Improvements to the documentation of sqlite3_vtab_distinct(). Do not allow

sqlite3_vtab_distinct() to return 2 or 3 if the rowid column of the virtual
table is used, as doing so might lead to an incorrect answer.

FossilOrigin-Name: 08058d66d1bde4fcf8324482ee4c6c030c681383470d5076b6f75b74aac2ae29

manifest

@@ -1,5 +1,5 @@
-C JS\serror\smessage\sand\sdoc\stypos\sreported\sin\sthe\sforum.\sNo\scode\schanges.
-D 2024-05-18T15:21:45.610
+C Improvements\sto\sthe\sdocumentation\sof\ssqlite3_vtab_distinct().\s\sDo\snot\sallow\nsqlite3_vtab_distinct()\sto\sreturn\s2\sor\s3\sif\sthe\srowid\scolumn\sof\sthe\svirtual\ntable\sis\sused,\sas\sdoing\sso\smight\slead\sto\san\sincorrect\sanswer.
+D 2024-05-20T17:52:35.621
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -752,14 +752,14 @@ F src/pragma.h e690a356c18e98414d2e870ea791c1be1545a714ba623719deb63f7f226d8bb7
 F src/prepare.c d99931f45416652895e502328ca49fe782cfc4e1ebdcda13b3736d991ebf42ce
 F src/printf.c 8b250972305e14b365561be5117ed0fd364e4fd58968776df1ce64c6280b90f9
 F src/random.c 606b00941a1d7dd09c381d3279a058d771f406c5213c9932bbd93d5587be4b9c
-F src/resolve.c 6adf4bf10151bca046f3206ae8ff07dbf90b49de20bea49197f010276f5f494d
+F src/resolve.c 22f1fa3423b377c02ae78d451cfeb1c2d96dcf0389c0642cbdcd19d3bfd7ae01
 F src/rowset.c 8432130e6c344b3401a8874c3cb49fefe6873fec593294de077afea2dce5ec97
 F src/select.c 1a841c38974d45cf15a7611398479182b61ad4c187423c380741d8b1688fe607
 F src/shell.c.in 8f2406e4e8d726452e48058d117f52e86b789f47435157b0418fb06c631349b6
-F src/sqlite.h.in 32389e0d584551b300d0157881336162c14315a424cbf385c0d65eb7c2e31f7b
+F src/sqlite.h.in c71d9ef76a6d32dc7ff2d373f2e57ce09056af26c1457bcadae5358b7628c7c3
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h 3f046c04ea3595d6bfda99b781926b17e672fd6d27da2ba6d8d8fc39981dcb54
-F src/sqliteInt.h adcf1cebb6fc00fc1f1329c00bb65ac36655736080acfd2071d84aa83a104afe
+F src/sqliteInt.h 6a9fa3902c9faca2b57060e822f2afadfbf96d64c4ede81e201f0e0c42d7e4aa
 F src/sqliteLimit.h 6878ab64bdeb8c24a1d762d45635e34b96da21132179023338c93f820eee6728
 F src/status.c cb11f8589a6912af2da3bb1ec509a94dd8ef27df4d4c1a97e0bcf2309ece972b
