ADDED   ext/rbu/rbupartial.test
Index: ext/rbu/rbupartial.test
==================================================================
--- ext/rbu/rbupartial.test
+++ ext/rbu/rbupartial.test
@@ -0,0 +1,86 @@
+# 2019 April 11
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+
+source [file join [file dirname [info script]] rbu_common.tcl]
+set ::testprefix rbupartial
+
+db close
+sqlite3_shutdown
+sqlite3_config_uri 1
+
+foreach {tn without_rowid a b c d} {
+  1 ""              a b c d
+  2 "WITHOUT ROWID" aaa bbb ccc ddd
+  3 "WITHOUT ROWID" "\"hello\"" {"one'two"}  {[c]} ddd
+  4 "WITHOUT ROWID" {`a b`} {"one'two"}  {[c c c]} ddd
+  5 "" a b c {"d""d"}
+  6 "" {'one''two'} b {"c""c"} {"d""d"}
+} {
+  eval [string map [list \
+    %WITHOUT_ROWID% $without_rowid %A% $a %B% $b %C% $c %D% $d
+  ] {
+  reset_db
+  do_execsql_test $tn.1.0 {
+    CREATE TABLE t1(%A% PRIMARY KEY, %B%, %C%, %D%) %WITHOUT_ROWID% ;
+    CREATE INDEX i1b  ON t1(%B%);
+    CREATE INDEX i1b2 ON t1(%B%) WHERE %C%<5;
+    CREATE INDEX i1b3 ON t1(%B%) WHERE %C%>=5;
+
+    CREATE INDEX i1c  ON t1(%C%);
+    CREATE INDEX i1c2 ON t1(%C%) WHERE %C% IS NULL;
+    CREATE INDEX i1c3 ON t1(%C%) WHERE %C% IS NOT NULL;
+
+    CREATE INDEX i1c4 ON t1(%C%) WHERE %D% < 'd';
+  }
+
+  do_execsql_test $tn.1.1 {
+    INSERT INTO t1 VALUES(0, NULL, NULL, 'a');
+    INSERT INTO t1 VALUES(1, 2, 3, 'b');
+    INSERT INTO t1 VALUES(4, 5, 6, 'c');
+    INSERT INTO t1 VALUES(7, 8, 9, 'd');
+  }
+
+  forcedelete rbu.db
+  do_test $tn.1.2 {
+    sqlite3 rbu rbu.db
+    rbu eval {
+      CREATE TABLE data_t1(%A%, %B%, %C%, %D%, rbu_control);
+
+      INSERT INTO data_t1 VALUES(10, 11, 12, 'e', 0);
+      INSERT INTO data_t1 VALUES(13, 14, NULL, 'f', 0);
+
+      INSERT INTO data_t1 VALUES(0, NULL, NULL, NULL, 1);
+      INSERT INTO data_t1 VALUES(4, NULL, NULL, NULL, 1);
+
+      INSERT INTO data_t1 VALUES(7, NULL, 4, NULL, '..x.');
+      INSERT INTO data_t1 VALUES(1, 10, NULL, NULL, '.xx.');
+    }
+    rbu close
+  } {}
+
+  do_test $tn.1.3 {
+    run_rbu test.db rbu.db
+    execsql { PRAGMA integrity_check }
+  } {ok}
+
+  do_execsql_test $tn.1.4 {
+    SELECT * FROM t1 ORDER BY %A%;
+  } {
+    1 10 {} b   7 8 4 d   10 11 12 e   13 14 {} f
+  }
+
+  set step 0
+  do_rbu_vacuum_test $tn.1.5 0
+  }]
+}
+
+finish_test

Index: ext/rbu/sqlite3rbu.c
==================================================================
--- ext/rbu/sqlite3rbu.c
+++ ext/rbu/sqlite3rbu.c
@@ -238,10 +238,15 @@
 ** abIndexed:
 **   If the table has no indexes on it, abIndexed is set to NULL. Otherwise,
 **   it points to an array of flags nTblCol elements in size. The flag is
 **   set for each column that is either a part of the PK or a part of an
 **   index. Or clear otherwise.
+**
+**   If there are one or more partial indexes on the table, all fields of
+**   this array set set to 1. This is because in that case, the module has
+**   no way to tell which fields will be required to add and remove entries
+**   from the partial indexes.
 **   
 */
 struct RbuObjIter {
   sqlite3_stmt *pTblIter;         /* Iterate through tables */
   sqlite3_stmt *pIdxIter;         /* Index iterator */
@@ -1248,12 +1253,16 @@
   }
 
   pIter->nIndex = 0;
   while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pList) ){
     const char *zIdx = (const char*)sqlite3_column_text(pList, 1);
+    int bPartial = sqlite3_column_int(pList, 4);
     sqlite3_stmt *pXInfo = 0;
     if( zIdx==0 ) break;
+    if( bPartial ){
+      memset(pIter->abIndexed, 0x01, sizeof(u8)*pIter->nTblCol);
+    }
     p->rc = prepareFreeAndCollectError(p->dbMain, &pXInfo, &p->zErrmsg,
         sqlite3_mprintf("PRAGMA main.index_xinfo = %Q", zIdx)
     );
     while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pXInfo) ){
       int iCid = sqlite3_column_int(pXInfo, 1);
@@ -1955,10 +1964,66 @@
 
