300 Commits (2226b4189bb4ccfcc53917a8695d24e91ff2f950)

Author	SHA1	Message	Date
Peter Eisentraut	2226b4189b	Change SeqScan node to contain Scan node ... This makes the structure of all Scan-derived nodes the same, independent of whether they have additional fields. Discussion: https://www.postgresql.org/message-id/flat/c1097590-a6a4-486a-64b1-e1f9cc0533ce@enterprisedb.com	4 years ago
Tom Lane	a49d081235	Replace explicit PIN entries in pg_depend with an OID range test. ... As of v14, pg_depend contains almost 7000 "pin" entries recording the OIDs of built-in objects. This is a fair amount of bloat for every database, and it adds time to pg_depend lookups as well as initdb. We can get rid of all of those entries in favor of an OID range check, i.e. "OIDs below FirstUnpinnedObjectId are pinned". (template1 and the public schema are exceptions. Those exceptions are now wired into IsPinnedObject() instead of initdb's code for filling pg_depend, but it's the same amount of cruft either way.) The contents of pg_shdepend are modified likewise. Discussion: https://postgr.es/m/3737988.1618451008@sss.pgh.pa.us	4 years ago
David Rowley	83f4fcc655	Change the name of the Result Cache node to Memoize ... "Result Cache" was never a great name for this node, but nobody managed to come up with another name that anyone liked enough. That was until David Johnston mentioned "Node Memoization", which Tom Lane revised to just "Memoize". People seem to like "Memoize", so let's do the rename. Reviewed-by: Justin Pryzby Discussion: https://postgr.es/m/20210708165145.GG1176@momjian.us Backpatch-through: 14, where Result Cache was introduced	4 years ago
David Rowley	29f45e299e	Use a hash table to speed up NOT IN(values) ... Similar to 50e17ad28, which allowed hash tables to be used for IN clauses with a set of constants, here we add the same feature for NOT IN clauses. NOT IN evaluates the same as: WHERE a <> v1 AND a <> v2 AND a <> v3. Obviously, if we're using a hash table we must be exactly equivalent to that and return the same result taking into account that either side of the condition could contain a NULL. This requires a little bit of special handling to make work with the hash table version. When processing NOT IN, the ScalarArrayOpExpr's operator will be the <> operator. To be able to build and lookup a hash table we must use the <>'s negator operator. The planner checks if that exists and is hashable and sets the relevant fields in ScalarArrayOpExpr to instruct the executor to use hashing. Author: David Rowley, James Coleman Reviewed-by: James Coleman, Zhihong Yu Discussion: https://postgr.es/m/CAApHDvoF1mum_FRk6D621edcB6KSHBi2+GAgWmioj5AhOu2vwQ@mail.gmail.com	4 years ago
David Rowley	cba5c70b95	Fix setrefs.c code for Result Cache nodes ... Result Cache, added in 9eacee2e6 neglected to properly adjust the plan references in setrefs.c. This could lead to the following error during EXPLAIN: ERROR: cannot decompile join alias var in plan tree Fix that. Bug: 17030 Reported-by: Hans Buschmann Discussion: https://postgr.es/m/17030-5844aecae42fe223@postgresql.org	4 years ago
David Rowley	50e17ad281	Speedup ScalarArrayOpExpr evaluation ... ScalarArrayOpExprs with "useOr=true" and a set of Consts on the righthand side have traditionally been evaluated by using a linear search over the array. When these arrays contain large numbers of elements then this linear search could become a significant part of execution time. Here we add a new method of evaluating ScalarArrayOpExpr expressions to allow them to be evaluated by first building a hash table containing each element, then on subsequent evaluations, we just probe that hash table to determine if there is a match. The planner is in charge of determining when this optimization is possible and it enables it by setting hashfuncid in the ScalarArrayOpExpr. The executor will only perform the hash table evaluation when the hashfuncid is set. This means that not all cases are optimized. For example CHECK constraints containing an IN clause won't go through the planner, so won't get the hashfuncid set. We could maybe do something about that at some later date. The reason we're not doing it now is from fear that we may slow down cases where the expression is evaluated only once. Those cases can be common, for example, a single row INSERT to a table with a CHECK constraint containing an IN clause. In the planner, we enable this when there are suitable hash functions for the ScalarArrayOpExpr's operator and only when there is at least MIN_ARRAY_SIZE_FOR_HASHED_SAOP elements in the array. The threshold is currently set to 9. Author: James Coleman, David Rowley Reviewed-by: David Rowley, Tomas Vondra, Heikki Linnakangas Discussion: https://postgr.es/m/CAAaqYe8x62+=wn0zvNKCj55tPpg-JBHzhZFFc6ANovdqFw7-dA@mail.gmail.com	5 years ago
David Rowley	9eacee2e62	Add Result Cache executor node (take 2) ... Here we add a new executor node type named "Result Cache". The planner can include this node type in the plan to have the executor cache the results from the inner side of parameterized nested loop joins. This allows caching of tuples for sets of parameters so that in the event that the node sees the same parameter values again, it can just return the cached tuples instead of rescanning the inner side of the join all over again. Internally, result cache uses a hash table in order to quickly find tuples that have been previously cached. For certain data sets, this can significantly improve the performance of joins. The best cases for using this new node type are for join problems where a large portion of the tuples from the inner side of the join have no join partner on the outer side of the join. In such cases, hash join would have to hash values that are never looked up, thus bloating the hash table and possibly causing it to multi-batch. Merge joins would have to skip over all of the unmatched rows. If we use a nested loop join with a result cache, then we only cache tuples that have at least one join partner on the outer side of the join. The benefits of using a parameterized nested loop with a result cache increase when there are fewer distinct values being looked up and the number of lookups of each value is large. Also, hash probes to lookup the cache can be much faster than the hash probe in a hash join as it's common that the result cache's hash table is much smaller than the hash join's due to result cache only caching useful tuples rather than all tuples from the inner side of the join. This variation in hash probe performance is more significant when the hash join's hash table no longer fits into the CPU's L3 cache, but the result cache's hash table does. The apparent "random" access of hash buckets with each hash probe can cause a poor L3 cache hit ratio for large hash tables. Smaller hash tables generally perform better. The hash table used for the cache limits itself to not exceeding work_mem * hash_mem_multiplier in size. We maintain a dlist of keys for this cache and when we're adding new tuples and realize we've exceeded the memory budget, we evict cache entries starting with the least recently used ones until we have enough memory to add the new tuples to the cache. For parameterized nested loop joins, we now consider using one of these result cache nodes in between the nested loop node and its inner node. We determine when this might be useful based on cost, which is primarily driven off of what the expected cache hit ratio will be. Estimating the cache hit ratio relies on having good distinct estimates on the nested loop's parameters. For now, the planner will only consider using a result cache for parameterized nested loop joins. This works for both normal joins and also for LATERAL type joins to subqueries. It is possible to use this new node for other uses in the future. For example, to cache results from correlated subqueries. However, that's not done here due to some difficulties obtaining a distinct estimation on the outer plan to calculate the estimated cache hit ratio. Currently we plan the inner plan before planning the outer plan so there is no good way to know if a result cache would be useful or not since we can't estimate the number of times the subplan will be called until the outer plan is generated. The functionality being added here is newly introducing a dependency on the return value of estimate_num_groups() during the join search. Previously, during the join search, we only ever needed to perform selectivity estimations. With this commit, we need to use estimate_num_groups() in order to estimate what the hit ratio on the result cache will be. In simple terms, if we expect 10 distinct values and we expect 1000 outer rows, then we'll estimate the hit ratio to be 99%. Since cache hits are very cheap compared to scanning the underlying nodes on the inner side of the