OK now I see. I think this is a major bug in the code generator because it breaks documented behaviour.
In lines 8 to 12, SQlite is building records for an ephemeral "to do" table. Line 8: retrieve the value of the primary key with OPFLAG_NOCHNG set and store result in R6 Line 9: store the replacement string into R7 Line 10: retrieve hte value of the primary key without OPFLAG_NOCHNG and store result in R4 Line 11: Copy R6 to R5 <-- THIS IS WRONG, it should be copy R4 to R5 as per documentation Line 12: Make a record of R4 through R7 This sets up a later (lines 17-21) call to VUpdate with Argc=4 Argv[0] = R4 "primary key" Argv[1] = R5 "copy of unchanged NULL" instead of "copy of primary key" Argv[2] = R6 "unchanged NULL" Argv[2] = R7 "new value" And that explains the strange behaviour you noticed. -----Ursprüngliche Nachricht----- Von: sqlite-users [mailto:sqlite-users-boun...@mailinglists.sqlite.org] Im Auftrag von Kevin Martin Gesendet: Dienstag, 13. August 2019 17:47 An: SQLite mailing list <sqlite-users@mailinglists.sqlite.org> Betreff: [EXTERNAL] Re: [sqlite] Correct use of sqlite3_vtab_nochange/sqlite3_value_nochange > On 13 Aug 2019, at 14:08, Richard Hipp <d...@sqlite.org> wrote: > > I think that is correct. > Great, thanks. > But it never occurred to me that somebody might do this on the PRIMARY > KEY. I don't see any reason why it wouldn't work, though. I have a c++ interface built on top of the virtual table api which multiple modules are then built on top of, it doesn't know which columns are large/expensive, so the idea was just to use call sqlite3_vtab_nochange for all of them, which includes the primary key. > On 13 Aug 2019, at 13:00, Hick Gunter <h...@scigames.at> wrote: > > Very strange and AFAICT not documented. I would not have though that calling > sqlite3_value_nochange on argv[1] was even legal, given that it would > correspond to field number -1. Could you provide an "explain" (SQlite > bytecode program dump) of your statement? See below JSON for the explain as the table is not accessible in the command line tool. Thanks, Kev --- [ { "sql":"pragma table_info(modeloption_vt_writable);", "cols":["cid", "name", "type", "notnull", "dflt_value", "pk"], "time":0.016, "results":[ ["0", "option", "text", "1", "<Null>", "1"], ["1", "value", "text", "0", "<Null>", "0"] ] }, { "sql":"\n\nexplain update modeloption_vt_writable set value = 'v' where option='o';", "cols":["addr", "opcode", "p1", "p2", "p3", "p4", "p5", "comment"], "time":0, "results":[ ["0", "Init", "0", "25", "0", "", "00", "Start at 25"], ["1", "OpenEphemeral", "2", "4", "0", "", "00", "nColumn=4"], ["2", "VOpen", "1", "0", "0", "vtab:C3289DFC0", "00", ""], ["3", "Integer", "0", "10", "0", "", "00", "r[10]=0"], ["4", "Integer", "0", "11", "0", "", "00", "r[11]=0"], ["5", "VFilter", "1", "16", "10", "", "00", "iplan=r[10] zplan=''"], ["6", "VColumn", "1", "0", "12", "", "00", "r[12]=vcolumn(0); modeloption_vt_writable.option"], ["7", "Ne", "13", "15", "12", "(BINARY)", "52", "if r[12]!=r[13] goto 15"], ["8", "VColumn", "1", "0", "6", "", "01", "r[6]=vcolumn(0)"], ["9", "String8", "0", "7", "0", "v", "00", "r[7]='v'"], ["10", "VColumn", "1", "0", "4", "", "00", "r[4]=vcolumn(0)"], ["11", "SCopy", "6", "5", "0", "", "00", "r[5]=r[6]"], ["12", "MakeRecord", "4", "4", "8", "", "00", "r[8]=mkrec(r[4..7])"], ["13", "NewRowid", "2", "9", "0", "", "00", "r[9]=rowid"], ["14", "Insert", "2", "8", "9", "", "00", "intkey=r[9] data=r[8]"], ["15", "VNext", "1", "6", "0", "", "00", ""], ["16", "Rewind", "2", "23", "0", "", "00", ""], ["17", "Column", "2", "0", "4", "", "00", "r[4]="], ["18", "Column", "2", "1", "5", "", "00", "r[5]="], ["19", "Column", "2", "2", "6", "", "00", "r[6]="], ["20", "Column", "2", "3", "7", "", "00", "r[7]="], ["21", "VUpdate", "0", "4", "4", "vtab:C3289DFC0", "02", "data=r[4..7]"], ["22", "Next", "2", "17", "0", "", "00", ""], ["23", "Close", "2", "0", "0", "", "00", ""], ["24", "Halt", "0", "0", "0", "", "00", ""], ["25", "Transaction", "0", "1", "1", "0", "01", "usesStmtJournal=1"], ["26", "VBegin", "0", "0", "0", "vtab:C3289DFC0", "00", ""], ["27", "String8", "0", "13", "0", "o", "00", "r[13]='o'"], ["28", "Goto", "0", "1", "0", "", "00", ""] ] } ] _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users ___________________________________________ Gunter Hick | Software Engineer | Scientific Games International GmbH | Klitschgasse 2-4, A-1130 Vienna | FN 157284 a, HG Wien, DVR: 0430013 | (O) +43 1 80100 - 0 May be privileged. May be confidential. Please delete if not the addressee. _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
