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* Refactor addition of PlaceHolderVars to joinrel targetlists.Tom Lane2022-08-17
| | | | | | | | | | | | | | | | | | | Make build_joinrel_tlist() responsible for adding PHVs that were already computed in one or the other input relation, and therefore change add_placeholders_to_joinrel() to only add PHVs that will be newly computed in this joinrel's output. This makes the handling of PHVs in build_joinrel_tlist() more like its handling of plain Vars, which seems like a good thing on intelligibility grounds and will simplify planned future changes. There is a purely cosmetic side-effect that the order of entries in the joinrel's tlist may change; but since it becomes more like the order of entries in the input tlists, that's not bad. The reason it wasn't done like this originally was the potential cost of looking up PlaceHolderInfo entries to consult ph_needed. Now that that's O(1) it shouldn't hurt. Discussion: https://postgr.es/m/1405792.1660677844@sss.pgh.pa.us
* Use an explicit state flag to control PlaceHolderInfo creation.Tom Lane2022-08-17
| | | | | | | | | | | | | | | | | | | Up to now, callers of find_placeholder_info() were required to pass a flag indicating if it's OK to make a new PlaceHolderInfo. That'd be fine if the callers had free choice, but they do not. Once we begin deconstruct_jointree() it's no longer OK to make more PHIs; while callers before that always want to create a PHI if it's not there already. So there's no freedom of action, only the opportunity to cause bugs by creating PHIs too late. Let's get rid of that in favor of adding a state flag PlannerInfo.placeholdersFrozen, which we can set at the point where it's no longer OK to make more PHIs. This patch also simplifies a couple of call sites that were using complicated logic to avoid calling find_placeholder_info() as much as possible. Now that that lookup is O(1) thanks to the previous commit, the extra bitmap manipulations are probably a net negative. Discussion: https://postgr.es/m/1405792.1660677844@sss.pgh.pa.us
* Make PlaceHolderInfo lookup O(1).Tom Lane2022-08-17
| | | | | | | | | | | | | Up to now we've just searched the placeholder_list when we want to find the PlaceHolderInfo with a given ID. While there's no evidence of that being a problem in the field, an upcoming patch will add find_placeholder_info() calls in build_joinrel_tlist(), which seems likely to make it more of an issue: a joinrel emitting lots of PlaceHolderVars would incur O(N^2) cost, and we might be building a lot of joinrels in complex queries. Hence, add an array that can be indexed directly by phid to make the lookups constant-time. Discussion: https://postgr.es/m/1405792.1660677844@sss.pgh.pa.us
* Avoid using list_length() to test for empty list.Tom Lane2022-08-17
| | | | | | | | | | | | | | | | | | | | | | | | The standard way to check for list emptiness is to compare the List pointer to NIL; our list code goes out of its way to ensure that that is the only representation of an empty list. (An acceptable alternative is a plain boolean test for non-null pointer, but explicit mention of NIL is usually preferable.) Various places didn't get that memo and expressed the condition with list_length(), which might not be so bad except that there were such a variety of ways to check it exactly: equal to zero, less than or equal to zero, less than one, yadda yadda. In the name of code readability, let's standardize all those spellings as "list == NIL" or "list != NIL". (There's probably some microscopic efficiency gain too, though few of these look to be at all performance-critical.) A very small number of cases were left as-is because they seemed more consistent with other adjacent list_length tests that way. Peter Smith, with bikeshedding from a number of us Discussion: https://postgr.es/m/CAHut+PtQYe+ENX5KrONMfugf0q6NHg4hR5dAhqEXEc2eefFeig@mail.gmail.com
* Fix failure to set correct operator in window run conditionDavid Rowley2022-08-05
| | | | | | | | | | | | This was a simple omission in 9d9c02ccd where the code didn't correctly set the operator to use in the run condition OpExpr when the window function was both monotonically increasing and decreasing. Bug discovered by Julien Roze, although he did not report it. Reported-by: Phil Florent Discussion: https://postgr.es/m/PA4P191MB160009A09B9D0624359278CFBA9F9@PA4P191MB1600.EURP191.PROD.OUTLOOK.COM Backpatch-through: 15, where 9d9c02ccd was added
* Fix incorrect tests for SRFs in relation_can_be_sorted_early().Tom Lane2022-08-03
| | | | | | | | | | | | | | | | | | | | | | | | | Commit fac1b470a thought we could check for set-returning functions by testing only the top-level node in an expression tree. This is wrong in itself, and to make matters worse it encouraged others to make the same mistake, by exporting tlist.c's special-purpose IS_SRF_CALL() as a widely-visible macro. I can't find any evidence that anyone's taken the bait, but it was only a matter of time. Use expression_returns_set() instead, and stuff the IS_SRF_CALL() genie back in its bottle, this time with a warning label. I also added a couple of cross-reference comments. After a fair amount of fooling around, I've despaired of making a robust test case that exposes the bug reliably, so no test case here. (Note that the test case added by fac1b470a is itself broken, in that it doesn't notice if you remove the code change. The repro given by the bug submitter currently doesn't fail either in v15 or HEAD, though I suspect that may indicate an unrelated bug.) Per bug #17564 from Martijn van Oosterhout. Back-patch to v13, as the faulty patch was. Discussion: https://postgr.es/m/17564-c7472c2f90ef2da3@postgresql.org
* Improve performance of ORDER BY / DISTINCT aggregatesDavid Rowley2022-08-02
