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Comment:Modify the sqlite3_stmt_readonly() interface so that it returns false for CREATE TABLE IF NOT EXISTS statements even if the table already exists and the statement is really a read-only no-op. Likewise for DROP TABLE, CREATE INDEX, and DROP INDEX. Update the documentation for sqlite3_stmt_readonly() to reflect this new behavior.
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SHA3-256: cf8eb465974e596a13df56f3efbc98e098e7b74de9af4fde9ad58312db9750e4
User & Date: drh 2021-05-13 18:24:22
Context
2021-05-14
13:32
Fix an over-length source code comment in whereexpr.c. No logic changes. (check-in: af5eb902 user: drh tags: trunk)
2021-05-13
18:24
Modify the sqlite3_stmt_readonly() interface so that it returns false for CREATE TABLE IF NOT EXISTS statements even if the table already exists and the statement is really a read-only no-op. Likewise for DROP TABLE, CREATE INDEX, and DROP INDEX. Update the documentation for sqlite3_stmt_readonly() to reflect this new behavior. (check-in: cf8eb465 user: drh tags: trunk)
13:43
The content columns of the index-btree that implements a WITHOUT ROWID table are not ordered and so the query planner should not assume they are ordered. Fix for the issue identified by forum post 6c8960f545. (check-in: c21bc5a2 user: drh tags: trunk)
Changes
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Changes to src/build.c.

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    return pTab->nNVCol + i - n;
  }else{
    /* iCol is a normal or stored column */
    return n;
  }
}
#endif

















/*
** Begin constructing a new table representation in memory.  This is
** the first of several action routines that get called in response
** to a CREATE TABLE statement.  In particular, this routine is called
** after seeing tokens "CREATE" and "TABLE" and the table name. The isTemp
** flag is true if the table should be stored in the auxiliary database







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    return pTab->nNVCol + i - n;
  }else{
    /* iCol is a normal or stored column */
    return n;
  }
}
#endif

/*
** Insert a single OP_JournalMode query opcode in order to force the
** prepared statement to return false for sqlite3_stmt_readonly().  This
** is used by CREATE TABLE IF NOT EXISTS and similar if the table already
** exists, so that the prepared statement for CREATE TABLE IF NOT EXISTS
** will return false for sqlite3_stmt_readonly() even if that statement
** is a read-only no-op.
*/
static void sqlite3ForceNotReadOnly(Parse *pParse){
  int iReg = ++pParse->nMem;
  Vdbe *v = sqlite3GetVdbe(pParse);
  if( v ){
    sqlite3VdbeAddOp3(v, OP_JournalMode, 0, iReg, PAGER_JOURNALMODE_QUERY);
  }
}

/*
** Begin constructing a new table representation in memory.  This is
** the first of several action routines that get called in response
** to a CREATE TABLE statement.  In particular, this routine is called
** after seeing tokens "CREATE" and "TABLE" and the table name. The isTemp
** flag is true if the table should be stored in the auxiliary database
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    pTable = sqlite3FindTable(db, zName, zDb);
    if( pTable ){
      if( !noErr ){
        sqlite3ErrorMsg(pParse, "table %T already exists", pName);
      }else{
        assert( !db->init.busy || CORRUPT_DB );
        sqlite3CodeVerifySchema(pParse, iDb);

      }
      goto begin_table_error;
    }
    if( sqlite3FindIndex(db, zName, zDb)!=0 ){
      sqlite3ErrorMsg(pParse, "there is already an index named %s", zName);
      goto begin_table_error;
    }







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    pTable = sqlite3FindTable(db, zName, zDb);
    if( pTable ){
      if( !noErr ){
        sqlite3ErrorMsg(pParse, "table %T already exists", pName);
      }else{
        assert( !db->init.busy || CORRUPT_DB );
        sqlite3CodeVerifySchema(pParse, iDb);
        sqlite3ForceNotReadOnly(pParse);
      }
      goto begin_table_error;
    }
    if( sqlite3FindIndex(db, zName, zDb)!=0 ){
      sqlite3ErrorMsg(pParse, "there is already an index named %s", zName);
      goto begin_table_error;
    }
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  if( sqlite3ReadSchema(pParse) ) goto exit_drop_table;
  if( noErr ) db->suppressErr++;
  assert( isView==0 || isView==LOCATE_VIEW );
  pTab = sqlite3LocateTableItem(pParse, isView, &pName->a[0]);
  if( noErr ) db->suppressErr--;

  if( pTab==0 ){

    if( noErr ) sqlite3CodeVerifyNamedSchema(pParse, pName->a[0].zDatabase);


    goto exit_drop_table;
  }
  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
  assert( iDb>=0 && iDb<db->nDb );

  /* If pTab is a virtual table, call ViewGetColumnNames() to ensure
  ** it is initialized.







