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[PATCH v11 5/7] Row pattern recognition patch (docs). 3+ messages / 3 participants [nested] [flat]
* [PATCH v11 5/7] Row pattern recognition patch (docs). @ 2023-11-08 06:57 Tatsuo Ishii <[email protected]> 0 siblings, 0 replies; 3+ messages in thread From: Tatsuo Ishii @ 2023-11-08 06:57 UTC (permalink / raw) --- doc/src/sgml/advanced.sgml | 80 ++++++++++++++++++++++++++++++++++++ doc/src/sgml/func.sgml | 54 ++++++++++++++++++++++++ doc/src/sgml/ref/select.sgml | 38 ++++++++++++++++- 3 files changed, 170 insertions(+), 2 deletions(-) diff --git a/doc/src/sgml/advanced.sgml b/doc/src/sgml/advanced.sgml index 755c9f1485..cf18dd887e 100644 --- a/doc/src/sgml/advanced.sgml +++ b/doc/src/sgml/advanced.sgml @@ -537,6 +537,86 @@ WHERE pos < 3; <literal>rank</literal> less than 3. </para> + <para> + Row pattern common syntax can be used to perform row pattern recognition + in a query. Row pattern common syntax includes two sub + clauses: <literal>DEFINE</literal> + and <literal>PATTERN</literal>. <literal>DEFINE</literal> defines + definition variables along with an expression. The expression must be a + logical expression, which means it must + return <literal>TRUE</literal>, <literal>FALSE</literal> + or <literal>NULL</literal>. The expression may comprise column references + and functions. Window functions, aggregate functions and subqueries are + not allowed. An example of <literal>DEFINE</literal> is as follows. + +<programlisting> +DEFINE + LOWPRICE AS price <= 100, + UP AS price > PREV(price), + DOWN AS price < PREV(price) +</programlisting> + + Note that <function>PREV</function> returns the price column in the + previous row if it's called in a context of row pattern recognition. So in + the second line the definition variable "UP" is <literal>TRUE</literal> + when the price column in the current row is greater than the price column + in the previous row. Likewise, "DOWN" is <literal>TRUE</literal> when when + the price column in the current row is lower than the price column in the + previous row. + </para> + <para> + Once <literal>DEFINE</literal> exists, <literal>PATTERN</literal> can be + used. <literal>PATTERN</literal> defines a sequence of rows that satisfies + certain conditions. For example following <literal>PATTERN</literal> + defines that a row starts with the condition "LOWPRICE", then one or more + rows satisfy "UP" and finally one or more rows satisfy "DOWN". Note that + "+" means one or more matches. Also you can use "*", which means zero or + more matches. If a sequence of rows which satisfies the PATTERN is found, + in the starting row of the sequence of rows all window functions and + aggregates are shown in the target list. Note that aggregations only look + into the matched rows, rather than whole frame. In the second or + subsequent rows all window functions and aggregates are NULL. For rows + that do not match the PATTERN, all window functions and aggregates are + shown AS NULL too, except count which shows 0. This is because the + unmatched rows are in an empty frame. Example of + a <literal>SELECT</literal> using the <literal>DEFINE</literal> + and <literal>PATTERN</literal> clause is as follows. + +<programlisting> +SELECT company, tdate, price, + first_value(price) OVER w, + max(price) OVER w, + count(price) OVER w +FROM stock, + WINDOW w AS ( + PARTITION BY company + ORDER BY tdate + ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING + AFTER MATCH SKIP PAST LAST ROW + INITIAL + PATTERN (LOWPRICE UP+ DOWN+) + DEFINE + LOWPRICE AS price <= 100, + UP AS price > PREV(price), + DOWN AS price < PREV(price) +); +</programlisting> +<screen> + company | tdate | price | first_value | max | count +----------+------------+-------+-------------+-----+------- + company1 | 2023-07-01 | 100 | 100 | 200 | 4 + company1 | 2023-07-02 | 200 | | | + company1 | 2023-07-03 | 150 | | | + company1 | 2023-07-04 | 140 | | | + company1 | 2023-07-05 | 150 | | | 0 + company1 | 2023-07-06 | 90 | 90 | 130 | 4 + company1 | 2023-07-07 | 110 | | | + company1 | 2023-07-08 | 130 | | | + company1 | 2023-07-09 | 120 | | | + company1 | 2023-07-10 | 130 | | | 0 +</screen> + </para> + <para> When a query involves multiple window functions, it is possible to write out each one with a separate <literal>OVER</literal> clause, but this is diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index d963f0a0a0..c3a8167c8e 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -21933,6 +21933,7 @@ SELECT