nested loop join, then this will significantly reduce the planner's cost for the join. However, it's fairly easy to see here that things will go bad when estimate_num_groups() incorrectly returns a value that's significantly lower than the actual number of distinct values. If this happens then that may cause us to make use of a nested loop join with a result cache instead of some other join type, such as a merge or hash join. Our distinct estimations have been known to be a source of trouble in the past, so the extra reliance on them here could cause the planner to choose slower plans than it did previous to having this feature. Distinct estimations are also fairly hard to estimate accurately when several tables have been joined already or when a WHERE clause filters out a set of values that are correlated to the expressions we're estimating the number of distinct value for. For now, the costing we perform during query planning for result caches does put quite a bit of faith in the distinct estimations being accurate. When these are accurate then we should generally see faster execution times for plans containing a result cache. However, in the real world, we may find that we need to either change the costings to put less trust in the distinct estimations being accurate or perhaps even disable this feature by default. There's always an element of risk when we teach the query planner to do new tricks that it decides to use that new trick at the wrong time and causes a regression. Users may opt to get the old behavior by turning the feature off using the enable_resultcache GUC. Currently, this is enabled by default. It remains to be seen if we'll maintain that setting for the release. Additionally, the name "Result Cache" is the best name I could think of for this new node at the time I started writing the patch. Nobody seems to strongly dislike the name. A few people did suggest other names but no other name seemed to dominate in the brief discussion that there was about names. Let's allow the beta period to see if the current name pleases enough people. If there's some consensus on a better name, then we can change it before the release. Please see the 2nd discussion link below for the discussion on the "Result Cache" name. Author: David Rowley Reviewed-by: Andy Fan, Justin Pryzby, Zhihong Yu, Hou Zhijie Tested-By: Konstantin Knizhnik Discussion: https://postgr.es/m/CAApHDvrPcQyQdWERGYWx8J%2B2DLUNgXu%2BfOSbQ1UscxrunyXyrQ%40mail.gmail.com Discussion: https://postgr.es/m/CAApHDvq=yQXr5kqhRviT2RhNKwToaWr9JAN5t+5_PzhuRJ3wvg@mail.gmail.com	5 years ago
David Rowley	28b3e3905c	Revert b6002a796 ... This removes "Add Result Cache executor node". It seems that something weird is going on with the tracking of cache hits and misses as highlighted by many buildfarm animals. It's not yet clear what the problem is as other parts of the plan indicate that the cache did work correctly, it's just the hits and misses that were being reported as 0. This is especially a bad time to have the buildfarm so broken, so reverting before too many more animals go red. Discussion: https://postgr.es/m/CAApHDvq_hydhfovm4=izgWs+C5HqEeRScjMbOgbpC-jRAeK3Yw@mail.gmail.com	5 years ago
David Rowley	b6002a796d	Add Result Cache executor node ... Here we add a new executor node type named "Result Cache". The planner can include this node type in the plan to have the executor cache the results from the inner side of parameterized nested loop joins. This allows caching of tuples for sets of parameters so that in the event that the node sees the same parameter values again, it can just return the cached tuples instead of rescanning the inner side of the join all over again. Internally, result cache uses a hash table in order to quickly find tuples that have been previously cached. For certain data sets, this can significantly improve the performance of joins. The best cases for using this new node type are for join problems where a large portion of the tuples from the inner side of the join have no join partner on the outer side of the join. In such cases, hash join would have to hash values that are never looked up, thus bloating the hash table and possibly causing it to multi-batch. Merge joins would have to skip over all of the unmatched rows. If we use a nested loop join with a result cache, then we only cache tuples that have at least one join partner on the outer side of the join. The benefits of using a parameterized nested loop with a result cache increase when there are fewer distinct values being looked up and the number of lookups of each value is large. Also, hash probes to lookup the cache can be much faster than the hash probe in a hash join as it's common that the result cache's hash table is much smaller than the hash join's due to result cache only caching useful tuples rather than all tuples from the inner side of the join. This variation in hash probe performance is more significant when the hash join's hash table no longer fits into the CPU's L3 cache, but the result cache's hash table does. The apparent "random" access of hash buckets with each hash probe can cause a poor L3 cache hit ratio for large hash tables. Smaller hash tables generally perform better. The hash table used for the cache limits itself to not exceeding work_mem * hash_mem_multiplier in size. We maintain a dlist of keys for this cache and when we're adding new tuples and realize we've exceeded the memory budget, we evict cache entries starting with the least recently used ones until we have enough memory to add the new tuples to the cache. For parameterized nested loop joins, we now consider using one of these result cache nodes in between the nested loop node and its inner node. We determine when this might be useful based on cost, which is primarily driven off of what the expected cache hit ratio will be. Estimating the cache hit ratio relies on having good distinct estimates on the nested loop's parameters. For now, the planner will only consider using a result cache for parameterized nested loop joins. This works for both normal joins and also for LATERAL type joins to subqueries. It is possible to use this new node for other uses in the future. For example, to cache results from correlated subqueries. However, that's not done here due to some difficulties obtaining a distinct estimation on the outer plan to calculate the estimated cache hit ratio. Currently we plan the inner plan before planning the outer plan so there is no good way to know if a result cache would be useful or not since we can't estimate the number of times the subplan will be called until the outer plan is generated. The functionality being added here is newly introducing a dependency on the return value of estimate_num_groups() during the join search. Previously, during the join search, we only ever needed to perform selectivity estimations. With this commit, we need to use estimate_num_groups() in order to estimate what the hit ratio on the result cache will be. In simple terms, if we expect 10 distinct values and we expect 1000 outer rows, then we'll estimate the hit ratio to be 99%. Since cache hits are very cheap compared to scanning the underlying nodes on the inner side of the nested loop join, then this will significantly reduce the planner's cost for the join. However, it's fairly easy to see here that things will go bad when estimate_num_groups() incorrectly returns a value that's significantly lower than the actual number of distinct values. If this happens then that may cause us to make use of a nested loop join with a result cache instead of some other join type, such as a merge or hash join. Our distinct estimations have been known to be a source of trouble in the past, so the extra reliance on them here could cause the planner to choose slower plans than it did previous to having this feature. Distinct estimations are also fairly hard to estimate accurately when several tables have been joined already or when a WHERE clause filters out a set of values that are correlated to the expressions we're estimating the number of distinct value for. For now, the costing we perform during query planning for result caches does put quite a bit of faith in the distinct estimations being accurate. When these are accurate then we should generally see faster execution times for plans containing a result cache. However, in the real world, we may find that we need to either change the costings to put less trust in the distinct estimations being accurate or perhaps even disable this feature by default. There's always an element of risk when we teach the query planner to do new tricks that it decides to use that new trick at the wrong time and causes a regression. Users may opt to get the old behavior by turning the feature off using the enable_resultcache GUC. Currently, this is enabled by default. It remains to be seen if we'll maintain that setting for the release. Additionally, the name "Result Cache" is the best name I could think of for this new node at the time I started writing the patch. Nobody seems to strongly dislike the name. A few people did suggest other names but no other name seemed to dominate in the brief discussion that there was about names. Let's allow the beta period to see if the current name pleases enough people. If there's some consensus on a better name, then we can change it before the release. Please see the 2nd discussion link below for the discussion on the "Result Cache" name. Author: David Rowley Reviewed-by: Andy Fan, Justin Pryzby, Zhihong Yu Tested-By: Konstantin Knizhnik Discussion: https://postgr.es/m/CAApHDvrPcQyQdWERGYWx8J%2B2DLUNgXu%2BfOSbQ1UscxrunyXyrQ%40mail.gmail.com Discussion: https://postgr.es/m/CAApHDvq=yQXr5kqhRviT2RhNKwToaWr9JAN5t+5_PzhuRJ3wvg@mail.gmail.com	5 years ago
