQLite. https://sqlite.org/famous.html. Retrieved August 5, 2015. 
  8. "Interview: Richard Hipp on UnQL, a New Query Language for Document Databases". InfoQ. August 4, 2011. http://www.infoq.com/news/2011/08/UnQL. Retrieved October 5, 2011. 
  9. UnQLite FAQ
  10. "SQL Features That SQLite Does Not Implement". SQLite.org. January 1, 2009. https://sqlite.org/omitted.html. Retrieved October 14, 2009. 
  11. "Case-insensitive matching of Unicode characters does not work.". https://sqlite.org/faq.html#q18. Retrieved 2015-09-03. 
  12. "Write Ahead Logging in SQLite 3.7". SQLite.org. https://sqlite.org/wal.html. Retrieved September 3, 2011. "WAL provides more concurrency as readers do not block writers and a writer does not block readers. Reading and writing can proceed concurrently" 
  13. "SQLite Release 3.7.4 On 2010-12-08". SQLite.org. December 8, 2010. https://sqlite.org/releaselog/3_7_4.html. Retrieved September 3, 2015. 
  14. "SQLite FTS3 and FTS4 Extensions". SQLite.org. https://sqlite.org/fts3.html. Retrieved September 3, 2015. 
  15. "SQLite Release 3.8.2 On 2013-12-06". SQLite.org. December 6, 2013. https://sqlite.org/releaselog/3_8_2.html. Retrieved September 3, 2015. 
  16. "The WITHOUT ROWID Optimization". SQLite.org. https://sqlite.org/withoutrowid.html. Retrieved September 3, 2015. 
  17. "SQLite Release 3.8.3 On 2014-02-03". SQLite.org. February 3, 2014. https://sqlite.org/releaselog/3_8_3.html. Retrieved September 3, 2015. 
  18. https://sqlite.org/json1.html
  19. "Fossil: Fossil Performance". Fossil-scm.org. August 23, 2009. https://www.fossil-scm.org/index.html/doc/tip/www/stats.wiki. Retrieved September 12, 2009. 
  20. "How SQLite Is Tested". SQLite.org. https://sqlite.org/testing.html. Retrieved September 12, 2009. 
  21. "SQLite Manager :: Add-ons for Firefox". 2015-02-28. https://addons.mozilla.org/en-US/firefox/addon/sqlite-manager/. Retrieved 2017-01-06. 
  22. "Skype client using SQLite?". Mail-archive.com. August 28, 2007. https://www.mail-archive.com/sqlite-users%40sqlite.org/msg27326.html. Retrieved June 14, 2010. 
  23. "Show Download History List of All Files Ever Downloaded Within Mac OS X". 2012-07-12. http://osxdaily.com/2012/07/12/list-download-history-mac-os-x/. Retrieved 2017-01-06. 
  24. "SQLite databases". 2016-09-19. https://msdn.microsoft.com/en-us/windows/uwp/data-access/sqlite-databases. Retrieved 2017-01-06. 
  25. "User Defined Functions". https://www.autoitscript.com/autoit3/docs/libfunctions/SQLite%20Management.htm. Retrieved 2017-01-06. 
  26. "SQLite3 API for GNU Emacs 25+". https://github.com/pekingduck/emacs-sqlite3-api. Retrieved 2017-10-02. 
  27. "SQLProvider". https://fsprojects.github.io/SQLProvider/. Retrieved 2017-01-06. 
  28. "Google Code Archive - Long-term storage for Google Code Project Hosting". http://code.google.com/p/v8-juice/wiki/JSPDO. Retrieved 2017-01-06. 
  29. Adam Kennedy. "DBD::SQLite - Self-contained RDBMS in a DBI Driver". https://metacpan.org/module/DBD::SQLite. Retrieved 2017-01-06. 
  30. "PySqlite – The Trac Project". 2015-12-31. http://trac.edgewall.org/wiki/PySqlite. Retrieved 2017-01-06. 
  31. "Continue: Web Applications in Racket - 15 Using an SQL database". https://docs.racket-lang.org/continue/index.html#%28part._.Using_an_.S.Q.L_database%29. Retrieved 2017-02-24. 
  32. "Archived copy". Archived from the original on 2010-04-17. https://web.archive.org/web/20100417055245/http://rubyforge.org/projects/sqlite-ruby. Retrieved 2010-04-03. 