count(*) FROM sometable; returns <literal>NULL</literal> if there is no such row. </para></entry> </row> + </tbody> </tgroup> </table> @@ -21972,6 +21973,59 @@ SELECT count(*) FROM sometable; Other frame specifications can be used to obtain other effects. </para> + <para> + Row pattern recognition navigation functions are listed in + <xref linkend="functions-rpr-navigation-table"/>. These functions + can be used to describe DEFINE clause of Row pattern recognition. + </para> + + <table id="functions-rpr-navigation-table"> + <title>Row Pattern Navigation Functions</title> + <tgroup cols="1"> + <thead> + <row> + <entry role="func_table_entry"><para role="func_signature"> + Function + </para> + <para> + Description + </para></entry> + </row> + </thead> + + <tbody> + <row> + <entry role="func_table_entry"><para role="func_signature"> + <indexterm> + <primary>prev</primary> + </indexterm> + <function>prev</function> ( <parameter>value</parameter> <type>anyelement</type> ) + <returnvalue>anyelement</returnvalue> + </para> + <para> + Returns the column value at the previous row; + returns NULL if there is no previous row in the window frame. + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <indexterm> + <primary>next</primary> + </indexterm> + <function>next</function> ( <parameter>value</parameter> <type>anyelement</type> ) + <returnvalue>anyelement</returnvalue> + </para> + <para> + Returns the column value at the next row; + returns NULL if there is no next row in the window frame. + </para></entry> + </row> + + </tbody> + </tgroup> + </table> + <note> <para> The SQL standard defines a <literal>RESPECT NULLS</literal> or diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml index 42d78913cf..522ad9dd70 100644 --- a/doc/src/sgml/ref/select.sgml +++ b/doc/src/sgml/ref/select.sgml @@ -969,8 +969,8 @@ WINDOW <replaceable class="parameter">window_name</replaceable> AS ( <replaceabl The <replaceable class="parameter">frame_clause</replaceable> can be one of <synopsis> -{ RANGE | ROWS | GROUPS } <replaceable>frame_start</replaceable> [ <replaceable>frame_exclusion</replaceable> ] -{ RANGE | ROWS | GROUPS } BETWEEN <replaceable>frame_start</replaceable> AND <replaceable>frame_end</replaceable> [ <replaceable>frame_exclusion</replaceable> ] +{ RANGE | ROWS | GROUPS } <replaceable>frame_start</replaceable> [ <replaceable>frame_exclusion</replaceable> ] [row_pattern_common_syntax] +{ RANGE | ROWS | GROUPS } BETWEEN <replaceable>frame_start</replaceable> AND <replaceable>frame_end</replaceable> [ <replaceable>frame_exclusion</replaceable> ] [row_pattern_common_syntax] </synopsis> where <replaceable>frame_start</replaceable> @@ -1077,6 +1077,40 @@ EXCLUDE NO OTHERS a given peer group will be in the frame or excluded from it. </para> + <para> + The + optional <replaceable class="parameter">row_pattern_common_syntax</replaceable> + defines the <firstterm>row pattern recognition condition</firstterm> for + this + window. <replaceable class="parameter">row_pattern_common_syntax</replaceable> + includes following subclauses. <literal>AFTER MATCH SKIP PAST LAST + ROW</literal> or <literal>AFTER MATCH SKIP TO NEXT ROW</literal> controls + how to proceed to next row position after a match + found. With <literal>AFTER MATCH SKIP PAST LAST ROW</literal> (the + default) next row position is next to the last row of previous match. On + the other hand, with <literal>AFTER MATCH SKIP TO NEXT ROW</literal> next + row position is always next to the last row of previous + match. <literal>DEFINE</literal> defines definition variables along with a + boolean expression. <literal>PATTERN</literal> defines a sequence of rows + that satisfies certain conditions using variables defined + in <literal>DEFINE</literal> clause. If the variable is not defined in + the <literal>DEFINE</literal> clause, it is implicitly assumed + following is defined in the <literal>DEFINE</literal> clause. + +<synopsis> +<literal>variable_name</literal> AS TRUE +</synopsis> + + Note that the maximu number of variables defined + in <literal>DEFINE</literal> clause is 26. + +<synopsis> +[ AFTER MATCH SKIP PAST LAST ROW | AFTER MATCH SKIP TO NEXT ROW ] +PATTERN <replaceable class="parameter">pattern_variable_name</replaceable>[+] [, ...] +DEFINE <replaceable class="parameter">definition_varible_name</replaceable> AS <replaceable class="parameter">expression</replaceable> [, ...] +</synopsis> + </para> + <para> The purpose of a <literal>WINDOW</literal> clause is to specify the behavior of <firstterm>window