Tom Lane	86dc90056d	Rework planning and execution of UPDATE and DELETE. ... This patch makes two closely related sets of changes: 1. For UPDATE, the subplan of the ModifyTable node now only delivers the new values of the changed columns (i.e., the expressions computed in the query's SET clause) plus row identity information such as CTID. ModifyTable must re-fetch the original tuple to merge in the old values of any unchanged columns. The core advantage of this is that the changed columns are uniform across all tables of an inherited or partitioned target relation, whereas the other columns might not be. A secondary advantage, when the UPDATE involves joins, is that less data needs to pass through the plan tree. The disadvantage of course is an extra fetch of each tuple to be updated. However, that seems to be very nearly free in context; even worst-case tests don't show it to add more than a couple percent to the total query cost. At some point it might be interesting to combine the re-fetch with the tuple access that ModifyTable must do anyway to mark the old tuple dead; but that would require a good deal of refactoring and it seems it wouldn't buy all that much, so this patch doesn't attempt it. 2. For inherited UPDATE/DELETE, instead of generating a separate subplan for each target relation, we now generate a single subplan that is just exactly like a SELECT's plan, then stick ModifyTable on top of that. To let ModifyTable know which target relation a given incoming row refers to, a tableoid junk column is added to the row identity information. This gets rid of the horrid hack that was inheritance_planner(), eliminating O(N^2) planning cost and memory consumption in cases where there were many unprunable target relations. Point 2 of course requires point 1, so that there is a uniform definition of the non-junk columns to be returned by the subplan. We can't insist on uniform definition of the row identity junk columns however, if we want to keep the ability to have both plain and foreign tables in a partitioning hierarchy. Since it wouldn't scale very far to have every child table have its own row identity column, this patch includes provisions to merge similar row identity columns into one column of the subplan result. In particular, we can merge the whole-row Vars typically used as row identity by FDWs into one column by pretending they are type RECORD. (It's still okay for the actual composite Datums to be labeled with the table's rowtype OID, though.) There is more that can be done to file down residual inefficiencies in this patch, but it seems to be committable now. FDW authors should note several API changes: * The argument list for AddForeignUpdateTargets() has changed, and so has the method it must use for adding junk columns to the query. Call add_row_identity_var() instead of manipulating the parse tree directly. You might want to reconsider exactly what you're adding, too. * PlanDirectModify() must now work a little harder to find the ForeignScan plan node; if the foreign table is part of a partitioning hierarchy then the ForeignScan might not be the direct child of ModifyTable. See postgres_fdw for sample code. * To check whether a relation is a target relation, it's no longer sufficient to compare its relid to root->parse->resultRelation. Instead, check it against all_result_relids or leaf_result_relids, as appropriate. Amit Langote and Tom Lane Discussion: https://postgr.es/m/CA+HiwqHpHdqdDn48yCEhynnniahH78rwcrv1rEX65-fsZGBOLQ@mail.gmail.com	5 years ago
Peter Eisentraut	055fee7eb4	Allow an alias to be attached to a JOIN ... USING ... This allows something like SELECT ... FROM t1 JOIN t2 USING (a, b, c) AS x where x has the columns a, b, c and unlike a regular alias it does not hide the range variables of the tables being joined t1 and t2. Per SQL:2016 feature F404 "Range variable for common column names". Reviewed-by: Vik Fearing <vik.fearing@2ndquadrant.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://www.postgresql.org/message-id/flat/454638cf-d563-ab76-a585-2564428062af@2ndquadrant.com	5 years ago
David Rowley	bb437f995d	Add TID Range Scans to support efficient scanning ranges of TIDs ... This adds a new executor node named TID Range Scan. The query planner will generate paths for TID Range scans when quals are discovered on base relations which search for ranges on the table's ctid column. These ranges may be open at either end. For example, WHERE ctid >= '(10,0)'; will return all tuples on page 10 and over. To support this, two new optional callback functions have been added to table AM. scan_set_tidrange is used to set the scan range to just the given range of TIDs. scan_getnextslot_tidrange fetches the next tuple in the given range. For AMs were scanning ranges of TIDs would not make sense, these functions can be set to NULL in the TableAmRoutine. The query planner won't generate TID Range Scan Paths in that case. Author: Edmund Horner, David Rowley Reviewed-by: David Rowley, Tomas Vondra, Tom Lane, Andres Freund, Zhihong Yu Discussion: https://postgr.es/m/CAMyN-kB-nFTkF=VA_JPwFNo08S0d-Yk0F741S2B7LDmYAi8eyA@mail.gmail.com	5 years ago
Bruce Momjian	ca3b37487b	Update copyright for 2021 ... Backpatch-through: 9.5	5 years ago
Tom Lane	ad77039fad	Calculate extraUpdatedCols in query rewriter, not parser. ... It's unsafe to do this at parse time because addition of generated columns to a table would not invalidate stored rules containing UPDATEs on the table ... but there might now be dependent generated columns that were not there when the rule was made. This also fixes an oversight that rewriteTargetView failed to update extraUpdatedCols when transforming an UPDATE on an updatable view. (Since the new calculation is downstream of that, rewriteTargetView doesn't actually need to do anything; but before, there was a demonstrable bug there.) In v13 and HEAD, this leads to easily-visible bugs because (since commit c6679e4fc) we won't recalculate generated columns that aren't listed in extraUpdatedCols. In v12 this bitmap is mostly just used for trigger-firing decisions, so you'd only notice a problem if a trigger cared whether a generated column had been updated. I'd complained about this back in May, but then forgot about it until bug #16671 from Michael Paul Killian revived the issue. Back-patch to v12 where this field was introduced. If existing stored rules contain any extraUpdatedCols values, they'll be ignored because the rewriter will overwrite them, so the bug will be fixed even for existing rules. (But note that if someone were to update to 13.1 or 12.5, store some rules with UPDATEs on tables having generated columns, and then downgrade to a prior minor version, they might observe issues similar to what this patch fixes. That seems unlikely enough to not be worth going to a lot of effort to fix.) Discussion: https://postgr.es/m/10206.1588964727@sss.pgh.pa.us Discussion: https://postgr.es/m/16671-2fa55851859fb166@postgresql.org	5 years ago
Heikki Linnakangas	178f2d560d	Include result relation info in direct modify ForeignScan nodes. ... FDWs that can perform an UPDATE/DELETE remotely using the "direct modify" set of APIs need to access the ResultRelInfo of the target table. That's currently available in EState.es_result_relation_info, but the next commit will remove that field. This commit adds a new resultRelation field in ForeignScan, to store the target relation's RT index, and the corresponding ResultRelInfo in ForeignScanState. The FDW's PlanDirectModify callback is expected to set 'resultRelation' along with 'operation'. The core code doesn't need them for anything, they are for the convenience of FDW's Begin- and IterateDirectModify callbacks. Authors: Amit Langote, Etsuro Fujita Discussion: https://www.postgresql.org/message-id/CA%2BHiwqGEmiib8FLiHMhKB%2BCH5dRgHSLc5N5wnvc4kym%2BZYpQEQ%40mail.gmail.com	5 years ago