 F src/table.c 0f141b58a16de7e2fbe81c308379e7279f4c6b50eb08efeec5892794a0ba30d1
@@ -817,7 +817,7 @@ F src/test_window.c cdae419fdcea5bad6dcd9368c685abdad6deb59e9fc8b84b153de513d394
 F src/test_wsd.c 41cadfd9d97fe8e3e4e44f61a4a8ccd6f7ca8fe9
 F src/threads.c 4ae07fa022a3dc7c5beb373cf744a85d3c5c6c3c
 F src/tokenize.c 3f703cacdab728d7741e5a6ac242006d74fe1c2754d4f03ed889d7253259bd68
-F src/treeview.c 4f9ba6c1c7c9893fc046fdb0bc1f6bdec7660122b1ae37e51fb9b64c286caafd
+F src/treeview.c 38eefdc85d2793c4059ae651a611b30eb034389fb428f69e572bbea565da6c78
 F src/trigger.c 0858f75818ed1580332db274f1032bcc5effe567cb132df5c5be8b1d800ca97f
 F src/update.c 732404a04d1737ef14bb6ec6b84f74edf28b3c102a92ae46b4855438a710efe7
 F src/upsert.c 2e60567a0e9e8520c18671b30712a88dc73534474304af94f32bb5f3ef65ac65
@@ -839,7 +839,7 @@ F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
 F src/wal.c 887fc4ca3f020ebb2e376f222069570834ac63bf50111ef0cbf3ae417048ed89
 F src/wal.h ba252daaa94f889f4b2c17c027e823d9be47ce39da1d3799886bbd51f0490452
 F src/walker.c 7c7ea0115345851c3da4e04e2e239a29983b61fb5b038b94eede6aba462640e2
-F src/where.c d235ba520b0147f60732b3bd411e119b43be33d348251edaa6e304a8ad52c511
+F src/where.c 6f02c3936d1f9a637d8d7b5ad7362371af3e4434b0ec1eb950189a83de560d59
 F src/whereInt.h 82a13766f13d1a53b05387c2e60726289ef26404bc7b9b1f7770204d97357fb8
 F src/wherecode.c f5255f49d1f42b6e7e6b0362ff3522fa88cbcaa7213e52f9374744027ecdebca
 F src/whereexpr.c 67d15caf88a1a9528283d68ff578e024cf9fe810b517bb0343e5aaf695ad97dd
@@ -2191,8 +2191,9 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P c2188da860a1debd7c5d28b223deeef15035c33c2c5aefae9d9b620b6a2b4677
-R 54dd93ee4a8dfed3331a7d693fe52477
-U stephan
-Z f16374626a15dcefe372431613b7ed3c
+P 1a073f9acfb691eebf4a8cc78a72ff47ebbb6aba4acede6755fa3faefae48f2b 6ee041d34f292b94701919f51bbb9e12bcb9e0c4f45e4c0b83f30ff328070637
+R 65c04e4dfc1793594341c544753e5e70
+T +closed 6ee041d34f292b94701919f51bbb9e12bcb9e0c4f45e4c0b83f30ff328070637
+U drh
+Z fa3617d3b707c5d55775f8d830ee0281
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-1a073f9acfb691eebf4a8cc78a72ff47ebbb6aba4acede6755fa3faefae48f2b
+08058d66d1bde4fcf8324482ee4c6c030c681383470d5076b6f75b74aac2ae29

