On Fri, Jan 16, 2026 at 11:49 AM Corey Huinker <[email protected]> wrote:
> Assuming following conditions to be true >> 1. object on the other side usually has statistics >> 2. it didn't when we queried. >> >> The reason for that situation is that the object was not analyzed >> before for the reasons you mention. Then why not just run ANALYZE and >> instantiate the statistics. That will happen only rarely. > > > I agree. > > >> Why do we >> need a table and server option to control that behaviour? Maybe you >> have already explained and I am not able to understand your answer. >> > > I probably didn't explain it, but one reason for having the option is that > the role used to connect to the remote database might not have the > permissions to analyze tables in general, or that table in particular. > Changes in this release, aside from rebasing: - The generic analyze and fdw.h changes are in their own patch (0001) that ignores contrib/postgres_fdw entirely. - The option for remote_analyze has been moved to its own patch (0003). - The errors raised are now warnings, to ensure that we can always fall back to row sampling. - All local attributes with attstatarget > 0 must get matching remote statistics or the import is considered a failure. - The pg_restore_attribute_stats() call has been turned into a prepared statement, for clarity and some minor parsing savings. - The calls to pg_restore_relation_stats() are parameterized, but not prepared as this is rarely called more than once. - postgresStatisticsAreImportable will now disqualify a table if has extended statistics objects, because we can't compute those without a row sample.
From 7b695148065be8d3456ebb0af92cf3f93fc6ae10 Mon Sep 17 00:00:00 2001 From: Corey Huinker <[email protected]> Date: Sat, 17 Jan 2026 16:39:45 -0500 Subject: [PATCH v10 1/3] Add FDW functions for importing optimizer statistics. Add the the function StatisticsAreImportable which is used as a lightweight preliminary scan to determine if the remote table could potentially have statistics that could be imported instead of fetching a row sample from the remote table, which can be expensive. Also add the function ImportStatistics which attempts to actually fetch those statistics from the remote server, and if successful import them into the local statistics catalog. --- src/include/foreign/fdwapi.h | 8 ++++ src/backend/commands/analyze.c | 68 ++++++++++++++++++++++++---------- 2 files changed, 56 insertions(+), 20 deletions(-) diff --git a/src/include/foreign/fdwapi.h b/src/include/foreign/fdwapi.h index 96b6f692d2a..59beeae4f45 100644 --- a/src/include/foreign/fdwapi.h +++ b/src/include/foreign/fdwapi.h @@ -157,6 +157,12 @@ typedef bool (*AnalyzeForeignTable_function) (Relation relation, AcquireSampleRowsFunc *func, BlockNumber *totalpages); +typedef bool (*StatisticsAreImportable_function) (Relation relation); + +typedef bool (*ImportStatistics_function) (Relation relation, + List *va_cols, + int elevel); + typedef List *(*ImportForeignSchema_function) (ImportForeignSchemaStmt *stmt, Oid serverOid); @@ -255,6 +261,8 @@ typedef struct FdwRoutine /* Support functions for ANALYZE */ AnalyzeForeignTable_function AnalyzeForeignTable; + StatisticsAreImportable_function StatisticsAreImportable; + ImportStatistics_function ImportStatistics; /* Support functions for IMPORT FOREIGN SCHEMA */ ImportForeignSchema_function ImportForeignSchema; diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c index a483424152c..c84367461fb 100644 --- a/src/backend/commands/analyze.c +++ b/src/backend/commands/analyze.c @@ -113,6 +113,9 @@ analyze_rel(Oid relid, RangeVar *relation, int elevel; AcquireSampleRowsFunc