Heikki Linnakangas	1375422c78	Create ResultRelInfos later in InitPlan, index them by RT index. ... Instead of allocating all the ResultRelInfos upfront in one big array, allocate them in ExecInitModifyTable(). es_result_relations is now an array of ResultRelInfo pointers, rather than an array of structs, and it is indexed by the RT index. This simplifies things: we get rid of the separate concept of a "result rel index", and don't need to set it in setrefs.c anymore. This also allows follow-up optimizations (not included in this commit yet) to skip initializing ResultRelInfos for target relations that were not needed at runtime, and removal of the es_result_relation_info pointer. The EState arrays of regular result rels and root result rels are merged into one array. Similarly, the resultRelations and rootResultRelations lists in PlannedStmt are merged into one. It's not actually clear to me why they were kept separate in the first place, but now that the es_result_relations array is indexed by RT index, it certainly seems pointless. The PlannedStmt->resultRelations list is now only needed for ExecRelationIsTargetRelation(). One visible effect of this change is that ExecRelationIsTargetRelation() will now return 'true' also for the partition root, if a partitioned table is updated. That seems like a good thing, although the function isn't used in core code, and I don't see any reason for an FDW to call it on a partition root. Author: Amit Langote Discussion: https://www.postgresql.org/message-id/CA%2BHiwqGEmiib8FLiHMhKB%2BCH5dRgHSLc5N5wnvc4kym%2BZYpQEQ%40mail.gmail.com	5 years ago
Tom Lane	41efb83408	Move resolution of AlternativeSubPlan choices to the planner. ... When commit bd3daddaf introduced AlternativeSubPlans, I had some ambitions towards allowing the choice of subplan to change during execution. That has not happened, or even been thought about, in the ensuing twelve years; so it seems like a failed experiment. So let's rip that out and resolve the choice of subplan at the end of planning (in setrefs.c) rather than during executor startup. This has a number of positive benefits: * Removal of a few hundred lines of executor code, since AlternativeSubPlans need no longer be supported there. * Removal of executor-startup overhead (particularly, initialization of subplans that won't be used). * Removal of incidental costs of having a larger plan tree, such as tree-scanning and copying costs in the plancache; not to mention setrefs.c's own costs of processing the discarded subplans. * EXPLAIN no longer has to print a weird (and undocumented) representation of an AlternativeSubPlan choice; it sees only the subplan actually used. This should mean less confusion for users. * Since setrefs.c knows which subexpression of a plan node it's working on at any instant, it's possible to adjust the estimated number of executions of the subplan based on that. For example, we should usually estimate more executions of a qual expression than a targetlist expression. The implementation used here is pretty simplistic, because we don't want to expend a lot of cycles on the issue; but it's better than ignoring the point entirely, as the executor had to. That last point might possibly result in shifting the choice between hashed and non-hashed EXISTS subplans in a few cases, but in general this patch isn't meant to change planner choices. Since we're doing the resolution so late, it's really impossible to change any plan choices outside the AlternativeSubPlan itself. Patch by me; thanks to David Rowley for review. Discussion: https://postgr.es/m/1992952.1592785225@sss.pgh.pa.us	5 years ago
Tom Lane	fa27dd40d5	Run pgindent with new pg_bsd_indent version 2.1.1. ... Thomas Munro fixed a longstanding annoyance in pg_bsd_indent, that it would misformat lines containing IsA() macros on the assumption that the IsA() call should be treated like a cast. This improves some other cases involving field/variable names that match typedefs, too. The only places that get worse are a couple of uses of the OpenSSL macro STACK_OF(); we'll gladly take that trade-off. Discussion: https://postgr.es/m/20200114221814.GA19630@alvherre.pgsql	5 years ago
Tomas Vondra	d2d8a229bc	Implement Incremental Sort ... Incremental Sort is an optimized variant of multikey sort for cases when the input is already sorted by a prefix of the requested sort keys. For example when the relation is already sorted by (key1, key2) and we need to sort it by (key1, key2, key3) we can simply split the input rows into groups having equal values in (key1, key2), and only sort/compare the remaining column key3. This has a number of benefits: - Reduced memory consumption, because only a single group (determined by values in the sorted prefix) needs to be kept in memory. This may also eliminate the need to spill to disk. - Lower startup cost, because Incremental Sort produce results after each prefix group, which is beneficial for plans where startup cost matters (like for example queries with LIMIT clause). We consider both Sort and Incremental Sort, and decide based on costing. The implemented algorithm operates in two different modes: - Fetching a minimum number of tuples without check of equality on the prefix keys, and sorting on all columns when safe. - Fetching all tuples for a single prefix group and then sorting by comparing only the remaining (non-prefix) keys. We always start in the first mode, and employ a heuristic to switch into the second mode if we believe it's beneficial - the goal is to minimize the number of unnecessary comparions while keeping memory consumption below work_mem. This is a very old patch series. The idea was originally proposed by Alexander Korotkov back in 2013, and then revived in 2017. In 2018 the patch was taken over by James Coleman, who wrote and rewrote most of the current code. There were many reviewers/contributors since 2013 - I've done my best to pick the most active ones, and listed them in this commit message. Author: James Coleman, Alexander Korotkov Reviewed-by: Tomas Vondra, Andreas Karlsson, Marti Raudsepp, Peter Geoghegan, Robert Haas, Thomas Munro, Antonin Houska, Andres Freund, Alexander Kuzmenkov Discussion: https://postgr.es/m/CAPpHfdscOX5an71nHd8WSUH6GNOCf=V7wgDaTXdDd9=goN-gfA@mail.gmail.com Discussion: https://postgr.es/m/CAPpHfds1waRZ=NOmueYq0sx1ZSCnt+5QJvizT8ndT2=etZEeAQ@mail.gmail.com	6 years ago
Tom Lane	9ce77d75c5	Reconsider the representation of join alias Vars. ... The core idea of this patch is to make the parser generate join alias Vars (that is, ones with varno pointing to a JOIN RTE) only when the alias Var is actually different from any raw join input, that is a type coercion and/or COALESCE is necessary to generate the join output value. Otherwise just generate varno/varattno pointing to the relevant join input column. In effect, this means that the planner's flatten_join_alias_vars() transformation is already done in the parser, for all cases except (a) columns that are merged by JOIN USING and are transformed in the process, and (b) whole-row join Vars. In principle that would allow us to skip doing flatten_join_alias_vars() in many more queries than we do now, but we don't have quite enough infrastructure to know that we can do so --- in particular there's no cheap way to know whether there are any whole-row join Vars. I'm not sure if it's worth the trouble to add a Query-level flag for that, and in any case it seems like fit material for a separate patch. But even without skipping the work entirely, this should make flatten_join_alias_vars() faster, particularly where there are nested joins that it previously had to flatten recursively. An essential part of this change is to replace Var nodes' varnoold/varoattno fields with varnosyn/varattnosyn, which have considerably more tightly-defined meanings than the old fields: when they differ from varno/varattno, they identify the Var's position in an aliased JOIN RTE, and the join alias is what ruleutils.c should print for the Var. This is necessary because the varno change destroyed ruleutils.c's ability to find the JOIN RTE from the Var's varno. Another way in which this change broke ruleutils.c is that it's no longer feasible to determine, from a JOIN RTE's joinaliasvars list, which join columns correspond to which columns of the join's immediate input relations. (If those are sub-joins, the joinaliasvars entries may point to columns of their base relations, not the sub-joins.) But that was a horrid mess requiring a lot of fragile assumptions already, so let's just bite the bullet and add some more JOIN RTE fields to make it more straightforward to figure that out. I added two integer-List fields containing the relevant column numbers from the left and right input rels, plus a count of how many merged columns there are. This patch depends on the ParseNamespaceColumn infrastructure that I added in commit 5815696bc. The biggest bit of code change is restructuring transformFromClauseItem's handling of JOINs so that the ParseNamespaceColumn data is propagated upward correctly. Other than that and the ruleutils fixes, everything pretty much just works, though some processing is now inessential. I grabbed two pieces of low-hanging fruit in that line: 1. In find_expr_references, we don't need to recurse into join alias Vars anymore. There aren't any except for references to merged USING columns, which are more properly handled when we scan the join's RTE. This change actually fixes an edge-case issue: we will now record a dependency on any type-coercion function present in a USING column's joinaliasvar, even if that join column has no references in the query text. The odds of the missing dependency causing a problem seem quite small: you'd have to posit somebody dropping an implicit cast between two data types, without removing the types themselves, and then having a stored rule containing a whole-row Var for a join whose USING merge depends on that cast. So I don't feel a great need to change this in the back branches. But in theory this way is more correct. 