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  if( sqlite3ReadSchema(pParse) ) goto exit_drop_table;
  if( noErr ) db->suppressErr++;
  assert( isView==0 || isView==LOCATE_VIEW );
  pTab = sqlite3LocateTableItem(pParse, isView, &pName->a[0]);
  if( noErr ) db->suppressErr--;

  if( pTab==0 ){
    if( noErr ){
      sqlite3CodeVerifyNamedSchema(pParse, pName->a[0].zDatabase);
      sqlite3ForceNotReadOnly(pParse);
    }
    goto exit_drop_table;
  }
  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
  assert( iDb>=0 && iDb<db->nDb );

  /* If pTab is a virtual table, call ViewGetColumnNames() to ensure
  ** it is initialized.
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      }
      if( sqlite3FindIndex(db, zName, pDb->zDbSName)!=0 ){
        if( !ifNotExist ){
          sqlite3ErrorMsg(pParse, "index %s already exists", zName);
        }else{
          assert( !db->init.busy );
          sqlite3CodeVerifySchema(pParse, iDb);

        }
        goto exit_create_index;
      }
    }
  }else{
    int n;
    Index *pLoop;







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      }
      if( sqlite3FindIndex(db, zName, pDb->zDbSName)!=0 ){
        if( !ifNotExist ){
          sqlite3ErrorMsg(pParse, "index %s already exists", zName);
        }else{
          assert( !db->init.busy );
          sqlite3CodeVerifySchema(pParse, iDb);
          sqlite3ForceNotReadOnly(pParse);
        }
        goto exit_create_index;
      }
    }
  }else{
    int n;
    Index *pLoop;
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  }
  pIndex = sqlite3FindIndex(db, pName->a[0].zName, pName->a[0].zDatabase);
  if( pIndex==0 ){
    if( !ifExists ){
      sqlite3ErrorMsg(pParse, "no such index: %S", pName->a);
    }else{
      sqlite3CodeVerifyNamedSchema(pParse, pName->a[0].zDatabase);

    }
    pParse->checkSchema = 1;
    goto exit_drop_index;
  }
  if( pIndex->idxType!=SQLITE_IDXTYPE_APPDEF ){
    sqlite3ErrorMsg(pParse, "index associated with UNIQUE "
      "or PRIMARY KEY constraint cannot be dropped", 0);







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  }
  pIndex = sqlite3FindIndex(db, pName->a[0].zName, pName->a[0].zDatabase);
  if( pIndex==0 ){
    if( !ifExists ){
      sqlite3ErrorMsg(pParse, "no such index: %S", pName->a);
    }else{
      sqlite3CodeVerifyNamedSchema(pParse, pName->a[0].zDatabase);
      sqlite3ForceNotReadOnly(pParse);
    }
    pParse->checkSchema = 1;
    goto exit_drop_index;
  }
  if( pIndex->idxType!=SQLITE_IDXTYPE_APPDEF ){
    sqlite3ErrorMsg(pParse, "index associated with UNIQUE "
      "or PRIMARY KEY constraint cannot be dropped", 0);

Changes to src/sqlite.h.in.

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** sqlite3_stmt_readonly() to return true since, while those statements
** change the configuration of a database connection, they do not make 
** changes to the content of the database files on disk.
** ^The sqlite3_stmt_readonly() interface returns true for [BEGIN] since
** [BEGIN] merely sets internal flags, but the [BEGIN|BEGIN IMMEDIATE] and
** [BEGIN|BEGIN EXCLUSIVE] commands do touch the database and so
** sqlite3_stmt_readonly() returns false for those commands.









*/
int sqlite3_stmt_readonly(sqlite3_stmt *pStmt);

/*
** CAPI3REF: Query The EXPLAIN Setting For A Prepared Statement
** METHOD: sqlite3_stmt
**







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** sqlite3_stmt_readonly() to return true since, while those statements
** change the configuration of a database connection, they do not make 
** changes to the content of the database files on disk.
** ^The sqlite3_stmt_readonly() interface returns true for [BEGIN] since
** [BEGIN] merely sets internal flags, but the [BEGIN|BEGIN IMMEDIATE] and
** [BEGIN|BEGIN EXCLUSIVE] commands do touch the database and so
** sqlite3_stmt_readonly() returns false for those commands.
**
** ^This routine returns false if there is any possibility that the
** statement might change the database file.  ^A false return does
** not guarantee that the statement will change the database file.
** ^For example, an UPDATE statement might have a WHERE clause that
** makes it a no-op, but the sqlite3_stmt_readonly() result would still
** be false.  ^Similarly, a CREATE TABLE IF NOT EXISTS statement is a
** read-only no-op if the table already exists, but 
** sqlite3_stmt_readonly() still returns false for such a statement.
*/
int sqlite3_stmt_readonly(sqlite3_stmt *pStmt);

/*
** CAPI3REF: Query The EXPLAIN Setting For A Prepared Statement
** METHOD: sqlite3_stmt
**