Re: [Tarantool-patches] [PATCH v1 1/1] sql: remove OP_Realify

[Mergen Imeev <imeevma@tarantool.org>]

Hi! Thank you for review! My answer below.

On Mon, Sep 28, 2020 at 03:55:59PM +0000, Nikita Pettik wrote:
> On 26 Sep 17:15, imeevma@tarantool.org wrote:
> > This opcode was used to convert INTEGER values to REAL. It is not
> > necessary in Tarantool and may cause errors.
> 
> Add justification: what this change fixes, in which way etc.
>  
Fixed:

commit 379694944e39a3b0c33135a724f2ee246c619110
Author: Mergen Imeev <imeevma@gmail.com>
Date:   Sat Sep 26 12:43:18 2020 +0300

    sql: remove OP_Realify
    
    This opcode was used to convert INTEGER values to REAL. It is not
    necessary in Tarantool and causes errors.
    
    Due to OP_Realify two type of errors appeared:
    1) In some cases in trigger INTEGER may be converted to DOUBLE.
    For example:
    box.execute("CREATE TABLE t (i NUMBER PRIMARY KEY, n NUMBER);")
    box.execute("CREATE TRIGGER t AFTER INSERT ON t FOR EACH ROW BEGIN UPDATE t SET n = new.n; END;")
    box.execute("INSERT INTO t VALUES (1, 1);")
    box.execute("SELECT i / 2, n / 2 FROM t;")
    
    Result:
    tarantool> box.execute("SELECT i / 2, n / 2 FROM t;")
    ---
    - metadata:
      - name: COLUMN_1
        type: number
      - name: COLUMN_2
        type: number
      rows:
      - [0, 0.5]
    ...
    
    2) If SELECT uses GROUP BY then it may return DOUBLE instead of INTEGER.
    For example:
    box.execute("CREATE TABLE t (i NUMBER PRIMARY KEY, n NUMBER);")
    box.execute("INSERT INTO t VALUES (1,1);")
    box.execute("SELECT i / 2, n / 2 FROM t GROUP BY n;")
    
    Result:
    tarantool> box.execute("SELECT i / 2, n / 2 FROM t GROUP BY n;")
    ---
    - metadata:
      - name: COLUMN_1
        type: number
      - name: COLUMN_2
        type: number
      rows:
      - [0.5, 0.5]
    ...
    
    This patch removes OP_Realify, after which these errors disappear.
    
    Closes #5335


> > Closes #5335
> > ---
> > https://github.com/tarantool/tarantool/issues/5335
> > https://github.com/tarantool/tarantool/tree/imeevma/gh-5335-remove-op-realify
> > 
> > @ChangeLog
> >  - Fixed a bug with unnecessary convertion from INTEGER to DOUBLE (gh-5335).
> > 
> >  src/box/sql/delete.c                          | 12 -----
> >  src/box/sql/expr.c                            | 13 -----
> >  src/box/sql/vdbe.c                            | 17 -------
> >  ...-unnecessary-conversation-to-double.result | 51 +++++++++++++++++++
> >  ...nnecessary-conversation-to-double.test.lua | 11 ++++
> >  5 files changed, 62 insertions(+), 42 deletions(-)
> >  create mode 100644 test/sql/gh-5335-unnecessary-conversation-to-double.result
> >  create mode 100644 test/sql/gh-5335-unnecessary-conversation-to-double.test.lua
> > 
> > diff --git a/src/box/sql/delete.c b/src/box/sql/delete.c
> > index 68abd1f58..a78c68df6 100644
> > --- a/src/box/sql/delete.c
> > +++ b/src/box/sql/delete.c
> > @@ -565,18 +565,6 @@ sql_generate_index_key(struct Parse *parse, struct index *index, int cursor,
> >  		}
> >  		uint32_t tabl_col = index->def->key_def->parts[j].fieldno;
> >  		sqlVdbeAddOp3(v, OP_Column, cursor, tabl_col, reg_base + j);
> > -		/*
> > -		 * If the column type is NUMBER but the number
> > -		 * is an integer, then it might be stored in the
> > -		 * table as an integer (using a compact
> > -		 * representation) then converted to REAL by an
> > -		 * OP_Realify opcode. But we are getting
> > -		 * ready to store this value back into an index,
> > -		 * where it should be converted by to INTEGER
> > -		 * again.  So omit the OP_Realify opcode if
> > -		 * it is present
> > -		 */
> > -		sqlVdbeDeletePriorOpcode(v, OP_Realify);
> >  	}
> >  	if (reg_out != 0)
> >  		sqlVdbeAddOp3(v, OP_MakeRecord, reg_base, col_cnt, reg_out);