8000 revert: Transform OR clauses to ANY expression · postgrespro/postgres@ff9f72c · GitHub
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    akorotkovakorotkov
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    revert: Transform OR clauses to ANY expression
    This commit reverts 72bd38c due to implementation and design issues. Reported-by: Tom Lane Discussion: https://postgr.es/m/3604469.1712628736%40sss.pgh.pa.us
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    14 files changed

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    ‎doc/src/sgml/config.sgml

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    @@ -6304,63 +6304,6 @@ SELECT * FROM parent WHERE key = 2400;
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    </listitem>
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    </varlistentry>
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    <varlistentry id="guc-or-to-any-transform-limit" xreflabel="or_to_any_transform_limit">
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    <term><varname>or_to_any_transform_limit</varname> (<type>boolean</type>)
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    <indexterm>
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    <primary><varname>or_to_any_transform_limit</varname> configuration parameter</primary>
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    </indexterm>
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    </term>
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    <listitem>
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    <para>
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    Sets the minimum length of arguments in an <literal>OR</literal>
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    expression exceeding which planner will try to lookup and group
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    multiple similar <literal>OR</literal> expressions to
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    <literal>ANY</literal> (<xref linkend="functions-comparisons-any-some"/>)
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    expressions. The grouping technique of this transformation is based
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    on the equivalence of variable sides. One side of such an expression
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    must be a constant clause, and the other must contain a variable
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    clause. The default value is <literal>5</literal>. The value of
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    <literal>-1</literal> completely disables the transformation.
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    </para>
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    <para>
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    The advantage of this <literal>OR-to-ANY</literal> transformation is
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    faster query planning and execution. In certain cases, this
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    transformation also leads to more effective plans containing
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    a single index scan instead of multiple bitmap scans. However, it
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    may also cause a planning regression when distinct
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    <literal>OR</literal> arguments are better to match to distinct indexes.
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    This may happen when they have different matching partial indexes or
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    have different distributions of other columns used in the query.
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    Generally, more groupable <literal>OR</literal> arguments mean that
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    transformation will be more likely to win than to lose.
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    </para>
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    <para>
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    For example, this query has its set of five <literal>OR</literal>
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    expressions transformed to <literal>ANY</literal> with the default
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    value of <varname>or_to_any_transform_limit</varname>. But not with
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    the increased value.
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    <programlisting>
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    # EXPLAIN SELECT * FROM tbl WHERE key = 1 OR key = 2 OR key = 3 OR key = 4 OR key = 5;
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    QUERY PLAN
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    -----------------------------------------------------
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    Seq Scan on tbl (cost=0.00..51.44 rows=64 width=4)
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    Filter: (key = ANY ('{1,2,3,4,5}'::integer[]))
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    (2 rows)
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    # SET or_to_any_transform_limit = 6;
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    SET
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    # EXPLAIN SELECT * FROM tbl WHERE key = 1 OR key = 2 OR key = 3 OR key = 4 OR key = 5;
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    QUERY PLAN
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    ---------------------------------------------------------------------------
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    Seq Scan on tbl (cost=0.00..67.38 rows=63 width=4)
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    Filter: ((key = 1) OR (key = 2) OR (key = 3) OR (key = 4) OR (key = 5))
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    (2 rows)
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    </programlisting>
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    </para>
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    </listitem>
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    </varlistentry>
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    <varlistentry id="guc-plan-cache-mode" xreflabel="plan_cache_mode">
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    <term><varname>plan_cache_mode</varname> (<type>enum</type>)
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    <indexterm>

    ‎src/backend/nodes/queryjumblefuncs.c

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    @@ -141,33 +141,6 @@ JumbleQuery(Query *query)
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    return jstate;
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    }
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    JumbleState *
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    JumbleExpr(Expr *expr, uint64 *exprId)
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    {
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    JumbleState *jstate = NULL;
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    Assert(exprId != NULL);
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    jstate = (JumbleState *) palloc(sizeof(JumbleState));
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    /* Set up workspace for query jumbling */
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    jstate->jumble = (unsigned char *) palloc(JUMBLE_SIZE);
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    jstate->jumble_len = 0;
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    jstate->clocations_buf_size = 32;
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    jstate->clocations = (LocationLen *)
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    palloc(jstate->clocations_buf_size * sizeof(LocationLen));
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    jstate->clocations_count = 0;
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    jstate->highest_extern_param_id = 0;
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    /* Compute query ID */
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    _jumbleNode(jstate, (Node *) expr);
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    *exprId = DatumGetUInt64(hash_any_extended(jstate->jumble,
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    jstate->jumble_len,
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    0));
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    return jstate;
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    }
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    /*
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    * Enables query identifier computation.
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    *

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