Re: Centralizing protective copying of utility statements

[Tom Lane]

I wrote:
> (In any case, if someone does get excited about this, they
> could rearrange things to push the copyObject calls into the
> individual arms of the switch in ProcessUtility.  Personally
> though I doubt it could be worth the code bloat.)

It occurred to me to try making the copying code look like

    if (readOnlyTree)
    {
        switch (nodeTag(parsetree))
        {
            case T_TransactionStmt:
                /* stmt is immutable anyway, no need to copy */
                break;
            default:
                pstmt = copyObject(pstmt);
                parsetree = pstmt->utilityStmt;
                break;
        }
    }

This didn't move the needle at all, in fact it seems maybe a
shade slower:

tps = 23502.288878 (without initial connection time)
tps = 23643.821923 (without initial connection time)
tps = 23082.976795 (without initial connection time)
tps = 23547.527641 (without initial connection time)

So I think this confirms my gut feeling that copyObject on a
TransactionStmt is negligible.  To the extent that the prior
measurement shows a real difference, it's probably a chance effect
of changing code layout elsewhere.

                        regards, tom lane