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | ORDER BY / DISTINCT aggreagtes have, since implemented in Postgres, been executed by always performing a sort in nodeAgg.c to sort the tuples in the current group into the correct order before calling the transition function on the sorted tuples. This was not great as often there might be an index that could have provided pre-sorted input and allowed the transition functions to be called as the rows come in, rather than having to store them in a tuplestore in order to sort them once all the tuples for the group have arrived. Here we change the planner so it requests a path with a sort order which supports the most amount of ORDER BY / DISTINCT aggregate functions and add new code to the executor to allow it to support the processing of ORDER BY / DISTINCT aggregates where the tuples are already sorted in the correct order. Since there can be many ORDER BY / DISTINCT aggregates in any given query level, it's very possible that we can't find an order that suits all of these aggregates. The sort order that the planner chooses is simply the one that suits the most aggregate functions. We take the most strictly sorted variation of each order and see how many aggregate functions can use that, then we try again with the order of the remaining aggregates to see if another order would suit more aggregate functions. For example: SELECT agg(a ORDER BY a),agg2(a ORDER BY a,b) ... would request the sort order to be {a, b} because {a} is a subset of the sort order of {a,b}, but; SELECT agg(a ORDER BY a),agg2(a ORDER BY c) ... would just pick a plan ordered by {a} (we give precedence to aggregates which are earlier in the targetlist). SELECT agg(a ORDER BY a),agg2(a ORDER BY b),agg3(a ORDER BY b) ... would choose to order by {b} since two aggregates suit that vs just one that requires input ordered by {a}. Author: David Rowley Reviewed-by: Ronan Dunklau, James Coleman, Ranier Vilela, Richard Guo, Tom Lane Discussion: https://postgr.es/m/CAApHDvpHzfo92%3DR4W0%2BxVua3BUYCKMckWAmo-2t_KiXN-wYH%3Dw%40mail.gmail.com
* Relax overly strict rules in select_outer_pathkeys_for_merge()David Rowley2022-08-02
| | | | | | | | | | | | | | | | | | The select_outer_pathkeys_for_merge function made an attempt to build the merge join pathkeys in the same order as query_pathkeys. This was done as it may have led to no sort being required for an ORDER BY or GROUP BY clause in the upper planner. However, this restriction seems overly strict as it required that we match the query_pathkeys entirely or we don't bother putting the merge join pathkeys in that order. Here we relax this rule so that we use a prefix of the query_pathkeys providing that prefix matches all of the join quals. This may provide the upper planner with partially sorted input which will allow the use of incremental sorts instead of full sorts. Author: David Rowley Reviewed-by: Richard Guo Discussion: https://postgr.es/m/CAApHDvrtZu0PHVfDPFM4Yx3jNR2Wuwosv+T2zqa7LrhhBr2rRg@mail.gmail.com
* Fix incorrect is-this-the-topmost-join tests in parallel planning.Tom Lane2022-07-30
| | | | | | | | | | | | | | | | | | | | Two callers of generate_useful_gather_paths were testing the wrong thing when deciding whether to call that function: they checked for being at the top of the current join subproblem, rather than being at the actual top join. This'd result in failing to construct parallel paths for a sub-join for which they might be useful. While set_rel_pathlist() isn't actively broken, it seems best to make its identical-in-intention test for this be like the other two. This has been wrong all along, but given the lack of field complaints I'm hesitant to back-patch into stable branches; we usually prefer to avoid non-bug-fix changes in plan choices in minor releases. It seems not too late for v15 though. Richard Guo, reviewed by Antonin Houska and Tom Lane Discussion: https://postgr.es/m/CAMbWs4-mH8Zf87-w+3P2J=nJB+5OyicO28ia9q_9o=Lamf_VHg@mail.gmail.com
* Remove fls(), use pg_leftmost_one_pos32() instead.Thomas Munro2022-07-22
| | | | | | | | | | | | | | Commit 4f658dc8 provided the traditional BSD fls() function in src/port/fls.c so it could be used in several places. Later we added a bunch of similar facilities in pg_bitutils.h, based on compiler builtins that map to hardware instructions. It's a bit confusing to have both 1-based and 0-based variants of this operation in use in different parts of the tree, and neither is blessed by a standard. Let's drop fls.c and the configure probe, and reuse the newer code. Reviewed-by: David Rowley <dgrowleyml@gmail.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/CA%2BhUKG%2B7dSX1XF8yFGmYk-%3D48dbjH2kmzZj16XvhbrWP-9BzRg%40mail.gmail.com
* Convert planner's AggInfo and AggTransInfo structs to proper Nodes.Tom Lane2022-07-19
| | | | | | | | | | | | This is mostly just to get outfuncs.c support for them, so that the agginfos and aggtransinfos lists can be dumped when dumping the contents of PlannerInfo. While here, improve some related comments; notably, clean up obsolete comments left over from when preprocess_minmax_aggregates had to make its own scan of the query tree. Discussion: https://postgr.es/m/742479.1658160504@sss.pgh.pa.us
* Estimate cost of elided SubqueryScan, Append, MergeAppend nodes better.Tom Lane2022-07-19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | setrefs.c contains logic to discard no-op SubqueryScan nodes, that is, ones that have no qual to check and copy the input targetlist unchanged. (Formally it's not very nice to be applying such optimizations so late in the planner, but there are practical reasons for it; mostly that we can't unify relids between the subquery and the parent query until we flatten the rangetable during setrefs.c.) This behavior falsifies our previous cost estimates, since we would've charged cpu_tuple_cost per row just to pass data through the node. Most of the time that's little enough to not matter, but there are cases where this effect visibly changes the plan compared to what you would've gotten with no sub-select. To improve the situation, make the callers of cost_subqueryscan tell it whether they think the targetlist is trivial. cost_subqueryscan already has the qual list, so it can check the other half of the condition easily. It could make its own determination of tlist triviality too, but doing so would be repetitive (for callers that may call it several times) or unnecessarily expensive (for callers that can determine this more cheaply than a general test would do). This isn't a 100% solution, because createplan.c also does things that can falsify any earlier estimate of whether the tlist is trivial. However, it fixes nearly all cases in practice, if results for the regression tests are anything to go by. setrefs.c also contains logic to discard no-op Append and MergeAppend nodes. We did have knowledge of that behavior at costing time, but somebody failed to update it when a check on parallel-awareness was added to the setrefs.c logic. Fix that while we're here. These changes result in two minor changes in query plans shown in our regression tests. Neither is relevant to the purposes of its test case AFAICT. Patch by me; thanks to Richard Guo for review. Discussion: https://postgr.es/m/2581077.1651703520@sss.pgh.pa.us
* Wrap overly long linesAlvaro Herrera2022-07-19
| | | | | | | | Reported by Richard Guo. Reviewed-by: Richard Guo <guofenglinux@gmail.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/CAMbWs4-3ywL_tPHJKk-Vvzr-tBaR--b6XxGGm8Xe7vsG38AWog@mail.gmail.com
* Attempt to fix compiler warning on old compilerPeter Eisentraut2022-07-16
| | | | | | Build farm member lapwing (using gcc 4.7.2) didn't like one part of 9fd45870c1436b477264c0c82eb195df52bc0919, raising a compiler warning. Revert that for now.