2. markRTEForSelectPriv and markTargetListOrigin don't need to recurse into join alias Vars either, because the cases they care about don't apply to alias Vars for USING columns that are semantically distinct from the underlying columns. This removes the only case in which markVarForSelectPriv could be called with NULL for the RTE, so adjust the comments to describe that hack as being strictly internal to markRTEForSelectPriv. catversion bump required due to changes in stored rules. Discussion: https://postgr.es/m/7115.1577986646@sss.pgh.pa.us	6 years ago
Bruce Momjian	7559d8ebfa	Update copyrights for 2020 ... Backpatch-through: update all files in master, backpatch legal files through 9.4	6 years ago
Tom Lane	6ef77cf46e	Further adjust EXPLAIN's choices of table alias names. ... This patch causes EXPLAIN to always assign a separate table alias to the parent RTE of an append relation (inheritance set); before, such RTEs were ignored if not actually scanned by the plan. Since the child RTEs now always have that same alias to start with (cf. commit 55a1954da), the net effect is that the parent RTE usually gets the alias used or implied by the query text, and the children all get that alias with "_N" appended. (The exception to "usually" is if there are duplicate aliases in different subtrees of the original query; then some of those original RTEs will also have "_N" appended.) This results in more uniform output for partitioned-table plans than we had before: the partitioned table itself gets the original alias, and all child tables have aliases with "_N", rather than the previous behavior where one of the children would get an alias without "_N". The reason for giving the parent RTE an alias, even if it isn't scanned by the plan, is that we now use the parent's alias to qualify Vars that refer to an appendrel output column and appear above the Append or MergeAppend that computes the appendrel. But below the append, Vars refer to some one of the child relations, and are displayed that way. This seems clearer than the old behavior where a Var that could carry values from any child relation was displayed as if it referred to only one of them. While at it, change ruleutils.c so that the code paths used by EXPLAIN deal in Plan trees not PlanState trees. This effectively reverts a decision made in commit 1cc29fe7c, which seemed like a good idea at the time to make ruleutils.c consistent with explain.c. However, it's problematic because we'd really like to allow executor startup pruning to remove all the children of an append node when possible, leaving no child PlanState to resolve Vars against. (That's not done here, but will be in the next patch.) This requires different handling of subplans and initplans than before, but is otherwise a pretty straightforward change. Discussion: https://postgr.es/m/001001d4f44b$2a2cca50$7e865ef0$@lab.ntt.co.jp	6 years ago
Tom Lane	5ee190f8ec	Rationalize use of list_concat + list_copy combinations. ... In the wake of commit 1cff1b95a, the result of list_concat no longer shares the ListCells of the second input. Therefore, we can replace "list_concat(x, list_copy(y))" with just "list_concat(x, y)". To improve call sites that were list_copy'ing the first argument, or both arguments, invent "list_concat_copy()" which produces a new list sharing no ListCells with either input. (This is a bit faster than "list_concat(list_copy(x), y)" because it makes the result list the right size to start with.) In call sites that were not list_copy'ing the second argument, the new semantics mean that we are usually leaking the second List's storage, since typically there is no remaining pointer to it. We considered inventing another list_copy variant that would list_free the second input, but concluded that for most call sites it isn't worth worrying about, given the relative compactness of the new List representation. (Note that in cases where such leakage would happen, the old code already leaked the second List's header; so we're only discussing the size of the leak not whether there is one. I did adjust two or three places that had been troubling to free that header so that they manually free the whole second List.) Patch by me; thanks to David Rowley for review. Discussion: https://postgr.es/m/11587.1550975080@sss.pgh.pa.us	6 years ago
Andres Freund	2abd7ae9b2	Fix representation of hash keys in Hash/HashJoin nodes. ... In 5f32b29c18 I changed the creation of HashState.hashkeys to actually use HashState as the parent (instead of HashJoinState, which was incorrect, as they were executed below HashState), to fix the problem of hashkeys expressions otherwise relying on slot types appropriate for HashJoinState, rather than HashState as would be correct. That reliance was only introduced in 12, which is why it previously worked to use HashJoinState as the parent (although I'd be unsurprised if there were problematic cases). Unfortunately that's not a sufficient solution, because before this commit, the to-be-hashed expressions referenced inner/outer as appropriate for the HashJoin, not Hash. That didn't have obvious bad consequences, because the slots containing the tuples were put into ecxt_innertuple when hashing a tuple for HashState (even though Hash doesn't have an inner plan). There are less common cases where this can cause visible problems however (rather than just confusion when inspecting such executor trees). E.g. "ERROR: bogus varno: 65000", when explaining queries containing a HashJoin where the subsidiary Hash node's hash keys reference a subplan. While normally hashkeys aren't displayed by EXPLAIN, if one of those expressions references a subplan, that subplan may be printed as part of the Hash node - which then failed because an inner plan was referenced, and Hash doesn't have that. It seems quite possible that there's other broken cases, too. Fix the problem by properly splitting the expression for the HashJoin and Hash nodes at plan time, and have them reference the proper subsidiary node. While other workarounds are possible, fixing this correctly seems easy enough. It was a pretty ugly hack to have ExecInitHashJoin put the expression into the already initialized HashState, in the first place. I decided to not just split inner/outer hashkeys inside make_hashjoin(), but also to separate out hashoperators and hashcollations at plan time. Otherwise we would have ended up having two very similar loops, one at plan time and the other during executor startup. The work seems to more appropriately belong to plan time, anyway. Reported-By: Nikita Glukhov, Alexander Korotkov Author: Andres Freund Reviewed-By: Tom Lane, in an earlier version Discussion: https://postgr.es/m/CAPpHfdvGVegF_TKKRiBrSmatJL2dR9uwFCuR+teQ_8tEXU8mxg@mail.gmail.com Backpatch: 12-	6 years ago
Tom Lane	8255c7a5ee	Phase 2 pgindent run for v12. ... Switch to 2.1 version of pg_bsd_indent. This formats multiline function declarations "correctly", that is with additional lines of parameter declarations indented to match where the first line's left parenthesis is. Discussion: https://postgr.es/m/CAEepm=0P3FeTXRcU5B2W3jv3PgRVZ-kGUXLGfd42FFhUROO3ug@mail.gmail.com	6 years ago