functions</firstterm> appearing in the query's -- 2.25.1 ----Next_Part(Wed_Nov__8_16_37_05_2023_872)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v11-0006-Row-pattern-recognition-patch-tests.patch" ^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: Virtual generated columns @ 2024-12-04 04:55 jian he <[email protected]> 2025-01-08 16:17 ` Re: Virtual generated columns Peter Eisentraut <[email protected]> 0 siblings, 1 reply; 3+ messages in thread From: jian he @ 2024-12-04 04:55 UTC (permalink / raw) To: Peter Eisentraut <[email protected]>; +Cc: pgsql-hackers; Dean Rasheed <[email protected]> On Fri, Nov 29, 2024 at 6:13 PM Peter Eisentraut <[email protected]> wrote: > > - Added support for virtual columns in trigger column lists. (For that, > I renamed ExecInitStoredGenerated() to ExecInitGenerated(), which > handles the computation of ri_extraUpdatedCols.) > why not duplicate some code from ExecInitStoredGenerated to ExecGetExtraUpdatedCols? * now the expression is that something initiated for the virtual generated column. which may not be necessary for virtual columns. let's make ResultRelInfo->ri_GeneratedExprsI, ResultRelInfo->ri_GeneratedExprsU be NULL for virtual columns. currently it may look like this: (gdb) p resultRelInfo->ri_GeneratedExprsU $20 = (ExprState **) 0x34f9638 (gdb) p resultRelInfo->ri_GeneratedExprsU[0] $21 = (ExprState *) 0x0 (gdb) p resultRelInfo->ri_GeneratedExprsU[1] $22 = (ExprState *) 0x0 (gdb) p resultRelInfo->ri_GeneratedExprsU[2] $23 = (ExprState *) 0x40 * ExecInitStoredGenerated main used in ExecComputeStoredGenerated. * we also need to slightly change ExecInitGenerated's comments. * in InitResultRelInfo, do we need explicit set ri_Generated_valid to false? * duplicate code won't have big performance issues, since build_column_default will take most of the time. the attached patch makes ExecInitStoredGenerated as is; duplicate some code from ExecInitStoredGenerated to ExecGetExtraUpdatedCols. Attachments: [application/octet-stream] v10-0001-refactor-ExecGetExtraUpdatedCols.no-cfbot (6.9K, ../../CACJufxHG+T4de6sSyxuM+SL7M1xM5sX+eTv1+C4SQGzigY=9uA@mail.gmail.com/2-v10-0001-refactor-ExecGetExtraUpdatedCols.no-cfbot) download ^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: Virtual generated columns 2024-12-04 04:55 Re: Virtual generated columns jian he <[email protected]> @ 2025-01-08 16:17 ` Peter Eisentraut <[email protected]> 0 siblings, 0 replies; 3+ messages in thread From: Peter Eisentraut @ 2025-01-08 16:17 UTC (permalink / raw) To: jian he <[email protected]>; +Cc: pgsql-hackers; Dean Rasheed <[email protected]> On 04.12.24 05:55, jian he wrote: > On Fri, Nov 29, 2024 at 6:13 PM Peter Eisentraut <[email protected]> wrote: >> >> - Added support for virtual columns in trigger column lists. (For that, >> I renamed ExecInitStoredGenerated() to ExecInitGenerated(), which >> handles the computation of ri_extraUpdatedCols.) >> > > why not duplicate some code from ExecInitStoredGenerated to > ExecGetExtraUpdatedCols? This answers itself: I'd rather not duplicate code. I don't see that as an improvement. > * now the expression is that something initiated for the virtual > generated column. which may not be necessary for virtual columns. > let's make ResultRelInfo->ri_GeneratedExprsI, > ResultRelInfo->ri_GeneratedExprsU be NULL for virtual columns. > > currently it may look like this: > (gdb) p resultRelInfo->ri_GeneratedExprsU > $20 = (ExprState **) 0x34f9638 > (gdb) p resultRelInfo->ri_GeneratedExprsU[0] > $21 = (ExprState *) 0x0 > (gdb) p resultRelInfo->ri_GeneratedExprsU[1] > $22 = (ExprState *) 0x0 > (gdb) p resultRelInfo->ri_GeneratedExprsU[2] > $23 = (ExprState *) 0x40 I have fixed that in v11. > * ExecInitStoredGenerated main used in ExecComputeStoredGenerated. > * we also need to slightly change ExecInitGenerated's comments. also fixed > * in InitResultRelInfo, do we need explicit set ri_Generated_valid to false? Doesn't seem necessary. The struct is initialized to zero at the beginning. ^ permalink raw reply [nested|flat] 3+ messages in thread
end of thread, other threads:[~2025-01-08 16:17 UTC | newest] Thread overview: 3+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2023-11-08 06:57 [PATCH v11 5/7] Row pattern recognition patch (docs). Tatsuo Ishii <[email protected]> 2024-12-04 04:55 Re: Virtual generated columns jian he <[email protected]> 2025-01-08 16:17 ` Re: Virtual generated columns Peter Eisentraut <[email protected]>
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