* Replace many MemSet calls with struct initializationPeter Eisentraut2022-07-16
| | | | | | | | | | | | | | This replaces all MemSet() calls with struct initialization where that is easily and obviously possible. (For example, some cases have to worry about padding bits, so I left those.) (The same could be done with appropriate memset() calls, but this patch is part of an effort to phase out MemSet(), so it doesn't touch memset() calls.) Reviewed-by: Ranier Vilela <ranier.vf@gmail.com> Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org> Discussion: https://www.postgresql.org/message-id/9847b13c-b785-f4e2-75c3-12ec77a3b05c@enterprisedb.com
* Remove support for Visual Studio 2013Michael Paquier2022-07-14
| | | | | | | | | | | | | | | | | | | | No members of the buildfarm are using this version of Visual Studio, resulting in all the code cleaned up here as being mostly dead, and VS2017 is the oldest version still supported. More versions could be cut, but the gain would be minimal, while removing only VS2013 has the advantage to remove from the core code all the dependencies on the value defined by _MSC_VER, where compatibility tweaks have accumulated across the years mostly around locales and strtof(), so that's a nice isolated cleanup. Note that this commit additionally allows a revert of 3154e16. The versions of Visual Studio now supported range from 2015 to 2022. Author: Michael Paquier Reviewed-by: Juan José Santamaría Flecha, Tom Lane, Thomas Munro, Justin Pryzby Discussion: https://postgr.es/m/YoH2IMtxcS3ncWn+@paquier.xyz
* Use list_copy_head() instead of list_truncate(list_copy(...), ...)David Rowley2022-07-13
| | | | | | | | | | | | | | | | Truncating off the end of a freshly copied List is not a very efficient way of copying the first N elements of a List. In many of the cases that are updated here, the pattern was only being used to remove the final element of a List. That's about the best case for it, but there were many instances where the truncate trimming the List down much further. 4cc832f94 added list_copy_head(), so let's use it in cases where it's useful. Author: David Rowley Discussion: https://postgr.es/m/1986787.1657666922%40sss.pgh.pa.us
* Tidy up code in get_cheapest_group_keys_order()David Rowley2022-07-13
| | | | | | | | | | | | | | | | | | | | | | | There are a few things that we could do a little better within get_cheapest_group_keys_order(): 1. We should be using list_free() rather than pfree() on a List. 2. We should use for_each_from() instead of manually coding a for loop to skip the first n elements of a List 3. list_truncate(list_copy(...), n) is not a great way to copy the first n elements of a list. Let's invent list_copy_head() for that. That way we don't need to copy the entire list just to truncate it directly afterwards. 4. We can simplify finding the cheapest cost by setting the cheapest cost variable to DBL_MAX. That allows us to skip special-casing the initial iteration of the loop. Author: David Rowley Discussion: https://postgr.es/m/CAApHDvrGyL3ft8waEkncG9y5HDMu5TFFJB1paoTC8zi9YK97Nw@mail.gmail.com Backpatch-through: 15, where get_cheapest_group_keys_order was added.