Tom Lane	8edd0e7946	Suppress Append and MergeAppend plan nodes that have a single child. ... If there's only one child relation, the Append or MergeAppend isn't doing anything useful, and can be elided. It does have a purpose during planning though, which is to serve as a buffer between parent and child Var numbering. Therefore we keep it all the way through to setrefs.c, and get rid of it only after fixing references in the plan level(s) above it. This works largely the same as setrefs.c's ancient hack to get rid of no-op SubqueryScan nodes, and can even share some code with that. Note the change to make setrefs.c use apply_tlist_labeling rather than ad-hoc code. This has the effect of propagating the child's resjunk and ressortgroupref labels, which formerly weren't propagated when removing a SubqueryScan. Doing that is demonstrably necessary for the [Merge]Append cases, and seems harmless for SubqueryScan, if only because trivial_subqueryscan is afraid to collapse cases where the resjunk marking differs. (I suspect that restriction could now be removed, though it's unclear that it'd make any new matches possible, since the outer query can't have references to a child resjunk column.) David Rowley, reviewed by Alvaro Herrera and Tomas Vondra Discussion: https://postgr.es/m/CAKJS1f_7u8ATyJ1JGTMHFoKDvZdeF-iEBhs+sM_SXowOr9cArg@mail.gmail.com	7 years ago
Tom Lane	f09346a9c6	Refactor planner's header files. ... Create a new header optimizer/optimizer.h, which exposes just the planner functions that can be used "at arm's length", without need to access Paths or the other planner-internal data structures defined in nodes/relation.h. This is intended to provide the whole planner API seen by most of the rest of the system; although FDWs still need to use additional stuff, and more thought is also needed about just what selfuncs.c should rely on. The main point of doing this now is to limit the amount of new #include baggage that will be needed by "planner support functions", which I expect to introduce later, and which will be in relevant datatype modules rather than anywhere near the planner. This commit just moves relevant declarations into optimizer.h from other header files (a couple of which go away because everything got moved), and adjusts #include lists to match. There's further cleanup that could be done if we want to decide that some stuff being exposed by optimizer.h doesn't belong in the planner at all, but I'll leave that for another day. Discussion: https://postgr.es/m/11460.1548706639@sss.pgh.pa.us	7 years ago
Tom Lane	18c0da88a5	Split QTW_EXAMINE_RTES flag into QTW_EXAMINE_RTES_BEFORE/_AFTER. ... This change allows callers of query_tree_walker() to choose whether to visit an RTE before or after visiting the contents of the RTE (i.e., prefix or postfix tree order). All existing users of QTW_EXAMINE_RTES want the QTW_EXAMINE_RTES_BEFORE behavior, but an upcoming patch will want QTW_EXAMINE_RTES_AFTER, and it seems like a potentially useful change on its own. Andreas Karlsson (extracted from CTE inlining patch) Discussion: https://postgr.es/m/8810.1542402910@sss.pgh.pa.us	7 years ago
Tom Lane	eaf0380ecc	Fix C++ compile failures in headers. ... Avoid using "typeid" as a parameter name in header files, since that is a C++ keyword. These cases were introduced recently, in 04fe805a1 and 586b98fdf. Since I'm an incurable neatnik, also rename these parameters in the underlying function definitions. That's not really necessary per project rules, but I don't like function declarations that don't quite agree with the underlying definitions. Per src/tools/pginclude/cpluspluscheck.	7 years ago
Bruce Momjian	97c39498e5	Update copyright for 2019 ... Backpatch-through: certain files through 9.4	7 years ago
Tom Lane	04fe805a17	Drop no-op CoerceToDomain nodes from expressions at planning time. ... If a domain has no constraints, then CoerceToDomain doesn't really do anything and can be simplified to a RelabelType. This not only eliminates cycles at execution, but allows the planner to optimize better (for instance, match the coerced expression to an index on the underlying column). However, we do have to support invalidating the plan later if a constraint gets added to the domain. That's comparable to the case of a change to a SQL function that had been inlined into a plan, so all the necessary logic already exists for plans depending on functions. We need only duplicate or share that logic for domains. ALTER DOMAIN ADD/DROP CONSTRAINT need to be taught to send out sinval messages for the domain's pg_type entry, since those operations don't update that row. (ALTER DOMAIN SET/DROP NOT NULL do update that row, so no code change is needed for them.) Testing this revealed what's really a pre-existing bug in plpgsql: it caches the SQL-expression-tree expansion of type coercions and had no provision for invalidating entries in that cache. Up to now that was only a problem if such an expression had inlined a SQL function that got changed, which is unlikely though not impossible. But failing to track changes of domain constraints breaks an existing regression test case and would likely cause practical problems too. We could fix that locally in plpgsql, but what seems like a better idea is to build some generic infrastructure in plancache.c to store standalone expressions and track invalidation events for them. (It's tempting to wonder whether plpgsql's "simple expression" stuff could use this code with lower overhead than its current use of the heavyweight plancache APIs. But I've left that idea for later.) Other stuff fixed in passing: * Allow estimate_expression_value() to drop CoerceToDomain unconditionally, effectively assuming that the coercion will succeed. This will improve planner selectivity estimates for cases involving estimatable expressions that are coerced to domains. We could have done this independently of everything else here, but there wasn't previously any need for eval_const_expressions_mutator to know about CoerceToDomain at all. * Use a dlist for plancache.c's list of cached plans, rather than a manually threaded singly-linked list. That eliminates a potential performance problem in DropCachedPlan. * Fix a couple of inconsistencies in typecmds.c about whether operations on domains drop RowExclusiveLock on pg_type. Our common practice is that DDL operations do drop catalog locks, so standardize on that choice. Discussion: https://postgr.es/m/19958.1544122124@sss.pgh.pa.us	7 years ago
Tom Lane	0f7ec8d9c3	Repair bogus handling of multi-assignment Params in upper plan levels. ... Our support for multiple-set-clauses in UPDATE assumes that the Params referencing a MULTIEXPR_SUBLINK SubPlan will appear before that SubPlan in the targetlist of the plan node that calculates the updated row. (Yeah, it's a hack...) In some PG branches it's possible that a Result node gets inserted between the primary calculation of the update tlist and the ModifyTable node. setrefs.c did the wrong thing in this case and left the upper-level Params as Params, causing a crash at runtime. What it should do is replace them with "outer" Vars referencing the child plan node's output. That's a result of careless ordering of operations in fix_upper_expr_mutator, so we can fix it just by reordering the code. Fix fix_join_expr_mutator similarly for consistency, even though join nodes could never appear in such a context. (In general, it seems likely to be a bit cheaper to use Vars than Params in such situations anyway, so this patch might offer a tiny performance improvement.) The hazard extends back to 9.5 where the MULTIEXPR_SUBLINK stuff was introduced, so back-patch that far. However, this may be a live bug only in 9.6.x and 10.x, as the other branches don't seem to want to calculate the final tlist below the Result node. (That plan shape change between branches might be a mini-bug in itself, but I'm not really interested in digging into the reasons for that right now. Still, add a regression test memorializing what we expect there, so we'll notice if it changes again.) Per bug report from Eduards Bezverhijs. Discussion: https://postgr.es/m/b6cd572a-3e44-8785-75e9-c512a5a17a73@tieto.com	7 years ago
Tom Lane	52ed730d51	Remove some unnecessary fields from Plan trees. ... In the wake of commit f2343653f, we no longer need some fields that were used before to control executor lock acquisitions: * PlannedStmt.nonleafResultRelations can go away entirely. * partitioned_rels can go away from Append, MergeAppend, and ModifyTable. However, ModifyTable still needs to know the RT index of the partition root table if any, which was formerly kept in the first entry of that list. Add a new field "rootRelation" to remember that. rootRelation is partly redundant with nominalRelation, in that if it's set it will have the same value as nominalRelation. However, the latter field has a different purpose so it seems best to keep them distinct. Amit Langote, reviewed by David Rowley and Jesper Pedersen, and whacked around a bit more by me Discussion: https://postgr.es/m/468c85d9-540e-66a2-1dde-fec2b741e688@lab.ntt.co.jp	7 years ago