acquirefunc = NULL; BlockNumber relpages = 0; + FdwRoutine *fdwroutine = NULL; + bool can_import_stats = false; + bool stats_imported = false; /* Select logging level */ if (params.options & VACOPT_VERBOSE) @@ -195,27 +198,16 @@ analyze_rel(Oid relid, RangeVar *relation, else if (onerel->rd_rel->relkind == RELKIND_FOREIGN_TABLE) { /* - * For a foreign table, call the FDW's hook function to see whether it - * supports analysis. + * For a foreign table, call the FDW's hook functions to see whether + * it supports statistics import or analysis. */ - FdwRoutine *fdwroutine; - bool ok = false; fdwroutine = GetFdwRoutineForRelation(onerel, false); - if (fdwroutine->AnalyzeForeignTable != NULL) - ok = fdwroutine->AnalyzeForeignTable(onerel, - &acquirefunc, - &relpages); - - if (!ok) - { - ereport(WARNING, - (errmsg("skipping \"%s\" --- cannot analyze this foreign table", - RelationGetRelationName(onerel)))); - relation_close(onerel, ShareUpdateExclusiveLock); - return; - } + if (fdwroutine->ImportStatistics != NULL && + fdwroutine->StatisticsAreImportable != NULL && + fdwroutine->StatisticsAreImportable(onerel)) + can_import_stats = true; } else if (onerel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE) { @@ -247,10 +239,46 @@ analyze_rel(Oid relid, RangeVar *relation, PROGRESS_ANALYZE_STARTED_BY_MANUAL); /* - * Do the normal non-recursive ANALYZE. We can skip this for partitioned - * tables, which don't contain any rows. + * If this table can import statistics, attempt to do so. */ - if (onerel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE) + if (can_import_stats) + { + Assert(onerel->rd_rel->relkind == RELKIND_FOREIGN_TABLE); + Assert(fdwroutine != NULL); + Assert(fdwroutine->ImportStatistics != NULL); + stats_imported = fdwroutine->ImportStatistics(onerel, va_cols, elevel); + } + + /* + * Foreign tables that were not able to import stats will resort to + * regular sampling. + */ + if ((onerel->rd_rel->relkind == RELKIND_FOREIGN_TABLE) + && !stats_imported) + { + bool ok = false; + + if (fdwroutine->AnalyzeForeignTable != NULL) + ok = fdwroutine->AnalyzeForeignTable(onerel, + &acquirefunc, + &relpages); + + if (!ok) + { + ereport(WARNING, + errmsg("skipping \"%s\" -- cannot analyze this foreign table.", + RelationGetRelationName(onerel))); + relation_close(onerel, ShareUpdateExclusiveLock); + return; + } + } + + /* + * Do the normal non-recursive ANALYZE. We can skip this for partitioned + * tables and foreign tables that successfully imported statistics. + */ + if ((onerel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE) + && !stats_imported) do_analyze_rel(onerel, params, va_cols, acquirefunc, relpages, false, in_outer_xact, elevel); base-commit: 6831cd9e3b082d7b830c3196742dd49e3540c49b -- 2.52.0
From 7de88b6864124f52a497cf123b2b23836401b985 Mon Sep 17 00:00:00 2001 From: Corey Huinker <[email protected]> Date: Sat, 17 Jan 2026 19:06:05 -0500 Subject: [PATCH v10 2/3] Add remote statistics fetching to postgres_fdw. This adds the ability to fetch and import statistics from a remote server table table rather than fetching the data or data sample from that table. This is managed via a new option, fetch_stats, which is available at the server level and table level. The global default is true, but this can be overriden by at the server level, which in turn can be overridden at the table level. If fetch_stats is true, and the remote table is an actual table or materialized view that can hold statistics, and the local table does not have any extended statistics objects built upon it, then the remote database will first be queried for relation statistics and attribute statistics