* Remove no-longer-used parameter for create_groupingsets_path().Tom Lane2022-07-01
| | | | | | | | numGroups is unused since commit b5635948a; let's get rid of it. XueJing Zhao, reviewed by Richard Guo Discussion: https://postgr.es/m/DM6PR05MB64923CC8B63A2CAF3B2E5D47B7AD9@DM6PR05MB6492.namprd05.prod.outlook.com
* Improve comments for trivial_subqueryscan().Etsuro Fujita2022-06-09
| | | | | | | | | | | | | | | | This function can be called from mark_async_capable_plan(), a helper function for create_append_plan(), before set_subqueryscan_references(), to determine the triviality of a SubqueryScan that is a child of an Append plan node, which is done before doing finalize_plan() on the SubqueryScan (if necessary) and set_plan_references() on the subplan, unlike when called from set_subqueryscan_references(). The reason why this is safe wouldn't be that obvious, so add comments explaining this. Follow-up for commit c2bb02bc2. Reviewed by Zhihong Yu. Discussion: https://postgr.es/m/CAPmGK17%2BGiJBthC6va7%2B9n6t75e-M1N0U18YB2G1B%2BE5OdrNTA%40mail.gmail.com
* Teach remove_unused_subquery_outputs about window run conditionsDavid Rowley2022-05-27
| | | | | | | | | | | | | | | | | | | | | | | | | 9d9c02ccd added code to allow the executor to take shortcuts when quals on monotonic window functions guaranteed that once the qual became false it could never become true again. When possible, baserestrictinfo quals are converted to become these quals, which we call run conditions. Unfortunately, in 9d9c02ccd, I forgot to update remove_unused_subquery_outputs to teach it about these run conditions. This could cause a WindowFunc column which was unused in the target list but referenced by an upper-level WHERE clause to be removed from the subquery when the qual in the WHERE clause was converted into a window run condition. Because of this, the entire WindowClause would be removed from the query resulting in additional rows making it into the resultset when they should have been filtered out by the WHERE clause. Here we fix this by recording which target list items in the subquery have run conditions. That gets passed along to remove_unused_subquery_outputs to tell it not to remove these items from the target list. Bug: #17495 Reported-by: Jeremy Evans Reviewed-by: Richard Guo Discussion: https://postgr.es/m/17495-7ffe2fa0b261b9fa@postgresql.org
* Avoid overflow hazard when clamping group counts to "long int".Tom Lane2022-05-21
| | | | | | | | | | | | | | | | | | | | | | | | Several places in the planner tried to clamp a double value to fit in a "long" by doing (long) Min(x, (double) LONG_MAX); This is subtly incorrect, because it casts LONG_MAX to double and potentially back again. If long is 64 bits then the double value is inexact, and the platform might round it up to LONG_MAX+1 resulting in an overflow and an undesirably negative output. While it's not hard to rewrite the expression into a safe form, let's put it into a common function to reduce the risk of someone doing it wrong in future. In principle this is a bug fix, but since the problem could only manifest with group count estimates exceeding 2^63, it seems unlikely that anyone has actually hit this or will do so anytime soon. We're fixing it mainly to satisfy fuzzer-type tools. That being the case, a HEAD-only fix seems sufficient. Andrey Lepikhov Discussion: https://postgr.es/m/ebbc2efb-7ef9-bf2f-1ada-d6ec48f70e58@postgrespro.ru
* Fix incorrect row estimates used for Memoize costingDavid Rowley2022-05-16
| | | | | | | | | | | | | | | | | | | | | | | | | | In order to estimate the cache hit ratio of a Memoize node, one of the inputs we require is the estimated number of times the Memoize node will be rescanned. The higher this number, the large the cache hit ratio is likely to become. Unfortunately, the value being passed as the number of "calls" to the Memoize was incorrectly using the Nested Loop's outer_path->parent->rows instead of outer_path->rows. This failed to account for the fact that the outer_path might be parameterized by some upper-level Nested Loop. This problem could lead to Memoize plans appearing more favorable than they might actually be. It could also lead to extended executor startup times when work_mem values were large due to the planner setting overly large MemoizePath->est_entries resulting in the Memoize hash table being initially made much larger than might be required. Fix this simply by passing outer_path->rows rather than outer_path->parent->rows. Also, adjust the expected regression test output for a plan change. Reported-by: Pavel Stehule Author: David Rowley Discussion: https://postgr.es/m/CAFj8pRAMp%3DQsMi6sPQJ4W3hczoFJRvyXHJV3AZAZaMyTVM312Q%40mail.gmail.com Backpatch-through: 14, where Memoize was introduced
* Pre-beta mechanical code beautification.Tom Lane2022-05-12
| | | | | Run pgindent, pgperltidy, and reformat-dat-files. I manually fixed a couple of comments that pgindent uglified.
* Make pull_var_clause() handle GroupingFuncs exactly like Aggrefs.Tom Lane2022-05-12
| | | | | | | | | | | | | | | | | This follows in the footsteps of commit 2591ee8ec by removing one more ill-advised shortcut from planning of GroupingFuncs. It's true that we don't intend to execute the argument expression(s) at runtime, but we still have to process any Vars appearing within them, or we risk failure at setrefs.c time (or more fundamentally, in EXPLAIN trying to print such an expression). Vars in upper plan nodes have to have referents in the next plan level, whether we ever execute 'em or not. Per bug #17479 from Michael J. Sullivan. Back-patch to all supported branches. Richard Guo Discussion: https://postgr.es/m/17479-6260deceaf0ad304@postgresql.org
* Fix rowcount estimate for SubqueryScan that's under a Gather.Tom Lane2022-05-04