Downloading and using


All tools as well as the C-sources and HTML-documentation you need to install sqlite3 on your computer are packed together in an archiveFile on SQLite's downloadPage.

In following files vv stands for version two digits following "3." uu=update (after ".vv.") and occasionally pp (usually 00) after ".uu."

As of now (12:31, 29 March 2020 (UTC)) vv=31, uu=01, pp=00

  • Tools are stored in one or more files depending on your Operating System:




Mac OS X (x86)Edit


Universal Windows PlatformEdit

Windows Phone 8Edit

Windows RuntimeEdit



Alternative sourcesEdit

not recommended

Beta sourcesEdit

Documentation (HTML)Edit


After unzipping and moving the content of the folder(s) under a directory in your %PATH% (or $PATH) you can use the executable sqlite3 from anywhere within your computer system.


For questions, requests etcetera there is a forum.

SQL standard divergences


SQLite is dynamically typed. This means that as you fill columns the affinity depends on the content. Four data types exist except NULL: BLOB, INTEGER, REAL (aka FLOAT) and TEXT.[1]


  1. Result Values From A Query sqlite.org, SQLite C Interface, visited 7 May 2019


Before reading this you're supposed to have downloaded and unpacked in your PATH the latest version of the executable command line interface sqlite3 for your operating system.


Usage: sqlite3 [OPTIONS] FILENAME [SQL]

  • FILENAME is the name of an SQLite database. A new database is created if the file does not previously exist.
  • SQL is a dot-, SQL-command or Pragma. OPTIONS include:
  -A ARGS...           = .archive ARGS and exit
  -append              append database to end of file
  -ascii               = .mode ascii
  -bail                = .bail on
  -batch               force batch I/O
  -box                 = .mode box
  -column              = .mode column
  -cmd COMMAND         run "COMMAND" before reading stdin
  -csv                 = .mode csv
  -deserialize         open using sqlite3_deserialize()
  -echo                = .echo on
  -init FILENAME       read/process named file
  -[no]header          = .header [off] or on
  -help                show this message
  -html                = .mode HTML
  -interactive         force interactive I/O
  -json                = .mode json
  -line                = .mode line
  -list                = .mode list
  -lookaside SIZE N    use N entries of SIZE bytes for lookaside memory
  -markdown            = .mode markdown
  -memtrace            trace all memory allocations and (de)allocations
  -mmap N              default mmap size set to N
  -newline SEP         = .separator "|" SEP. Default: "\n"
  -nofollow            = refuse to open symbolic links to database files
  -nullvalue TEXT      = .NULLvalue TEXT. Default ""
  -pagecache SIZE N    use N slots of SIZE bytes each for page cache memory
  -quote               = .mode quote
  -readonly            open the database read-only
  -separator SEP       = .separator SEP. Default: "|"
  -stats               print memory stats before each finalize
  -table               = .mode table
  -tabs                = .mode tabs
  -version             = .version
  -vfs NAME            use NAME as the default VFS
  -zip                 open the file as a ZIP Archive


