On 3/12/20, Doug wrote:
>
> Something triggered me when I looked at the generated code: you use the
> contents of register 2 for the constant value each time through the loop.
> What if the select looks like this, with more than one function call in the
> coalesce? Do you handle it properly?
>
> S
, abs(0), abs(1), abs(2)) FROM t1;
Just curious...
Doug
> -Original Message-
> From: sqlite-users
> On Behalf Of Richard Hipp
> Sent: Thursday, March 12, 2020 7:41 AM
> To: SQLite mailing list
> Subject: Re: [sqlite] [EXTERNAL] Re: COALESCE() does not short-
> circui
On 3/12/20, Doug wrote:
> Richard, what does the explain look like with your code change, please.
Test case:
CREATE TABLE t1(a);
explain SELECT coalesce(a, abs(-9223372036854775808)) FROM t1;
Before the change:
addr opcode p1p2p3p4 p5 comment
---
Richard, what does the explain look like with your code change, please.
Doug
> -Original Message-
> From: sqlite-users
> On Behalf Of Richard Hipp
> Sent: Thursday, March 12, 2020 3:09 AM
> To: SQLite mailing list
> Subject: Re: [sqlite] [EXTERNAL] Re: COALESC
On 3/12/20, Hick Gunter wrote:
> Exactly what I gained from the EXPLAIN output.
>
> The SQL "compiler" is extracting the constant expression ABS(...) and
> evaluating it in the program prolog (where schema is checked and locks
> taken). See instructions 11 and 12
Exactly. SQLite tries to factor
Exactly what I gained from the EXPLAIN output.
The SQL "compiler" is extracting the constant expression ABS(...) and
evaluating it in the program prolog (where schema is checked and locks taken).
See instructions 11 and 12
asql> explain select coalesce((SELECT 'hello'),ABS(-9223372036854775808)
> I have a patch to fix the problem on a branch
> (https://www.sqlite.org/src/timeline?r=do-not-factor-functions) which
> you can experiment with. More changes and analysis are needed prior to
> landing on trunk. I cannot guarantee that such a landing will in fact
> occur, though it seems more lik
I recently tried using Coalesce() to check existence of a column name.
SELECT DISTINCT COALESCE((SELECT 'AColumnThatDoesNotExist' FROM TD), -999)
FROM TD;
But, the SQL error code dominates? "no such column: AColumnThatDoesNotExist"
Had to resort to:
SELECT name FROM pragma_table_info('TD') WHERE na
On 3/11/20, Hick Gunter wrote:
> While ORACLE does state that COALESCE will short circuit,
A similar problem was reported on a ticket here:
https://www.sqlite.org/src/tktview?name=3c9eadd2a6 (The problem
reported on that ticket might not seem to be the same at first glance,
but deep down they ar
While ORACLE does state that COALESCE will short circuit, SQLite does not.
May I suggest implementing your own user defined function to do this instead.
void THROW_IF_NULL(
sqlite3_context *ctx,
int argc,
sqlite3_value**argv) {
int ii;
for( ii == 0; ii < argc; ii++)
{
It is possible to infer, from the EXPLAIN output, that the SQLite program
generator attempts to isolate constant expressions and evaluates them first,
before it enters the COALESCE loop.
From my experience in reading SQL Programs, the general structure is
GOTO INIT
START:
- load constant values
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