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | SubqueryScan was always getting labeled with a rowcount estimate appropriate for non-parallel cases. However, nodes that are underneath a Gather should be treated as processing only one worker's share of the rows, whether the particular node is explicitly parallel-aware or not. Most non-scan-level node types get this right automatically because they base their rowcount estimate on that of their input sub-Path(s). But SubqueryScan didn't do that, instead using the whole-relation rowcount estimate as if it were a non-parallel-aware scan node. If there is a parallel-aware node below the SubqueryScan, this is wrong, and it results in inflating the cost estimates for nodes above the SubqueryScan, which can cause us to not choose a parallel plan, or choose a silly one --- as indeed is visible in the one regression test whose results change with this patch. (Although that plan tree appears to contain no SubqueryScans, there were some in it before setrefs.c deleted them.) To fix, use path->subpath->rows not baserel->tuples as the number of input tuples we'll process. This requires estimating the quals' selectivity afresh, which is slightly annoying; but it shouldn't really add much cost thanks to the caching done in RestrictInfo. This is pretty clearly a bug fix, but I'll refrain from back-patching as people might not appreciate plan choices changing in stable branches. The fact that it took us this long to identify the bug suggests that it's not a major problem. Per report from bucoo, though this is not his proposed patch. Discussion: https://postgr.es/m/202204121457159307248@sohu.com
* Disable asynchronous execution if using gating Result nodes.Etsuro Fujita2022-04-28
| | | | | | | | | | | | | | | | | | | | | | | | | | | | mark_async_capable_plan(), which is called from create_append_plan() to determine whether subplans are async-capable, failed to take into account that the given subplan created from a given subpath might include a gating Result node if the subpath is a SubqueryScanPath or ForeignPath, causing a segmentation fault there when the subplan created from a SubqueryScanPath includes the Result node, or causing ExecAsyncRequest() to throw an error about an unrecognized node type when the subplan created from a ForeignPath includes the Result node, because in the latter case the Result node was unintentionally considered as async-capable, but we don't currently support executing Result nodes asynchronously. Fix by modifying mark_async_capable_plan() to disable asynchronous execution in such cases. Also, adjust code in the ProjectionPath case in mark_async_capable_plan(), for consistency with other cases, and adjust/improve comments there. is_async_capable_path() added in commit 27e1f1456, which was rewritten to mark_async_capable_plan() in a later commit, has the same issue, causing the error at execution mentioned above, so back-patch to v14 where the aforesaid commit went in. Per report from Justin Pryzby. Etsuro Fujita, reviewed by Zhihong Yu and Justin Pryzby. Discussion: https://postgr.es/m/20220408124338.GK24419%40telsasoft.com
* Remove inadequate assertion check in CTE inlining.Tom Lane2022-04-21
| | | | | | | | | | | | | | | | | | | | inline_cte() expected to find exactly as many references to the target CTE as its cterefcount indicates. While that should be accurate for the tree as emitted by the parser, there are some optimizations that occur upstream of here that could falsify it, notably removal of unused subquery output expressions. Trying to make the accounting 100% accurate seems expensive and doomed to future breakage. It's not really worth it, because all this code is protecting is downstream assumptions that every referenced CTE has a plan. Let's convert those assertions to regular test-and-elog just in case there's some actual problem, and then drop the failing assertion. Per report from Tomas Vondra (thanks also to Richard Guo for analysis). Back-patch to v12 where the faulty code came in. Discussion: https://postgr.es/m/29196a1e-ed47-c7ca-9be2-b1c636816183@enterprisedb.com
* Remove extraneous blank lines before block-closing bracesAlvaro Herrera2022-04-13
| | | | | | | | | These are useless and distracting. We wouldn't have written the code with them to begin with, so there's no reason to keep them. Author: Justin Pryzby <pryzby@telsasoft.com> Discussion: https://postgr.es/m/20220411020336.GB26620@telsasoft.com Discussion: https://postgr.es/m/attachment/133167/0016-Extraneous-blank-lines.patch
* Change mechanism to set up source targetlist in MERGEAlvaro Herrera2022-04-12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We were setting MERGE source subplan's targetlist by expanding the individual attributes of the source relation completely, early in the parse analysis phase. This failed to work when the condition of an action included a whole-row reference, causing setrefs.c to error out with ERROR: variable not found in subplan target lists because at that point there is nothing to resolve the whole-row reference with. We can fix this by having preprocess_targetlist expand the source targetlist for Vars required from the source rel by all actions. Moreover, by using this expansion mechanism we can do away with the targetlist expansion in transformMergeStmt, which is good because then we no longer pull in columns that aren't needed for anything. Add a test case for the problem. While at it, remove some redundant code in preprocess_targetlist(): MERGE was doing separately what is already being done for UPDATE/DELETE, so we can just rely on the latter and remove the former. (The handling of inherited rels was different for MERGE, but that was a no-longer- necessary hack.) Fix outdated, related comments for fix_join_expr also. Author: Richard Guo <guofenglinux@gmail.com> Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Reported-by: Joe Wildish <joe@lateraljoin.com> Discussion: https://postgr.es/m/fab3b90a-914d-46a9-beb0-df011ee39ee5@www.fastmail.com
* Fix various typos and spelling mistakes in code commentsDavid Rowley2022-04-11
| | | | | Author: Justin Pryzby Discussion: https://postgr.es/m/20220411020336.GB26620@telsasoft.com
* Teach planner and executor about monotonic window funcsDavid Rowley2022-04-08