similar to the method used in pg_dump. If there are remote statistics for all of the columns in the local table, then those statistics will be imported using pg_restore_relation_statistics and pg_restore_attribute_statistics functions similar to the way pg_restore uses them. If fetch_stats is false, or if the fetched statistics were missing or otherwise inadequate, then the ANALYZE operation will issue a WARNING and then fall back to regular table sampling to generate local statistics. --- doc/src/sgml/postgres-fdw.sgml | 21 +- .../postgres_fdw/expected/postgres_fdw.out | 15 +- contrib/postgres_fdw/option.c | 5 + contrib/postgres_fdw/postgres_fdw.c | 912 ++++++++++++++++++ contrib/postgres_fdw/sql/postgres_fdw.sql | 13 +- 5 files changed, 963 insertions(+), 3 deletions(-) diff --git a/doc/src/sgml/postgres-fdw.sgml b/doc/src/sgml/postgres-fdw.sgml index 9b032fbf675..933b90de1d0 100644 --- a/doc/src/sgml/postgres-fdw.sgml +++ b/doc/src/sgml/postgres-fdw.sgml @@ -332,7 +332,7 @@ OPTIONS (ADD password_required 'false'); </para> <para> - The following option controls how such an <command>ANALYZE</command> + The following options control how such an <command>ANALYZE</command> operation behaves: </para> @@ -364,6 +364,25 @@ OPTIONS (ADD password_required 'false'); </listitem> </varlistentry> + <varlistentry> + <term><literal>fetch_stats</literal> (<type>boolean</type>)</term> + <listitem> + <para> + This option, which can be specified for a foreign table or a foreign + server, determines if <command>ANALYZE</command> on a foreign table + will instead attempt to fetch the existing relation and attribute + statistics from the remote table, and if all of the attributes being + analyzed have statistics in the remote table, then it will import + those statistics directly using + <function>pg_restore_relation_stats</relation> and + <function>pg_restore_attribute_stats</relation>. This option is only + useful if the remote relation is one that can have regular statistics + (tables and materialized views). + The default is <literal>true</literal>. + </para> + </listitem> + </varlistentry> + </variablelist> </sect3> diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out index 6066510c7c0..cb84d453f4f 100644 --- a/contrib/postgres_fdw/expected/postgres_fdw.out +++ b/contrib/postgres_fdw/expected/postgres_fdw.out @@ -252,6 +252,7 @@ SELECT c3, c4 FROM ft1 ORDER BY c3, c1 LIMIT 1; -- should work again -- Now we should be able to run ANALYZE. -- To exercise multiple code paths, we use local stats on ft1 -- and remote-estimate mode on ft2. +ALTER SERVER loopback OPTIONS (ADD fetch_stats 'false'); ANALYZE ft1; ALTER FOREIGN TABLE ft2 OPTIONS (use_remote_estimate 'true'); -- =================================================================== @@ -4551,7 +4552,8 @@ REINDEX TABLE reind_fdw_parent; -- ok REINDEX TABLE CONCURRENTLY reind_fdw_parent; -- ok DROP TABLE reind_fdw_parent; -- =================================================================== --- conversion error +-- conversion error, will generate a WARNING for imported stats and an +-- error on locally computed stats. -- =================================================================== ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE int; SELECT * FROM ft1 ftx(x1,x2,x3,x4,x5,x6,x7,x8) WHERE x1 = 1; -- ERROR @@ -11462,6 +11464,12 @@ CREATE FOREIGN TABLE async_p2 PARTITION OF async_pt FOR VALUES FROM (2000) TO (3 SERVER loopback2 OPTIONS (table_name 'base_tbl2'); INSERT INTO async_p1 SELECT 1000 + i, i, to_char(i, 'FM0000') FROM generate_series(0, 999, 5) i; INSERT INTO async_p2 SELECT 2000 + i, i, to_char(i, 'FM0000') FROM generate_series(0, 999, 