SQLite3.37 .helpScreen (a-g)
  • .archive OPT... FILE... Manage SQL archives a
  • .auth (ON,OFF) Show authorizer callbacks
  • .backup ?DB? FILE Backup DB (default "main") to FILE
  • .bail (on,off) Stop after hitting an error. Default OFF
  • .binary (on,off) Turn binary output on or off. Default OFF
  • .cd DIRECTORY Change the working DIRECTORY
  • .changes (on,off) Show number of rows changed by SQL
  • .check GLOB Fail if output since .testcase does not match
  • .clone NEWDB Clone data into NEWDB from the existing database
  • .connection (close #) Open/close auxiliary database
  • .databases Show names and files of attached databases
  • .dbconfig ?op? ?val? Show/change sqlite3_db_config() options
  • .dbinfo ?DB? Show status information about the database
  • .dump ?TABLE? ... Dump the database in an SQL text formatt
  • .echo (on,off) Turn command echo on or off
  • .eqp (on,off,trigger,full) En-/disable automatic EXPLAIN QUERY PLAN
  • .excel Display the output of next command in a spreadsheet
  • .exit ?CODE? Exit (=.q) this program (returning CODE)
  • .expert EXPERIMENTAL. Indexes for spec. queries
  • .explain (on,off,auto) Explain format def. auto
  • .filectrl CMD ... Run sqlite3_file_control() operationsf
  • .fullschema ?--indent? Show schema and the content of sqlite_stat tables
  • .headers (on,off) Turn display of headers on or off
  • .help ?REGEX? Show this message (or only REGEX)h
  • .import OPT... FILE TABLE Import FILE > TABLE i
  • .imposter INDEX TABLE Create imposter table TABLE on index INDEX
  • .indexes ?TABLE? Show names of all indexest
  • .limit ?LIMIT? ?VAL? Display or change the value of an SQLITE_LIMIT
  • .lint OPTIONS Report potential schema issues.
  • .load FILE ?ENTRY? Load an extension library
  • .log (FILE,off) Turn logging on or off. FILE can be stderr/stdout
  • .mode MODE ?TABLE? Set output modem for tablet
  • .nullvalue STRING Use STRING in place of NULL values
  • .nonce STRING disable safe mode for one command
  • .once (-e,-x,FILE) Output for the next SQL command only to FILEe
  • .open ?OPTIONS? ?FILE? Close existing database and reopen FILEo
  • .output ?FILE? Send output to FILE or stdout
  • .parameter CMD ... Manage SQL parameter bindingsp
  • .print STRING... Print literal STRING
  • .progress N Invoke progress handler after every N opcodes
  • .prompt MAIN CONTINUE Replace the standard prompts
  • .quit Quit (=.ex) this program
------ screenshot from: ------
  • .read FILENAME Execute SQL in FILENAME
  • .recover Recover data from corrupt db
  • .restore ?DB? FILE DB content (dflt "main") from FILE
  • .save FILE Write in-memory database into FILE
  • .scanstats (on,off) sqlite3_stmt_scanstatus() metrics
  • .schema ?PATTERN? Show the CREATE statements matching PATTERNs1
  • .selftest ?--init? Run tests defined in the SELFTEST table
  • .separator COL ?ROW? Change separator for column and optionally rows2
  • .sha3sum ?OPTIONS...? Compute a SHA3 hash of database content
  • .shell CMD ARGS... Run CMD ARGS... in OS shell (=sy)
  • .show Show the current values for various settings
  • .stats (on,off) Show stats or turn stats on or off
  • .system CMD ARGS... Run CMD ARGS... in OS shell (=.sh)
  • .tables ?TABLE? List names of tablest1
  • .testcase NAME Begin redirecting output to 'testcase-out.txt'
  • .testctrl CMD ... Run sqlite3_test_control() opst2
  • .timeout MS Try opening locked tables for MS milliseconds
  • .timer (on,off) Turn SQL timer on or off
  • .trace (FILE,off) Output each SQL statement as it is run
  • .version Show detailed SQLite version info
  • .vfsinfo ?AUX? Information about the top-level VFS
  • .vfslist List all available VFSes
  • .vfsname' ?AUX? Print the name of the VFS stack
  • .width NUM1 ... Set col widths for "column" modew

More info @sqlite.org/cli.html#special_commands_to_sqlite3_dot_commands_

a .ar [OPTION...] [FILE...] The .ar command manages sqlar archives.


 .ar -cf archive.sar foo bar    # Create archive.sar from files foo and bar
 .ar -tf archive.sar            # List members of archive.sar
 .ar -xvf archive.sar           # Verbosely extract files from archive.sar

Each command line must feature exactly one command option:

 -c, --create               Create a new archive
 -u, --update               Update or add files to an existing archive
 -t, --list                 List contents of archive
 -x, --extract              Extract files from archive

And zero or more optional options:

 -v, --verbose              Print each filename as it is processed
 -f FILE, --file FILE       Operate on archive FILE (default is current db)
 -a FILE, --append FILE     Operate on FILE opened using the apndvfs VFS
 -C DIR, --directory DIR    Change to directory DIR to read/extract files
 -n, --dryrun               Show the SQL that would have occurred

