wip: add RANDOM ROWID table option

With the new RANDOM ROWID keywords, a table can explicitly
state that it wants its rowid to be generated randomly,
not consecutively, without having to previously create a sentinel
record with rowid == max(i64).

Fixes tursodatabase#12

src/build.c

@@ -2708,6 +2708,10 @@ void sqlite3EndTable(
     p->tabFlags |= TF_WithoutRowid | TF_NoVisibleRowid;
     convertToWithoutRowidTable(pParse, p);
   }
+  if( tabOpts & TF_RandomRowid ){
+    assert( (p->tabFlags & TF_WithoutRowid) == 0 );
+    p->tabFlags |= TF_RandomRowid;
+  }
   iDb = sqlite3SchemaToIndex(db, p->pSchema);
 
 #ifndef SQLITE_OMIT_CHECK

src/insert.c

@@ -818,6 +818,10 @@ void sqlite3Insert(
   ** sqlite_sequence table and store it in memory cell regAutoinc.
   */
   regAutoinc = autoIncBegin(pParse, iDb, pTab);
+  if (pTab->tabFlags & TF_RandomRowid) {
+    fprintf(stderr, "Random rowid table detected: %s\n", pTab->zName);
+    regAutoinc = 0xffffffff; // libSQL
+  }
 
   /* Allocate a block registers to hold the rowid and the values
   ** for all columns of the new row.

src/parse.y

@@ -216,6 +216,14 @@ table_option(A) ::= WITHOUT nm(X). {
     sqlite3ErrorMsg(pParse, "unknown table option: %.*s", X.n, X.z);
   }
 }
+table_option(A) ::= RANDOM nm(X). {
+  if( X.n==5 && sqlite3_strnicmp(X.z,"rowid",5)==0 ){
+    A = TF_RandomRowid;
+  }else{
+    A = 0;
+    sqlite3ErrorMsg(pParse, "unknown table option: %.*s", X.n, X.z);
+  }
+}
 table_option(A) ::= nm(X). {
   if( X.n==6 && sqlite3_strnicmp(X.z,"strict",6)==0 ){
     A = TF_Strict;
@@ -248,7 +256,7 @@ columnname(A) ::= nm(A) typetoken(Y). {sqlite3AddColumn(pParse,A,Y);}
   CONFLICT DATABASE DEFERRED DESC DETACH DO
   EACH END EXCLUSIVE EXPLAIN FAIL FOR
   IGNORE IMMEDIATE INITIALLY INSTEAD LIKE_KW MATCH NO PLAN
-  QUERY KEY OF OFFSET PRAGMA RAISE RECURSIVE RELEASE REPLACE RESTRICT ROW ROWS
+  QUERY KEY OF OFFSET PRAGMA RAISE RANDOM RECURSIVE RELEASE REPLACE RESTRICT ROW ROWS
   ROLLBACK SAVEPOINT TEMP TRIGGER VACUUM VIEW VIRTUAL WITH WITHOUT
   NULLS FIRST LAST
 %ifdef SQLITE_OMIT_COMPOUND_SELECT

src/sqliteInt.h

@@ -2341,6 +2341,8 @@ struct Table {
 #define TF_Ephemeral      0x00004000 /* An ephemeral table */
 #define TF_Eponymous      0x00008000 /* An eponymous virtual table */
 #define TF_Strict         0x00010000 /* STRICT mode */
+/* libSQL extension */
+#define TF_RandomRowid    0x01000000 /* Random rowid */
 
 /*
 ** Allowed values for Table.eTabType

src/vdbe.c

@@ -5419,6 +5419,12 @@ case OP_NewRowid: {           /* out2 */
       }
     }
 
+    if ( pOp->p3 == 0xffffffff) {
+      fprintf(stderr, "assigning random rowid\n");
+      pC->useRandomRowid = 1;
+      pOp->p3 = 0;
+    }
+
 #ifndef SQLITE_OMIT_AUTOINCREMENT
     if( pOp->p3 ){
       /* Assert that P3 is a valid memory cell. */

tool/mkkeywordhash.c

@@ -278,6 +278,7 @@ static Keyword aKeywordTable[] = {
   { "PRIMARY",          "TK_PRIMARY",      ALWAYS,           1      },
   { "QUERY",            "TK_QUERY",        EXPLAIN,          0      },
   { "RAISE",            "TK_RAISE",        TRIGGER,          1      },
+  { "RANDOM",           "TK_RANDOM",       ALWAYS,           1      },
   { "RANGE",            "TK_RANGE",        WINDOWFUNC,       3      },
   { "RECURSIVE",        "TK_RECURSIVE",    CTE,              3      },
   { "REFERENCES",       "TK_REFERENCES",   FKEY,             1      },