   if( rc!=SQLITE_OK ){
     sqlite3_result_error_code(pCtx, rc);
   }
 }
+
+static char *rbuObjIterGetIndexWhere(sqlite3rbu *p, RbuObjIter *pIter){
+  sqlite3_stmt *pStmt = 0;
+  int rc = p->rc;
+  char *zRet = 0;
+
+  if( rc==SQLITE_OK ){
+    rc = prepareAndCollectError(p->dbMain, &pStmt, &p->zErrmsg,
+        "SELECT trim(sql) FROM sqlite_master WHERE type='index' AND name=?"
+    );
+  }
+  if( rc==SQLITE_OK ){
+    int rc2;
+    rc = sqlite3_bind_text(pStmt, 1, pIter->zIdx, -1, SQLITE_STATIC);
+    if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
+      const char *zSql = (const char*)sqlite3_column_text(pStmt, 0);
+      if( zSql ){
+        int nParen = 0;           /* Number of open parenthesis */
+        int i;
+        for(i=0; zSql[i]; i++){
+          char c = zSql[i];
+          if( c=='(' ){
+            nParen++;
+          }
+          else if( c==')' ){
+            nParen--;
+            if( nParen==0 ){
+              i++;
+              break;
+            }
+          }else if( c=='"' || c=='\'' || c=='`' ){
+            for(i++; 1; i++){
+              if( zSql[i]==c ){
+                if( zSql[i+1]!=c ) break;
+                i++;
+              }
+            }
+          }else if( c=='[' ){
+            for(i++; 1; i++){
+              if( zSql[i]==']' ) break;
+            }
+          }
+        }
+        if( zSql[i] ){
+          zRet = rbuStrndup(&zSql[i], &rc);
+        }
+      }
+    }
+
+    rc2 = sqlite3_finalize(pStmt);
+    if( rc==SQLITE_OK ) rc = rc2;
+  }
+
+  p->rc = rc;
+  return zRet;
+}
 
 /*
 ** Ensure that the SQLite statement handles required to update the 
 ** target database object currently indicated by the iterator passed 
 ** as the second argument are available.
@@ -1985,17 +2050,19 @@
       const char *zTbl = pIter->zTbl;
       char *zImposterCols = 0;    /* Columns for imposter table */
       char *zImposterPK = 0;      /* Primary key declaration for imposter */
       char *zWhere = 0;           /* WHERE clause on PK columns */
       char *zBind = 0;
+      char *zPart = 0;
       int nBind = 0;
 
       assert( pIter->eType!=RBU_PK_VTAB );
       zCollist = rbuObjIterGetIndexCols(
           p, pIter, &zImposterCols, &zImposterPK, &zWhere, &nBind
       );
       zBind = rbuObjIterGetBindlist(p, nBind);
+      zPart = rbuObjIterGetIndexWhere(p, pIter);
 
       /* Create the imposter table used to write to this index. */
       sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 0, 1);
       sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 1,tnum);
       rbuMPrintfExec(p, p->dbMain,
@@ -2024,32 +2091,34 @@
       /* Create the SELECT statement to read keys in sorted order */
       if( p->rc==SQLITE_OK ){
         char *zSql;
         if( rbuIsVacuum(p) ){
           zSql = sqlite3_mprintf(
-              "SELECT %s, 0 AS rbu_control FROM '%q' ORDER BY %s%s",
+              "SELECT %s, 0 AS rbu_control FROM '%q' %s ORDER BY %s%s",
               zCollist, 
               pIter->zDataTbl,
-              zCollist, zLimit
+              zPart, zCollist, zLimit
           );
         }else
 
         if( pIter->eType==RBU_PK_EXTERNAL || pIter->eType==RBU_PK_NONE ){
           zSql = sqlite3_mprintf(
-              "SELECT %s, rbu_control FROM %s.'rbu_tmp_%q' ORDER BY %s%s",
+              "SELECT %s, rbu_control FROM %s.'rbu_tmp_%q' %s ORDER BY %s%s",
               zCollist, p->zStateDb, pIter->zDataTbl,
-              zCollist, zLimit
+              zPart, zCollist, zLimit
           );
         }else{
           zSql = sqlite3_mprintf(
-              "SELECT %s, rbu_control FROM %s.'rbu_tmp_%q' "
+              "SELECT %s, rbu_control FROM %s.'rbu_tmp_%q' %s "
               "UNION ALL "
               "SELECT %s, rbu_control FROM '%q' "
-              "WHERE typeof(rbu_control)='integer' AND rbu_control!=1 "
+              "%s %s typeof(rbu_control)='integer' AND rbu_control!=1 "
               "ORDER BY %s%s",
-              zCollist, p->zStateDb, pIter->zDataTbl, 
+              zCollist, p->zStateDb, pIter->zDataTbl, zPart,
               zCollist, pIter->zDataTbl, 
+              zPart,
+              (zPart ? "AND" : "WHERE"),
               zCollist, zLimit
           );
         }
         p->rc = prepareFreeAndCollectError(p->dbRbu, &pIter->pSelect, pz, zSql);
       }
@@ -2056,10 +2125,11 @@
 
       sqlite3_free(zImposterCols);
       sqlite3_free(zImposterPK);
       sqlite3_free(zWhere);
       sqlite3_free(zBind);
+      sqlite3_free(zPart);
     }else{
       int bRbuRowid = (pIter->eType==RBU_PK_VTAB)
                     ||(pIter->eType==RBU_PK_NONE)
                     ||(pIter->eType==RBU_PK_EXTERNAL && rbuIsVacuum(p));
       const char *zTbl = pIter->zTbl;       /* Table this step applies to */