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Window functions such as row_number() always return a value higher than the previously returned value for tuples in any given window partition. Traditionally queries such as; SELECT * FROM ( SELECT *, row_number() over (order by c) rn FROM t ) t WHERE rn <= 10; were executed fairly inefficiently. Neither the query planner nor the executor knew that once rn made it to 11 that nothing further would match the outer query's WHERE clause. It would blindly continue until all tuples were exhausted from the subquery. Here we implement means to make the above execute more efficiently. This is done by way of adding a pg_proc.prosupport function to various of the built-in window functions and adding supporting code to allow the support function to inform the planner if the window function is monotonically increasing, monotonically decreasing, both or neither. The planner is then able to make use of that information and possibly allow the executor to short-circuit execution by way of adding a "run condition" to the WindowAgg to allow it to determine if some of its execution work can be skipped. This "run condition" is not like a normal filter. These run conditions are only built using quals comparing values to monotonic window functions. For monotonic increasing functions, quals making use of the btree operators for <, <= and = can be used (assuming the window function column is on the left). You can see here that once such a condition becomes false that a monotonic increasing function could never make it subsequently true again. For monotonically decreasing functions the >, >= and = btree operators for the given type can be used for run conditions. The best-case situation for this is when there is a single WindowAgg node without a PARTITION BY clause. Here when the run condition becomes false the WindowAgg node can simply return NULL. No more tuples will ever match the run condition. It's a little more complex when there is a PARTITION BY clause. In this case, we cannot return NULL as we must still process other partitions. To speed this case up we pull tuples from the outer plan to check if they're from the same partition and simply discard them if they are. When we find a tuple belonging to another partition we start processing as normal again until the run condition becomes false or we run out of tuples to process. When there are multiple WindowAgg nodes to evaluate then this complicates the situation. For intermediate WindowAggs we must ensure we always return all tuples to the calling node. Any filtering done could lead to incorrect results in WindowAgg nodes above. For all intermediate nodes, we can still save some work when the run condition becomes false. We've no need to evaluate the WindowFuncs anymore. Other WindowAgg nodes cannot reference the value of these and these tuples will not appear in the final result anyway. The savings here are small in comparison to what can be saved in the top-level WingowAgg, but still worthwhile. Intermediate WindowAgg nodes never filter out tuples, but here we change WindowAgg so that the top-level WindowAgg filters out tuples that don't match the intermediate WindowAgg node's run condition. Such filters appear in the "Filter" clause in EXPLAIN for the top-level WindowAgg node. Here we add prosupport functions to allow the above to work for; row_number(), rank(), dense_rank(), count(*) and count(expr). It appears technically possible to do the same for min() and max(), however, it seems unlikely to be useful enough, so that's not done here. Bump catversion Author: David Rowley Reviewed-by: Andy Fan, Zhihong Yu Discussion: https://postgr.es/m/CAApHDvqvp3At8++yF8ij06sdcoo1S_b2YoaT9D4Nf+MObzsrLQ@mail.gmail.com
* Allow asynchronous execution in more cases.Etsuro Fujita2022-04-06
| | | | | | | | | | | | | | | | In commit 27e1f1456, create_append_plan() only allowed the subplan created from a given subpath to be executed asynchronously when it was an async-capable ForeignPath. To extend coverage, this patch handles cases when the given subpath includes some other Path types as well that can be omitted in the plan processing, such as a ProjectionPath directly atop an async-capable ForeignPath, allowing asynchronous execution in partitioned-scan/partitioned-join queries with non-Var tlist expressions and more UNION queries. Andrey Lepikhov and Etsuro Fujita, reviewed by Alexander Pyhalov and Zhihong Yu. Discussion: https://postgr.es/m/659c37a8-3e71-0ff2-394c-f04428c76f08%40postgrespro.ru
* Fix comments with "a expression"Andrew Dunstan2022-03-31
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* Fix postgres_fdw to check shippability of sort clauses properly.Tom Lane2022-03-31
| | | | | | | | | | | | | | | | | | | | | | | | | postgres_fdw would push ORDER BY clauses to the remote side without verifying that the sort operator is safe to ship. Moreover, it failed to print a suitable USING clause if the sort operator isn't default for the sort expression's type. The net result of this is that the remote sort might not have anywhere near the semantics we expect, which'd be disastrous for locally-performed merge joins in particular. We addressed similar issues in the context of ORDER BY within an aggregate function call in commit 7012b132d, but failed to notice that query-level ORDER BY was broken. Thus, much of the necessary logic already existed, but it requires refactoring to be usable in both cases. Back-patch to all supported branches. In HEAD only, remove the core code's copy of find_em_expr_for_rel, which is no longer used and really should never have been pushed into equivclass.c in the first place. Ronan Dunklau, per report from David Rowley; reviews by David Rowley, Ranier Vilela, and myself Discussion: https://postgr.es/m/CAApHDvr4OeC2DBVY--zVP83-K=bYrTD7F8SZDhN4g+pj2f2S-A@mail.gmail.com
* Optimize order of GROUP BY keysTomas Vondra2022-03-31
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When evaluating a query with a multi-column GROUP BY clause using sort, the cost may be heavily dependent on the order in which the keys are compared when building the groups. Grouping does not imply any ordering, so we're allowed to compare the keys in arbitrary order, and a Hash Agg leverages this. But for Group Agg, we simply compared keys in the order as specified in the query. This commit explores alternative ordering of the keys, trying to find a cheaper one. In principle, we might generate grouping paths for all permutations of the keys, and leave the rest to the optimizer. But that might get very expensive, so we try to pick only a couple interesting orderings based on both local and global information. When planning the grouping path, we explore statistics (number of distinct values, cost of the comparison function) for the keys and reorder them to minimize comparison costs. Intuitively, it may be better to perform more expensive comparisons (for complex data types etc.) last, because maybe the cheaper comparisons will be enough. Similarly, the higher the cardinality of a key, the lower the probability we’ll need to compare more keys. The patch generates and costs various orderings, picking the