src/resolve.c

@@ -828,8 +828,12 @@ static int lookupName(
   ** If a generated column is referenced, set bits for every column
   ** of the table.
   */
-  if( pExpr->iColumn>=0 && cnt==1 && pMatch!=0 ){
-    pMatch->colUsed |= sqlite3ExprColUsed(pExpr);
+  if( pMatch ){
+    if( pExpr->iColumn>=0 ){
+      pMatch->colUsed |= sqlite3ExprColUsed(pExpr);
+    }else{
+      pMatch->fg.rowidUsed = 1;
+    }
   }
 
   pExpr->op = eNewExprOp;

src/sqlite.h.in

@@ -9942,24 +9942,45 @@ const char *sqlite3_vtab_collation(sqlite3_index_info*,int);
 ** <li value="2"><p>
 ** ^(If the sqlite3_vtab_distinct() interface returns 2, that means
 ** that the query planner does not need the rows returned in any particular
-** order, as long as rows with the same values in all "aOrderBy" columns
-** are adjacent.)^  ^(Furthermore, only a single row for each particular
-** combination of values in the columns identified by the "aOrderBy" field
-** needs to be returned.)^  ^It is always ok for two or more rows with the same
-** values in all "aOrderBy" columns to be returned, as long as all such rows
-** are adjacent.  ^The virtual table may, if it chooses, omit extra rows
-** that have the same value for all columns identified by "aOrderBy".
-** ^However omitting the extra rows is optional.
+** order, as long as rows with the same values in all columns identified
+** by "aOrderBy" are adjacent.)^  ^(Furthermore, when two or more rows 
+** contain the same values for all columns identified by "colUsed", all but
+** one such row may optionally be omitted from the result.)^
+** The virtual table is not required to omit rows that are duplicates
+** over the "colUsed" columns, but if the virtual table can do that without
+** too much extra effort, it could potentially help the query to run faster.
 ** This mode is used for a DISTINCT query.
 ** <li value="3"><p>
-** ^(If the sqlite3_vtab_distinct() interface returns 3, that means
-** that the query planner needs only distinct rows but it does need the
-** rows to be sorted.)^ ^The virtual table implementation is free to omit
-** rows that are identical in all aOrderBy columns, if it wants to, but
-** it is not required to omit any rows.  This mode is used for queries
+** ^(If the sqlite3_vtab_distinct() interface returns 3, that means the
+** virtual table must return rows in the order defined by "aOrderBy" as
+** if the sqlite3_vtab_distinct() interface had returned 0.  However if
+** two or more rows in the result have the same values for all columns
+** identified by "colUsed", then all but one such row may optionally be
+** omitted.)^  Like when the return value is 2, the virtual table
+** is not required to omit rows that are duplicates over the "colUsed"
+** columns, but if the virtual table can do that without
+** too much extra effort, it could potentially help the query to run faster.
+** This mode is used for queries
 ** that have both DISTINCT and ORDER BY clauses.
 ** </ol>
 **
+** <p>The following table summarizes the conditions under which the
+** virtual table is allowed to set the "orderByConsumed" flag based on
+** the value returned by sqlite3_vtab_distinct().  This table is a
+** restatement of the previous four paragraphs:
+**
+** <table border=1 cellspacing=0 cellpadding=10 width="90%">
+** <tr>
+** <td valign="top">sqlite3_vtab_distinct() return value
+** <td valign="top">Rows are returned in aOrderBy order
+** <td valign="top">Rows with the same value in all aOrderBy columns are adjacent
+** <td valign="top">Duplicates over all colUsed columns may be omitted
+** <tr><td>0<td>yes<td>yes<td>no
+** <tr><td>1<td>no<td>yes<td>no
+** <tr><td>2<td>no<td>yes<td>yes
+** <tr><td>3<td>yes<td>yes<td>yes
+** </table>
+**
 ** ^For the purposes of comparing virtual table output values to see if the
 ** values are same value for sorting purposes, two NULL values are considered
 ** to be the same.  In other words, the comparison operator is "IS"

src/sqliteInt.h

@@ -3312,6 +3312,7 @@ struct SrcItem {
     unsigned isOn :1;          /* u3.pOn was once valid and non-NULL */
     unsigned isSynthUsing :1;  /* u3.pUsing is synthesized from NATURAL */
     unsigned isNestedFrom :1;  /* pSelect is a SF_NestedFrom subquery */
+    unsigned rowidUsed :1;     /* The ROWID of this table is referenced */
   } fg;
   int iCursor;      /* The VDBE cursor number used to access this table */
   union {

src/treeview.c

@@ -194,8 +194,10 @@ void sqlite3TreeViewSrcList(TreeView *pView, const SrcList *pSrc){
     x.printfFlags |= SQLITE_PRINTF_INTERNAL;
     sqlite3_str_appendf(&x, "{%d:*} %!S", pItem->iCursor, pItem);
     if( pItem->pTab ){
-      sqlite3_str_appendf(&x, " tab=%Q nCol=%d ptr=%p used=%llx",
-           pItem->pTab->zName, pItem->pTab->nCol, pItem->pTab, pItem->colUsed);
+      sqlite3_str_appendf(&x, " tab=%Q nCol=%d ptr=%p used=%llx%s",
+           pItem->pTab->zName, pItem->pTab->nCol, pItem->pTab, 
+           pItem->colUsed,
+           pItem->fg.rowidUsed ? "+rowid" : "");
     }
     if( (pItem->fg.jointype & (JT_LEFT|JT_RIGHT))==(JT_LEFT|JT_RIGHT) ){
       sqlite3_str_appendf(&x, " FULL-OUTER-JOIN");

src/where.c

@@ -1416,7 +1416,7 @@ static sqlite3_index_info *allocateIndexInfo(
     }
     if( i==n ){
       nOrderBy = n;
-      if( (pWInfo->wctrlFlags & WHERE_DISTINCTBY) ){
+      if( (pWInfo->wctrlFlags & WHERE_DISTINCTBY) && !pSrc->fg.rowidUsed ){
         eDistinct = 2 + ((pWInfo->wctrlFlags & WHERE_SORTBYGROUP)!=0);
       }else if( pWInfo->wctrlFlags & WHERE_GROUPBY ){
         eDistinct = 1;