See also: sar-support

e or invoke system text editor (-e) or spreadsheet (-x) on the output.
f CMD ... may be size_limit [LIMIT]; chunk_size SIZE;
persist_wal [BOOLEAN]; psow [BOOLEAN]; tempfilename
has_moved; lock_timeout MILLISEC
h only show commands matching REGEX e.g. p*=starting with p
i option to skip first line; --skip 1
l lintOptions: fkey-indexes Find missing foreign key indexes
m mode: ascii delimited by 0x1F and 0x1E; csv Comma-separated values;
column Left-aligned columns (See .width); html HTML <table> code;
insert SQL insert statements for TABLE; line One value per line
list delimited by "|"; quote Escape answers as for SQL
tabs Tab-separated values; tcl TCL list elements
o openOptions: --new option starts with an empty file
Other options: --readonly --append --zip
p paramCMDs:
clear       Erase all bindings
init          Initialize the TEMP table that holds bindings
list          List the current parameter bindings
set PARAMETER VALUE Given SQL parameter PARAMETER a value of VALUE
     PARAMETER should start with '$', ':', '@', or '?'
unset PARAMETER           Remove PARAMETER from the binding table
s1 schemaOption: --indent for pretty-printing
s2 separator for both the output mode and .import:
t1 If TABLE specified, only dump tables matching LIKE pattern TABLE.
t2 CMD ... may be always BOOLEAN; assert BOOLEAN; byteorder;
imposter SCHEMA ON/OFF ROOTPAGE; internal_functions BOOLEAN; localtime_fault BOOLEAN
never_corrupt BOOLEAN; optimizations DISABLE-MASK; pending_byte OFFSET; prng_reset;
prng_restore; prng_save; reserve BYTES-OF-RESERVE
w Negative values right-justify


If one wants to use one of following words as an identifier the word needs to be enclosed in two double quotes '"', backquotes '`' or '[' and ']'.[1]

  • ADD
  • ALL
  • AND
  • AS
  • ASC
  • BY
  • CASE
  • CAST
  • DESC
  • DO
  • DROP
  • EACH
  • ELSE
  • END
  • FAIL
  • FALSE[2]
  • FOR
  • FROM
  • FULL
  • GLOB
  • IF
  • IN
  • INTO
  • IS
  • JOIN
  • KEY
  • LAST
  • LEFT
  • LIKE
  • NO
  • NOT
  • NULL
  • OF
  • ON
  • OR
  • OVER
  • PLAN
  • ROW
  • ROWS
  • SET
  • TEMP
  • THEN
  • TIES
  • TO
  • TRUE[2]
  • VIEW
  • WHEN
  • WITH
K-notes and/or references
  1. SQLite Keywords more info @sqlite.org/lang_keywords.html.
  2. a b Not a keyword, but a predefined variable. Usage as identifier might be confusing.


Pragmas are special commands to show or [change] behavior of open database[schema](s)

  • Usage: PRAGMA [schema-name.]name [ = TEXT or INT ];
active pragmas (61)
  • analysis_limit
  • application_id
  • auto_vacuum
  • automatic_index
  • busy_timeout
  • cache_size
  • cache_spill
  • case_sensitive_like
  • cell_size_check
  • checkpoint_fullfsync
  • collation_list
  • compile_options
  • data_version
  • database_list
  • defer_foreign_keys
  • encoding
  • foreign_key_check
  • foreign_key_list
  • foreign_keys
  • freelist_count
  • fullfsync
  • function_list
  • hard_heap_limit
  • ignore_check_constraints
  • incremental_vacuum
  • index_info
  • index_list
  • index_xinfo
  • integrity_check
  • journal_mode
  • journal_size_limit
  • legacy_alter_table
  • legacy_file_format
  • locking_mode
  • max_page_count
  • mmap_size
  • module_list
  • optimize
  • page_count
  • page_size
  • pragma_list
  • query_only
  • quick_check
  • read_uncommitted
  • recursive_triggers
  • reverse_unordered_selects
  • schema_version
  • secure_delete
  • shrink_memory
  • soft_heap_limit
  • stats
  • synchronous
  • table_info
  • table_xinfo
  • temp_store
  • threads
  • trusted_schema
  • user_version
  • wal_autocheckpoint
  • wal_checkpoint
  • writable_schema
deprecated pragmas (7)
  • count_changes
  • data_store_directory
  • default_cache_size
  • empty_result_callbacks
  • full_column_names
  • short_column_names
  • temp_store_directory
pragmas with non-standard compile-options (5)
  • parser_trace
  • vdbe_addoptrace
  • vdbe_debug
  • vdbe_listing
  • vdbe_trace