Tom Lane	9ddef36278	Centralize executor's opening/closing of Relations for rangetable entries. ... Create an array estate->es_relations[] paralleling the es_range_table, and store references to Relations (relcache entries) there, so that any given RT entry is opened and closed just once per executor run. Scan nodes typically still call ExecOpenScanRelation, but ExecCloseScanRelation is no more; relation closing is now done centrally in ExecEndPlan. This is slightly more complex than one would expect because of the interactions with relcache references held in ResultRelInfo nodes. The general convention is now that ResultRelInfo->ri_RelationDesc does not represent a separate relcache reference and so does not need to be explicitly closed; but there is an exception for ResultRelInfos in the es_trig_target_relations list, which are manufactured by ExecGetTriggerResultRel and have to be cleaned up by ExecCleanUpTriggerState. (That much was true all along, but these ResultRelInfos are now more different from others than they used to be.) To allow the partition pruning logic to make use of es_relations[] rather than having its own relcache references, adjust PartitionedRelPruneInfo to store an RT index rather than a relation OID. Amit Langote, reviewed by David Rowley and Jesper Pedersen, some mods by me Discussion: https://postgr.es/m/468c85d9-540e-66a2-1dde-fec2b741e688@lab.ntt.co.jp	7 years ago
Etsuro Fujita	7cfdc77023	Disable support for partitionwise joins in problematic cases. ... Commit f49842d, which added support for partitionwise joins, built the child's tlist by applying adjust_appendrel_attrs() to the parent's. So in the case where the parent's included a whole-row Var for the parent, the child's contained a ConvertRowtypeExpr. To cope with that, that commit added code to the planner, such as setrefs.c, but some code paths still assumed that the tlist for a scan (or join) rel would only include Vars and PlaceHolderVars, which was true before that commit, causing errors: * When creating an explicit sort node for an input path for a mergejoin path for a child join, prepare_sort_from_pathkeys() threw the 'could not find pathkey item to sort' error. * When deparsing a relation participating in a pushed down child join as a subquery in contrib/postgres_fdw, get_relation_column_alias_ids() threw the 'unexpected expression in subquery output' error. * When performing set_plan_references() on a local join plan generated by contrib/postgres_fdw for EvalPlanQual support for a pushed down child join, fix_join_expr() threw the 'variable not found in subplan target lists' error. To fix these, two approaches have been proposed: one by Ashutosh Bapat and one by me. While the former keeps building the child's tlist with a ConvertRowtypeExpr, the latter builds it with a whole-row Var for the child not to violate the planner assumption, and tries to fix it up later, But both approaches need more work, so refuse to generate partitionwise join paths when whole-row Vars are involved, instead. We don't need to handle ConvertRowtypeExprs in the child's tlists for now, so this commit also removes the changes to the planner. Previously, partitionwise join computed attr_needed data for each child separately, and built the child join's tlist using that data, which also required an extra step for adding PlaceHolderVars to that tlist, but it would be more efficient to build it from the parent join's tlist through the adjust_appendrel_attrs() transformation. So this commit builds that list that way, and simplifies build_joinrel_tlist() and placeholder.c as well as part of set_append_rel_size() to basically what they were before partitionwise join went in. Back-patch to PG11 where partitionwise join was introduced. Report by Rajkumar Raghuwanshi. Analysis by Ashutosh Bapat, who also provided some of regression tests. Patch by me, reviewed by Robert Haas. Discussion: https://postgr.es/m/CAKcux6ktu-8tefLWtQuuZBYFaZA83vUzuRd7c1YHC-yEWyYFpg@mail.gmail.com	7 years ago
Simon Riggs	08ea7a2291	Revert MERGE patch ... This reverts commits d204ef6377, 83454e3c2b and a few more commits thereafter (complete list at the end) related to MERGE feature. While the feature was fully functional, with sufficient test coverage and necessary documentation, it was felt that some parts of the executor and parse-analyzer can use a different design and it wasn't possible to do that in the available time. So it was decided to revert the patch for PG11 and retry again in the future. Thanks again to all reviewers and bug reporters. List of commits reverted, in reverse chronological order: f1464c5380 Improve parse representation for MERGE ddb4158579 MERGE syntax diagram correction 530e69e59b Allow cpluspluscheck to pass by renaming variable 01b88b4df5 MERGE minor errata 3af7b2b0d4 MERGE fix variable warning in non-assert builds a5d86181ec MERGE INSERT allows only one VALUES clause 4b2d44031f MERGE post-commit review 4923550c20 Tab completion for MERGE aa3faa3c7a WITH support in MERGE 83454e3c2b New files for MERGE d204ef6377 MERGE SQL Command following SQL:2016 Author: Pavan Deolasee Reviewed-by: Michael Paquier	8 years ago
Simon Riggs	4b2d44031f	MERGE post-commit review ... Review comments from Andres Freund * Consolidate code into AfterTriggerGetTransitionTable() * Rename nodeMerge.c to execMerge.c * Rename nodeMerge.h to execMerge.h * Move MERGE handling in ExecInitModifyTable() into a execMerge.c ExecInitMerge() * Move mt_merge_subcommands flags into execMerge.h * Rename opt_and_condition to opt_merge_when_and_condition * Wordsmith various comments Author: Pavan Deolasee Reviewer: Simon Riggs	8 years ago
Simon Riggs	d204ef6377	MERGE SQL Command following SQL:2016 ... 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 other require multiple PL statements. e.g. 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 and partitioned tables, including column and row security enforcement, as well as support for row, statement and transition triggers. 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 statically from PL/pgSQL. MERGE does not yet support inheritance, write rules, RETURNING clauses, updatable views or foreign tables. MERGE follows SQL Standard per the most recent SQL:2016. Includes full tests and documentation, including full isolation tests to demonstrate the concurrent behavior. This version written from scratch in 2017 by Simon Riggs, using docs and tests originally written in 2009. Later work from Pavan Deolasee has been both complex and deep, leaving the lead author credit now in his hands. Extensive discussion of concurrency from Peter Geoghegan, with thanks for the time and effort contributed. Various issues reported via sqlsmith by Andreas Seltenreich Authors: Pavan Deolasee, Simon Riggs Reviewer: Peter Geoghegan, Amit Langote, Tomas Vondra, Simon Riggs Discussion: https://postgr.es/m/CANP8+jKitBSrB7oTgT9CY2i1ObfOt36z0XMraQc+Xrz8QB0nXA@mail.gmail.com https://postgr.es/m/CAH2-WzkJdBuxj9PO=2QaO9-3h3xGbQPZ34kJH=HukRekwM-GZg@mail.gmail.com	8 years ago
Simon Riggs	7cf8a5c302	Revert "Modified files for MERGE" ... This reverts commit 354f13855e.	8 years ago
Simon Riggs	354f13855e	Modified files for MERGE	8 years ago
Alvaro Herrera	1b89c2188b	Fix typo	8 years ago
Bruce Momjian	9d4649ca49	Update copyright for 2018 ... Backpatch-through: certain files through 9.3	8 years ago
Robert Haas	eaedf0df71	Update typedefs.list and re-run pgindent ... Discussion: http://postgr.es/m/CA+TgmoaA9=1RWKtBWpDaj+sF3Stgc8sHgf5z=KGtbjwPLQVDMA@mail.gmail.com	8 years ago
Robert Haas	e89a71fb44	Pass InitPlan values to workers via Gather (Merge). ... If a PARAM_EXEC parameter is used below a Gather (Merge) but the InitPlan that computes it is attached to or above the Gather (Merge), force the value to be computed before starting parallelism and pass it down to all workers. This allows us to use parallelism in cases where it previously would have had to be rejected as unsafe. We do - in this case - lose the optimization that the value is only computed if it's actually used. An alternative strategy would be to have the first worker that needs the value compute it, but one downside of that approach is that we'd then need to select a parallel-safe path to compute the parameter value; it couldn't for example contain a Gather (Merge) node. At some point in the future, we might want to consider both approaches. Independent of that consideration, there is a great deal more work that could be done to make more kinds of PARAM_EXEC parameters parallel-safe. This infrastructure could be used to allow a Gather (Merge) on the inner side of a nested loop (although that's not a very appealing plan) and cases where the InitPlan is attached below the Gather (Merge) could be addressed as well using various techniques. But this is a good start. Amit Kapila, reviewed and revised by me. Reviewing and testing from Kuntal Ghosh, Haribabu Kommi, and Tushar Ahuja. Discussion: http://postgr.es/m/CAA4eK1LV0Y1AUV4cUCdC+sYOx0Z0-8NAJ2Pd9=UKsbQ5Sr7+JQ@mail.gmail.com	8 years ago