cheapest ones. The ordering of group keys may interact with other parts of the query, some of which may not be known while planning the grouping. E.g. there may be an explicit ORDER BY clause, or some other ordering-dependent operation, higher up in the query, and using the same ordering may allow using either incremental sort or even eliminate the sort entirely. The patch generates orderings and picks those minimizing the comparison cost (for various pathkeys), and then adds orderings that might be useful for operations higher up in the plan (ORDER BY, etc.). Finally, it always keeps the ordering specified in the query, on the assumption the user might have additional insights. This introduces a new GUC enable_group_by_reordering, so that the optimization may be disabled if needed. The original patch was proposed by Teodor Sigaev, and later improved and reworked by Dmitry Dolgov. Reviews by a number of people, including me, Andrey Lepikhov, Claudio Freire, Ibrar Ahmed and Zhihong Yu. Author: Dmitry Dolgov, Teodor Sigaev, Tomas Vondra Reviewed-by: Tomas Vondra, Andrey Lepikhov, Claudio Freire, Ibrar Ahmed, Zhihong Yu Discussion: https://postgr.es/m/7c79e6a5-8597-74e8-0671-1c39d124c9d6%40sigaev.ru Discussion: https://postgr.es/m/CA%2Bq6zcW_4o2NC0zutLkOJPsFt80megSpX_dVRo6GK9PC-Jx_Ag%40mail.gmail.com
* SQL/JSON query functionsAndrew Dunstan2022-03-29
| | | | | | | | | | | | | | | | | | | | | | | | | | | This introduces the SQL/JSON functions for querying JSON data using jsonpath expressions. The functions are: JSON_EXISTS() JSON_QUERY() JSON_VALUE() All of these functions only operate on jsonb. The workaround for now is to cast the argument to jsonb. JSON_EXISTS() tests if the jsonpath expression applied to the jsonb value yields any values. JSON_VALUE() must return a single value, and an error occurs if it tries to return multiple values. JSON_QUERY() must return a json object or array, and there are various WRAPPER options for handling scalar or multi-value results. Both these functions have options for handling EMPTY and ERROR conditions. Nikita Glukhov Reviewers have included (in no particular order) Andres Freund, Alexander Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zihong Yu, Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby. Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
* Add support for MERGE SQL commandAlvaro Herrera2022-03-28
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | MERGE performs actions that modify rows in the target table using a source table or query. MERGE provides a single SQL statement that can conditionally INSERT/UPDATE/DELETE rows -- a task that would otherwise require multiple PL statements. For example, MERGE INTO target AS t USING source AS s ON t.tid = s.sid WHEN MATCHED AND t.balance > s.delta THEN UPDATE SET balance = t.balance - s.delta WHEN MATCHED THEN DELETE WHEN NOT MATCHED AND s.delta > 0 THEN INSERT VALUES (s.sid, s.delta) WHEN NOT MATCHED THEN DO NOTHING; MERGE works with regular tables, partitioned tables and inheritance hierarchies, including column and row security enforcement, as well as support for row and statement triggers and transition tables therein. MERGE is optimized for OLTP and is parameterizable, though also useful for large scale ETL/ELT. MERGE is not intended to be used in preference to existing single SQL commands for INSERT, UPDATE or DELETE since there is some overhead. MERGE can be used from PL/pgSQL. MERGE does not support targetting updatable views or foreign tables, and RETURNING clauses are not allowed either. These limitations are likely fixable with sufficient effort. Rewrite rules are also not supported, but it's not clear that we'd want to support them. Author: Pavan Deolasee <pavan.deolasee@gmail.com> Author: Álvaro Herrera <alvherre@alvh.no-ip.org> Author: Amit Langote <amitlangote09@gmail.com> Author: Simon Riggs <simon.riggs@enterprisedb.com> Reviewed-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com> Reviewed-by: Andres Freund <andres@anarazel.de> (earlier versions) Reviewed-by: Peter Geoghegan <pg@bowt.ie> (earlier versions) Reviewed-by: Robert Haas <robertmhaas@gmail.com> (earlier versions) Reviewed-by: Japin Li <japinli@hotmail.com> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com> Reviewed-by: Zhihong Yu <zyu@yugabyte.com> Discussion: https://postgr.es/m/CANP8+jKitBSrB7oTgT9CY2i1ObfOt36z0XMraQc+Xrz8QB0nXA@mail.gmail.com Discussion: https://postgr.es/m/CAH2-WzkJdBuxj9PO=2QaO9-3h3xGbQPZ34kJH=HukRekwM-GZg@mail.gmail.com Discussion: https://postgr.es/m/20201231134736.GA25392@alvherre.pgsql
* SQL/JSON constructorsAndrew Dunstan2022-03-27
| | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch introduces the SQL/JSON standard constructors for JSON: JSON() JSON_ARRAY() JSON_ARRAYAGG() JSON_OBJECT() JSON_OBJECTAGG() For the most part these functions provide facilities that mimic existing json/jsonb functions. However, they also offer some useful additional functionality. In addition to text input, the JSON() function accepts bytea input, which it will decode and constuct a json value from. The other functions provide useful options for handling duplicate keys and null values. This series of patches will be followed by a consolidated documentation patch. Nikita Glukhov Reviewers have included (in no particular order) Andres Freund, Alexander Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zihong Yu, Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby. Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
* Common SQL/JSON clausesAndrew Dunstan2022-03-27
| | | | | | | | | | | | | | | | | This introduces some of the building blocks used by the SQL/JSON constructor and query functions. Specifically, it provides node executor and grammar support for the FORMAT JSON [ENCODING foo] clause, and values decorated with it, and for the RETURNING clause. The following SQL/JSON patches will leverage these. Nikita Glukhov (who probably deserves an award for perseverance). Reviewers have included (in no particular order) Andres Freund, Alexander Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zihong Yu, Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby. Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
* Remove useless variable.Tom Lane2022-03-27
| | | | | | | flatten_join_alias_vars_mutator counted attnums, but didn't do anything with the count (no doubt it did at one time). Noted by buildfarm member seawasp.