5) i; +-- Will failover to sampling on async_p2 because fetch_stats = true (the default) on +-- loopback2, and is set to false on loopback +ANALYZE async_pt; +WARNING: Failed to import statistics from remote table public.base_tbl2, will try to ANALYZE with regular row sampling. +-- Turning off fetch_stats at the table level for async_p2 removes the warning. +ALTER FOREIGN TABLE async_p2 OPTIONS (ADD fetch_stats 'false'); ANALYZE async_pt; -- simple queries CREATE TABLE result_tbl (a int, b int, c text); @@ -11568,6 +11576,11 @@ CREATE TABLE base_tbl3 (a int, b int, c text); CREATE FOREIGN TABLE async_p3 PARTITION OF async_pt FOR VALUES FROM (3000) TO (4000) SERVER loopback2 OPTIONS (table_name 'base_tbl3'); INSERT INTO async_p3 SELECT 3000 + i, i, to_char(i, 'FM0000') FROM generate_series(0, 999, 5) i; +-- Will fail because fetch_stats = true (the default) on async_p3/loopback2 +ANALYZE async_pt; +WARNING: Failed to import statistics from remote table public.base_tbl3, will try to ANALYZE with regular row sampling. +-- Turn off fetch_stats at the server level. +ALTER SERVER loopback2 OPTIONS (ADD fetch_stats 'false'); ANALYZE async_pt; EXPLAIN (VERBOSE, COSTS OFF) INSERT INTO result_tbl SELECT * FROM async_pt WHERE b === 505; diff --git a/contrib/postgres_fdw/option.c b/contrib/postgres_fdw/option.c index b0bd72d1e58..5b7726800d0 100644 --- a/contrib/postgres_fdw/option.c +++ b/contrib/postgres_fdw/option.c @@ -120,6 +120,7 @@ postgres_fdw_validator(PG_FUNCTION_ARGS) strcmp(def->defname, "async_capable") == 0 || strcmp(def->defname, "parallel_commit") == 0 || strcmp(def->defname, "parallel_abort") == 0 || + strcmp(def->defname, "fetch_stats") == 0 || strcmp(def->defname, "keep_connections") == 0) { /* these accept only boolean values */ @@ -278,6 +279,10 @@ InitPgFdwOptions(void) {"use_scram_passthrough", ForeignServerRelationId, false}, {"use_scram_passthrough", UserMappingRelationId, false}, + /* fetch_stats is available on both server and table */ + {"fetch_stats", ForeignServerRelationId, false}, + {"fetch_stats", ForeignTableRelationId, false}, + /* * sslcert and sslkey are in fact libpq options, but we repeat them * here to allow them to appear in both foreign server context (when diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c index 3572689e33b..86bdfc57c07 100644 --- a/contrib/postgres_fdw/postgres_fdw.c +++ b/contrib/postgres_fdw/postgres_fdw.c @@ -18,10 +18,13 @@ #include "access/sysattr.h" #include "access/table.h" #include "catalog/pg_opfamily.h" +#include "catalog/pg_statistic_ext.h" #include "commands/defrem.h" #include "commands/explain_format.h" #include "commands/explain_state.h" #include "executor/execAsync.h" +#include "executor/spi.h" +#include "fmgr.h" #include "foreign/fdwapi.h" #include "funcapi.h" #include "miscadmin.h" @@ -42,12 +45,14 @@ #include "storage/latch.h" #include "utils/builtins.h" #include "utils/float.h" +#include "utils/fmgroids.h" #include "utils/guc.h" #include "utils/lsyscache.h" #include "utils/memutils.h" #include "utils/rel.h" #include "utils/sampling.h" #include "utils/selfuncs.h" +#include "utils/syscache.h" PG_MODULE_MAGIC_EXT( .name = "postgres_fdw", @@ -317,6 +322,20 @@ typedef struct List *already_used; /* expressions already dealt with */ } ec_member_foreign_arg; +/* Result sets that are returned from a foreign statistics scan */ +typedef struct +{ + PGresult *rel; + PGresult *att; +} RemoteStatsResults; + +/* Pairs of remote columns with local attnums */ +typedef struct +{ + char remote_attname[NAMEDATALEN]; + AttrNumber local_attnum; +} RemoteAttributeMapping; + /* * SQL functions */ @@ -402,6 +421,10 @@ static void postgresExecForeignTruncate(List *rels, static bool postgresAnalyzeForeignTable(Relation relation, AcquireSampleRowsFunc *func, BlockNumber *totalpages); +static bool postgresStatisticsAreImportable(Relation relation); +static bool postgresImportStatistics(Relation relation, + List *va_cols, + int elevel); static List *postgresImportForeignSchema(ImportForeignSchemaStmt *stmt, Oid serverOid); static void postgresGetForeignJoinPaths(PlannerInfo *root, @@ -546,6 +569,188 @@ static void merge_fdw_options(PgFdwRelationInfo *fpinfo, const PgFdwRelationInfo *fpinfo_i); static int get_batch_size_option(Relation rel); +/* + * Static queries for querying remote statistics. + */ + +/* All static relstats queries have the same column order */ +enum RelStatsColumns +{ + RELSTATS_RELKIND = 0, + RELSTATS_RELPAGES, + RELSTATS_RELTUPLES, + RELSTATS_NUM_FIELDS, +}; + +/* range stats introduced in v17 */ +static const char *attstats_query_17 = +"SELECT DISTINCT ON (s.attname COLLATE \"C\") attname, s.null_frac, s.avg_width, " +"s.n_distinct, s.most_common_vals, s.most_common_freqs, " +"s.histogram_bounds, s.correlation, s.most_common_elems, " +"s.most_common_elem_freqs, s.elem_count_histogram, " +"s.range_length_histogram, s.range_empty_frac, s.range_bounds_histogram " +"FROM pg_catalog.pg_stats AS s " +"WHERE s.schemaname = $1 AND s.tablename = $2 " +"AND s.attname = ANY($3::text[]) " +"ORDER BY s.attname COLLATE \"C\", s.inherited DESC"; + +/* elements stats introduced in 9.2 */ +static const char *attstats_query_9_2 = +"SELECT DISTINCT ON (s.attname COLLATE \"C\") attname, s.null_frac, s.avg_width, " +"s.n_distinct, s.most_common_vals, s.most_common_freqs, " +"s.histogram_bounds, s.correlation, s.most_common_elems, " +"s.most_common_elem_freqs, s.elem_count_histogram, " +"NULL AS range_length_histogram, NULL AS range_empty_frac, " +"NULL AS range_bounds_histogram " +"FROM pg_catalog.pg_stats AS s " +"WHERE s.schemaname = $1 AND s.tablename = $2 " +"AND s.attname = ANY($3::text[]) " +"ORDER BY s.attname COLLATE \"C\", s.inherited DESC"; + +/* inherited introduced in 9.0 */ +static const char *attstats_query_9_0 = +"SELECT DISTINCT ON (s.attname COLLATE \"C\") attname, s.null_frac, s.avg_width, " +"s.n_distinct, s.most_common_vals, s.most_common_freqs, " +"s.histogram_bounds, s.correlation, NULL AS most_common_elems, " +"NULL AS most_common_elem_freqs, NULL AS elem_count_histogram, " +"NULL AS range_length_histogram, NULL AS range_empty_frac, " +"NULL AS range_bounds_histogram " +"FROM pg_catalog.pg_stats AS s " +"WHERE s.schemaname = $1 AND s.tablename = $2 " +"AND s.attname = ANY($3::text[]) " +"ORDER BY s.attname COLLATE \"C\", s.inherited DESC"; + +static const char *attstats_query_default = +"SELECT s.attname, s.null_frac, s.avg_width, " +"s.n_distinct, s.most_common_vals, s.most_common_freqs, " +"s.histogram_bounds, s.correlation, NULL AS most_common_elems, " +"NULL AS most_common_elem_freqs, NULL AS elem_count_histogram, " +"NULL AS range_length_histogram, NULL AS range_empty_frac, " +"NULL AS range_bounds_histogram " +"FROM pg_catalog.pg_stats AS s " +"WHERE s.schemaname = $1 AND s.tablename = $2 " +"AND s.attname = ANY($3::text[]) " +"ORDER BY s.attname COLLATE \"C\""; + +/* All static attstats queries have the same column order */ +enum AttStatsColumns +{ + ATTSTATS_ATTNAME = 0, + ATTSTATS_NULL_FRAC, + ATTSTATS_AVG_WIDTH, + ATTSTATS_N_DISTINCT, + ATTSTATS_MOST_COMMON_VALS, + ATTSTATS_MOST_COMMON_FREQS, + ATTSTATS_HISTOGRAM_BOUNDS, + ATTSTATS_CORRELATION, + ATTSTATS_MOST_COMMON_ELEMS, + ATTSTATS_MOST_COMMON_ELEM_FREQS, + ATTSTATS_ELEM_COUNT_HISTOGRAM, + ATTSTATS_RANGE_LENGTH_HISTOGRAM, + ATTSTATS_RANGE_EMPTY_FRAC, + ATTSTATS_RANGE_BOUNDS_HISTOGRAM, + ATTSTATS_NUM_FIELDS, +}; + +static