Tom Lane	08f1e1f0a4	Make setrefs.c match by ressortgroupref even for plain Vars. ... Previously, we skipped using search_indexed_tlist_for_sortgroupref() if the tlist expression being sought in the child plan node was merely a Var. This is purely an optimization, based on the theory that search_indexed_tlist_for_var() is faster, and one copy of a Var should be as good as another. However, the GROUPING SETS patch broke the latter assumption: grouping columns containing the "same" Var can sometimes have different outputs, as shown in the test case added here. So do it the hard way whenever a ressortgroupref marking exists. (If this seems like a bottleneck, we could imagine building a tlist index data structure for ressortgroupref values, as we do for Vars. But I'll let that idea go until there's some evidence it's worthwhile.) Back-patch to 9.6. The problem also exists in 9.5 where GROUPING SETS came in, but this patch is insufficient to resolve the problem in 9.5: there is some obscure dependency on the upper-planner-pathification work that happened in 9.6. Given that this is such a weird corner case, and no end users have complained about it, it doesn't seem worth the work to develop a fix for 9.5. Patch by me, per a report from Heikki Linnakangas. (This does not fix Heikki's original complaint, just the follow-on one.) Discussion: https://postgr.es/m/aefc657e-edb2-64d5-6df1-a0828f6e9104@iki.fi	8 years ago
Robert Haas	f49842d1ee	Basic partition-wise join functionality. ... Instead of joining two partitioned tables in their entirety we can, if it is an equi-join on the partition keys, join the matching partitions individually. This involves teaching the planner about "other join" rels, which are related to regular join rels in the same way that other member rels are related to baserels. This can use significantly more CPU time and memory than regular join planning, because there may now be a set of "other" rels not only for every base relation but also for every join relation. In most practical cases, this probably shouldn't be a problem, because (1) it's probably unusual to join many tables each with many partitions using the partition keys for all joins and (2) if you do that scenario then you probably have a big enough machine to handle the increased memory cost of planning and (3) the resulting plan is highly likely to be better, so what you spend in planning you'll make up on the execution side. All the same, for now, turn this feature off by default. Currently, we can only perform joins between two tables whose partitioning schemes are absolutely identical. It would be nice to cope with other scenarios, such as extra partitions on one side or the other with no match on the other side, but that will have to wait for a future patch. Ashutosh Bapat, reviewed and tested by Rajkumar Raghuwanshi, Amit Langote, Rafia Sabih, Thomas Munro, Dilip Kumar, Antonin Houska, Amit Khandekar, and by me. A few final adjustments by me. Discussion: http://postgr.es/m/CAFjFpRfQ8GrQvzp3jA2wnLqrHmaXna-urjm_UY9BqXj=EaDTSA@mail.gmail.com Discussion: http://postgr.es/m/CAFjFpRcitjfrULr5jfuKWRPsGUX0LQ0k8-yG0Qw2+1LBGNpMdw@mail.gmail.com	8 years ago
Tom Lane	c12d570fa1	Support arrays over domains. ... Allowing arrays with a domain type as their element type was left un-done in the original domain patch, but not for any very good reason. This omission leads to such surprising results as array_agg() not working on a domain column, because the parser can't identify a suitable output type for the polymorphic aggregate. In order to fix this, first clean up the APIs of coerce_to_domain() and some internal functions in parse_coerce.c so that we consistently pass around a CoercionContext along with CoercionForm. Previously, we sometimes passed an "isExplicit" boolean flag instead, which is strictly less information; and coerce_to_domain() didn't even get that, but instead had to reverse-engineer isExplicit from CoercionForm. That's contrary to the documentation in primnodes.h that says that CoercionForm only affects display and not semantics. I don't think this change fixes any live bugs, but it makes things more consistent. The main reason for doing it though is that now build_coercion_expression() receives ccontext, which it needs in order to be able to recursively invoke coerce_to_target_type(). Next, reimplement ArrayCoerceExpr so that the node does not directly know any details of what has to be done to the individual array elements while performing the array coercion. Instead, the per-element processing is represented by a sub-expression whose input is a source array element and whose output is a target array element. This simplifies life in parse_coerce.c, because it can build that sub-expression by a recursive invocation of coerce_to_target_type(). The executor now handles the per-element processing as a compiled expression instead of hard-wired code. The main advantage of this is that we can use a single ArrayCoerceExpr to handle as many as three successive steps per element: base type conversion, typmod coercion, and domain constraint checking. The old code used two stacked ArrayCoerceExprs to handle type + typmod coercion, which was pretty inefficient, and adding yet another array deconstruction to do domain constraint checking seemed very unappetizing. In the case where we just need a single, very simple coercion function, doing this straightforwardly leads to a noticeable increase in the per-array-element runtime cost. Hence, add an additional shortcut evalfunc in execExprInterp.c that skips unnecessary overhead for that specific form of expression. The runtime speed of simple cases is within 1% or so of where it was before, while cases that previously required two levels of array processing are significantly faster. Finally, create an implicit array type for every domain type, as we do for base types, enums, etc. Everything except the array-coercion case seems to just work without further effort. Tom Lane, reviewed by Andrew Dunstan Discussion: https://postgr.es/m/9852.1499791473@sss.pgh.pa.us	8 years ago
Tom Lane	382ceffdf7	Phase 3 of pgindent updates. ... Don't move parenthesized lines to the left, even if that means they flow past the right margin. By default, BSD indent lines up statement continuation lines that are within parentheses so that they start just to the right of the preceding left parenthesis. However, traditionally, if that resulted in the continuation line extending to the right of the desired right margin, then indent would push it left just far enough to not overrun the margin, if it could do so without making the continuation line start to the left of the current statement indent. That makes for a weird mix of indentations unless one has been completely rigid about never violating the 80-column limit. This behavior has been pretty universally panned by Postgres developers. Hence, disable it with indent's new -lpl switch, so that parenthesized lines are always lined up with the preceding left paren. This patch is much less interesting than the first round of indent changes, but also bulkier, so I thought it best to separate the effects. Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us	8 years ago
Tom Lane	c7b8998ebb	Phase 2 of pgindent updates. ... Change pg_bsd_indent to follow upstream rules for placement of comments to the right of code, and remove pgindent hack that caused comments following #endif to not obey the general rule. Commit e3860ffa4d wasn't actually using the published version of pg_bsd_indent, but a hacked-up version that tried to minimize the amount of movement of comments to the right of code. The situation of interest is where such a comment has to be moved to the right of its default placement at column 33 because there's code there. BSD indent has always moved right in units of tab stops in such cases --- but in the previous incarnation, indent was working in 8-space tab stops, while now it knows we use 4-space tabs. So the net result is that in about half the cases, such comments are placed one tab stop left of before. This is better all around: it leaves more room on the line for comment text, and it means that in such cases the comment uniformly starts at the next 4-space tab stop after the code, rather than sometimes one and sometimes two tabs after. Also, ensure that comments following #endif are indented the same as comments following other preprocessor commands such as #else. That inconsistency turns out to have been self-inflicted damage from a poorly-thought-through post-indent "fixup" in pgindent. This patch is much less interesting than the first round of indent changes, but also bulkier, so I thought it best to separate the effects. Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us	8 years ago
Bruce Momjian	a6fd7b7a5f	Post-PG 10 beta1 pgindent run ... perltidy run not included.	8 years ago