* Invent recursive_worktable_factor GUC to replace hard-wired constant.Tom Lane2022-03-24
| | | | | | | | | | | | Up to now, the planner estimated the size of a recursive query's worktable as 10 times the size of the non-recursive term. It's hard to see how to do significantly better than that automatically, but we can give users control over the multiplier to allow tuning for specific use-cases. The default behavior remains the same. Simon Riggs Discussion: https://postgr.es/m/CANbhV-EuaLm4H3g0+BSTYHEGxJj3Kht0R+rJ8vT57Dejnh=_nA@mail.gmail.com
* Revert "Common SQL/JSON clauses"Andrew Dunstan2022-03-22
| | | | | | This reverts commit 865fe4d5df560a6f5353da652018ff876978ad2d. This has caused issues with a significant number of buildfarm members
* Common SQL/JSON clausesAndrew Dunstan2022-03-22
| | | | | | | | | | | | | | | | | This introduces some of the building blocks used by the SQL/JSON constructor and query functions. Specifically, it provides node executor and grammar support for the FORMAT JSON [ENCODING foo] clause, and values decorated with it, and for the RETURNING clause. The following SQL/JSON patches will leverage these. Nikita Glukhov (who probably deserves an award for perseverance). Reviewers have included (in no particular order) Andres Freund, Alexander Korotkov, Pavel Stehule, Andrew Alsup. Erik Rijkers, Zihong Yu and Himanshu Upadhyaya. Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
* Fix assorted missing logic for GroupingFunc nodes.Tom Lane2022-03-21
| | | | | | | | | | | | | | | | | | | | | | The planner needs to treat GroupingFunc like Aggref for many purposes, in particular with respect to processing of the argument expressions, which are not to be evaluated at runtime. A few places hadn't gotten that memo, notably including subselect.c's processing of outer-level aggregates. This resulted in assertion failures or wrong plans for cases in which a GROUPING() construct references an outer aggregation level. Also fix missing special cases for GroupingFunc in cost_qual_eval (resulting in wrong cost estimates for GROUPING(), although it's not clear that that would affect plan shapes in practice) and in ruleutils.c (resulting in excess parentheses in pretty-print mode). Per bug #17088 from Yaoguang Chen. Back-patch to all supported branches. Richard Guo, Tom Lane Discussion: https://postgr.es/m/17088-e33882b387de7f5c@postgresql.org
* Don't bother to attach column name lists to RowExprs of named types.Tom Lane2022-03-17
| | | | | | | | | If a RowExpr is marked as returning a named composite type, we aren't going to consult its colnames list; we'll use the attribute names shown for the type in pg_attribute. Hence, skip storing that list, to save a few nanoseconds when copying the expression tree around. Discussion: https://postgr.es/m/2950001.1638729947@sss.pgh.pa.us
* Parse/analyze function renamingPeter Eisentraut2022-03-04
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There are three parallel ways to call parse/analyze: with fixed parameters, with variable parameters, and by supplying your own parser callback. Some of the involved functions were confusingly named and made this API structure more confusing. This patch renames some functions to make this clearer: parse_analyze() -> parse_analyze_fixedparams() pg_analyze_and_rewrite() -> pg_analyze_and_rewrite_fixedparams() (Otherwise one might think this variant doesn't accept parameters, but in fact all three ways accept parameters.) pg_analyze_and_rewrite_params() -> pg_analyze_and_rewrite_withcb() (Before, and also when considering pg_analyze_and_rewrite(), one might think this is the only way to pass parameters. Moreover, the parser callback doesn't necessarily need to parse only parameters, it's just one of the things it could do.) parse_fixed_parameters() -> setup_parse_fixed_parameters() parse_variable_parameters() -> setup_parse_variable_parameters() (These functions don't actually do any parsing, they just set up callbacks to use during parsing later.) This patch also adds some const decorations to the fixed-parameters API, so the distinction from the variable-parameters API is more clear. Reviewed-by: Nathan Bossart <bossartn@amazon.com> Discussion: https://www.postgresql.org/message-id/flat/c67ce276-52b4-0239-dc0e-39875bf81840@enterprisedb.com
* Don't use_physical_tlist for an IOS with non-returnable columns.Tom Lane2022-02-11
| | | | | | | | | | | | | | | | | createplan.c tries to save a runtime projection step by specifying a scan plan node's output as being exactly the table's columns, or index's columns in the case of an index-only scan, if there is not a reason to do otherwise. This logic did not previously pay attention to whether an index's columns are returnable. That worked, sort of accidentally, until commit 9a3ddeb51 taught setrefs.c to reject plans that try to read a non-returnable column. I have no desire to loosen setrefs.c's new check, so instead adjust use_physical_tlist() to not try to optimize this way when there are non-returnable column(s). Per report from Ryan Kelly. Like the previous patch, back-patch to all supported branches. Discussion: https://postgr.es/m/CAHUie24ddN+pDNw7fkhNrjrwAX=fXXfGZZEHhRuofV_N_ftaSg@mail.gmail.com
* Consider parallel awareness when removing single-child AppendsDavid Rowley2022-01-25
| | | | | | | | | | | | | | | | | 8edd0e794 added some code to remove Append and MergeAppend nodes when they contained a single child node. As it turned out, this was unsafe to do when the Append/MergeAppend was parallel_aware and the child node was not. Removing the Append/MergeAppend, in this case, could lead to the child plan being called multiple times by parallel workers when it was unsafe to do so. Here we fix this by just not removing the Append/MergeAppend when the parallel_aware flag of the parent and child node don't match. Reported-by: Yura Sokolov Bug: #17335 Discussion: https://postgr.es/m/b59605fecb20ba9ea94e70ab60098c237c870628.camel%40postgrespro.ru Backpatch-through: 12, where 8edd0e794 was first introduced
* Fix various typos, grammar and code style in comments and docsMichael Paquier2022-01-25
| | | | | | | | | This fixes a set of issues that have accumulated over the past months (or years) in various code areas. Most fixes are related to some recent additions, as of the development of v15. Author: Justin Pryzby Discussion: https://postgr.es/m/20220124030001.GQ23027@telsasoft.com
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