const char *relimport_sql = +"SELECT pg_catalog.pg_restore_relation_stats(\n" +"\t'version', $1,\n" +"\t'schemaname', $2,\n" +"\t'relname', $3,\n" +"\t'relpages', $4::integer,\n" +"\t'reltuples', $5::real)"; + +enum RelImportSqlArgs +{ + RELIMPORT_SQL_VERSION = 0, + RELIMPORT_SQL_SCHEMANAME, + RELIMPORT_SQL_RELNAME, + RELIMPORT_SQL_RELPAGES, + RELIMPORT_SQL_RELTUPLES, + RELIMPORT_SQL_NUM_FIELDS +}; + +static const Oid relimport_argtypes[RELIMPORT_SQL_NUM_FIELDS] = { +INT4OID, TEXTOID, TEXTOID, TEXTOID, TEXTOID,}; + +static const char *attimport_sql = +"SELECT pg_catalog.pg_restore_attribute_stats(\n" +"\t'version', $1,\n" +"\t'schemaname', $2,\n" +"\t'relname', $3,\n" +"\t'attnum', $4,\n" +"\t'inherited', false::boolean,\n" +"\t'null_frac', $5::real,\n" +"\t'avg_width', $6::integer,\n" +"\t'n_distinct', $7::real,\n" +"\t'most_common_vals', $8,\n" +"\t'most_common_freqs', $9::real[],\n" +"\t'histogram_bounds', $10,\n" +"\t'correlation', $11::real,\n" +"\t'most_common_elems', $12,\n" +"\t'most_common_elem_freqs', $13::real[],\n" +"\t'elem_count_histogram', $14::real[],\n" +"\t'range_length_histogram', $15,\n" +"\t'range_empty_frac', $16::real,\n" +"\t'range_bounds_histogram', $17)"; + +enum AttImportSqlArgs +{ + ATTIMPORT_SQL_VERSION = 0, + ATTIMPORT_SQL_SCHEMANAME, + ATTIMPORT_SQL_RELNAME, + ATTIMPORT_SQL_ATTNUM, + ATTIMPORT_SQL_NULL_FRAC, + ATTIMPORT_SQL_AVG_WIDTH, + ATTIMPORT_SQL_N_DISTINCT, + ATTIMPORT_SQL_MOST_COMMON_VALS, + ATTIMPORT_SQL_MOST_COMMON_FREQS, + ATTIMPORT_SQL_HISTOGRAM_BOUNDS, + ATTIMPORT_SQL_CORRELATION, + ATTIMPORT_SQL_MOST_COMMON_ELEMS, + ATTIMPORT_SQL_MOST_COMMON_ELEM_FREQS, + ATTIMPORT_SQL_ELEM_COUNT_HISTOGRAM, + ATTIMPORT_SQL_RANGE_LENGTH_HISTOGRAM, + ATTIMPORT_SQL_RANGE_EMPTY_FRAC, + ATTIMPORT_SQL_RANGE_BOUNDS_HISTOGRAM, + ATTIMPORT_SQL_NUM_FIELDS +}; + +static const Oid attimport_argtypes[ATTIMPORT_SQL_NUM_FIELDS] = { + INT4OID, TEXTOID, TEXTOID, INT2OID, + TEXTOID, TEXTOID, TEXTOID, TEXTOID, + TEXTOID, TEXTOID, TEXTOID, TEXTOID, + TEXTOID, TEXTOID, TEXTOID, TEXTOID, +TEXTOID,}; + +/* Pairs AttStatsColumns:AttImportSqlArgs Map */ +typedef struct +{ + enum AttStatsColumns res_field; + enum AttImportSqlArgs arg_num; +} AttrResultArgMap; + +/* + * The mapping of attribute stats query columns to the positional arguments in + * the prepared pg_restore_attribute_stats() statement. + */ +#define NUM_MAPPED_ATTIMPORT_ARGS 13 +static const AttrResultArgMap attr_result_arg_map[NUM_MAPPED_ATTIMPORT_ARGS] = { + {ATTSTATS_NULL_FRAC, ATTIMPORT_SQL_NULL_FRAC}, + {ATTSTATS_AVG_WIDTH, ATTIMPORT_SQL_AVG_WIDTH}, + {ATTSTATS_N_DISTINCT, ATTIMPORT_SQL_N_DISTINCT}, + {ATTSTATS_MOST_COMMON_VALS, ATTIMPORT_SQL_MOST_COMMON_VALS}, + {ATTSTATS_MOST_COMMON_FREQS, ATTIMPORT_SQL_MOST_COMMON_FREQS}, + {ATTSTATS_HISTOGRAM_BOUNDS, ATTIMPORT_SQL_HISTOGRAM_BOUNDS}, + {ATTSTATS_CORRELATION, ATTIMPORT_SQL_CORRELATION}, + {ATTSTATS_MOST_COMMON_ELEMS, ATTIMPORT_SQL_MOST_COMMON_ELEMS}, + {ATTSTATS_MOST_COMMON_ELEM_FREQS, ATTIMPORT_SQL_MOST_COMMON_ELEM_FREQS}, + {ATTSTATS_ELEM_COUNT_HISTOGRAM, ATTIMPORT_SQL_ELEM_COUNT_HISTOGRAM}, + {ATTSTATS_RANGE_LENGTH_HISTOGRAM, ATTIMPORT_SQL_RANGE_LENGTH_HISTOGRAM}, + {ATTSTATS_RANGE_EMPTY_FRAC, ATTIMPORT_SQL_RANGE_EMPTY_FRAC}, + {ATTSTATS_RANGE_BOUNDS_HISTOGRAM, ATTIMPORT_SQL_RANGE_BOUNDS_HISTOGRAM}, +}; + /* * Foreign-data wrapper handler function: return a struct with pointers @@ -595,6 +800,8 @@ postgres_fdw_handler(PG_FUNCTION_ARGS) /* Support functions for ANALYZE */ routine->AnalyzeForeignTable = postgresAnalyzeForeignTable; + routine->StatisticsAreImportable = postgresStatisticsAreImportable; + routine->ImportStatistics = postgresImportStatistics; /* Support functions for IMPORT FOREIGN SCHEMA */ routine->ImportForeignSchema = postgresImportForeignSchema; @@ -4935,6 +5142,711 @@ postgresAnalyzeForeignTable(Relation relation, return true; } +/* + * Test if an attribute name is in the list. + * + * An empty list means that all attribute names are in the list. + */ +static bool +attname_in_list(const char *attname, List *va_cols) +{ + ListCell *le; + + if (va_cols == NIL) + return true; + + foreach(le, va_cols) + { + char *col = strVal(lfirst(le)); + + if (strcmp(attname, col) == 0) + return true; + } + return false; +} + +/* + * Move a string value from a result set to a Text value of a Datum array. + */ +static void +map_field_to_arg(PGresult *res, int row, int field, + int arg, Datum *values, char *nulls) +{ + if (PQgetisnull(res, row, field)) + { + values[arg] = (Datum) 0; + nulls[arg] = 'n'; + } + else + { + const char *s = PQgetvalue(res, row, field); + + values[arg] = CStringGetTextDatum(s); + nulls[arg] = ' '; + } +} + +/* + * Check the 1x1 result set of a pg_restore_*_stats() command for success. + */ +static bool +import_spi_query_ok(int spirc) +{ + char *s; + bool ok; + + if (spirc != SPI_OK_SELECT + || SPI_tuptable == NULL + || SPI_processed != 1) + return false; + + s = SPI_getvalue(SPI_tuptable->vals[0], SPI_tuptable->tupdesc, 1); + + ok = (s != NULL && s[0] == 't' && s[1] == '\0'); + pfree(s); + + return ok; +} + +/* + * Import fetched statistics into the local statistics tables. + */ +static bool +import_fetched_statistics(const char *schemaname, const char *relname, + int server_version_num, int natts, + const RemoteAttributeMapping * remattrmap, + RemoteStatsResults * remstats) +{ + SPIPlanPtr plan = NULL; + PGresult *res = remstats->att; + int spirc; + int mapidx = 0; + Datum values[ATTIMPORT_SQL_NUM_FIELDS]; + char nulls[ATTIMPORT_SQL_NUM_FIELDS]; + bool ok = false; + + /* Assign all the invariant parameters */ + values[ATTIMPORT_SQL_VERSION] = Int32GetDatum(server_version_num); + nulls[ATTIMPORT_SQL_VERSION] = ' '; + + values[ATTIMPORT_SQL_SCHEMANAME] = CStringGetTextDatum(schemaname); + nulls[ATTIMPORT_SQL_SCHEMANAME] = ' '; + + values[ATTIMPORT_SQL_RELNAME] = CStringGetTextDatum(relname); + nulls[ATTIMPORT_SQL_RELNAME] = ' '; + + nulls[ATTIMPORT_SQL_ATTNUM] = ' '; + + SPI_connect(); + + plan = SPI_prepare(attimport_sql, ATTIMPORT_SQL_NUM_FIELDS, + (Oid *) attimport_argtypes); + + if (plan == NULL || SPI_result < 0) + { + ereport(WARNING, + errmsg("Import attribute statistics prepare failed %s " + "with error code %d", + attimport_sql, SPI_result)); + goto import_cleanup; + } + + /* + * Match result set rows to local attnums. + * + * Every row of the result should be an attribute that we specifically + * filtered for, so every row should have at least one match in the + * RemoteAttributeMapping, which is also ordered by attname, so we only + * need to walk that array once. + * + * We import the attribute statistics first, because those are more prone + * to errors. This avoids making a modification of pg_class that will just + * get rolled back by a failed attribute import. + */ + for (int row = 0; row < PQntuples(remstats->att); row++) + { + char *remote_attname; + bool match_found = false; + int cmp = 0; + + if (PQgetisnull(res, row, ATTSTATS_ATTNAME)) + { + ereport(WARNING, + errmsg("Remote statistics returned a row with NULL attribute name")); + goto import_cleanup; + } + + remote_attname = PQgetvalue(res, row, ATTSTATS_ATTNAME); + + /* + * Handle a series of matching elements in the mapping. + * + * We exit this loop in the following ways: + * + * 1. Having found at least match and exhausting the list. We're done. + * 2. Having found at least match and ending on a <, advance. 3. + * Having found at least match and ending on a >, bad sort. 4. No + * match, list exhausted. 5. No match, <. 6. No match, >. + * + */ + for (; mapidx < natts; mapidx++) + { + cmp = strcmp(remote_attname, remattrmap[mapidx].remote_attname); + + /* Stop scanning on the first non-match */ + if (cmp != 0) + break; + + match_found = true; + values[ATTIMPORT_SQL_ATTNUM] = + Int16GetDatum(remattrmap[mapidx].local_attnum); + + /* Loop through all mappable columns->arguments */ + for (int i = 0; i < NUM_MAPPED_ATTIMPORT_ARGS; i++) + map_field_to_arg(res, row, + attr_result_arg_map[i].res_field, + attr_result_arg_map[i].arg_num, + values, nulls); + + spirc = SPI_execute_plan(plan, values, nulls, false, 0); + + if (!import_spi_query_ok(spirc)) + { + ereport(WARNING, + errmsg("Attribute statistics import failed %s", + attimport_sql)); + goto import_cleanup; + } + } + + /* We found a match, move onto the next result. */ + if (match_found) + continue; + + /* + * If no match and we ended on a <, then the mapidx will never find a + * match, so stop now and let the cleanup report the error. + */ + if (cmp > 0) + break; + + /* + * Otherwise this result found no matching mapidx, which should only + * happen if the results are out of sort or the wrong query was + * executed. + */ + if (cmp < 0) + { + ereport(WARNING, + errmsg("No remote statistics found for %s of %s.", + quote_identifier(remattrmap[mapidx].remote_attname), + quote_qualified_identifier(schemaname, relname))); + goto import_cleanup; + } + } + + /* Look for a mapidx with no possible matching result */ + if (mapidx < natts) + { + ereport(WARNING, + errmsg("No remote statistics found for %s of %s.", + quote_identifier(remattrmap[mapidx].remote_attname), + quote_qualified_identifier(schemaname, relname))); + goto import_cleanup; + } + + /* + * Import relstats. + * + * Import relation stats. We only perform this once, so there is no point + * in preparing the statement. + * + * We can re-use the values/nulls because the number of parameters is less + * and the first three params are the same as attstats_import. + */ + map_field_to_arg(remstats->rel, 0, RELSTATS_RELPAGES, + RELIMPORT_SQL_RELPAGES, values, nulls); + map_field_to_arg(remstats->rel, 0, RELSTATS_RELTUPLES, + RELIMPORT_SQL_RELTUPLES, values, nulls); + + spirc = SPI_execute_with_args(relimport_sql, RELIMPORT_SQL_NUM_FIELDS, + (Oid *) relimport_argtypes, + values, nulls, false, 1); + + if (!import_spi_query_ok(spirc)) + { + ereport(WARNING, + errmsg("Relation statistics import failed %s", + relimport_sql)); + goto import_cleanup; + } + + ok = true; + +import_cleanup: + if (plan) + SPI_freeplan(plan); + SPI_finish(); + return ok; +} + +/* + * Attempt to fetch remote relations stats. + * + * Verify that the result is of the proper shape, return NULL otherwise. + */ +static PGresult * +fetch_relstats(PGconn *conn, + const char *remote_schemaname, const char *remote_relname) +{ + const char *params[2] = {remote_schemaname, remote_relname}; + + /* + * Before v14, a reltuples value of 0 was ambiguous: it could either mean + * the relation is empty, or it could mean that it hadn't yet been + * vacuumed or analyzed. (Newer versions use -1 for the latter case). + * + * We can ignore this change, because if the remote table wasn't analyzed, + * then it would have no attribute stats, and thus we wouldn't have stats + * that we would try to import. So we can take the reltuples value as-is. + */ + const char *sql = "SELECT c.relkind, c.relpages, c.reltuples " + "FROM pg_catalog.pg_class AS c " + "JOIN pg_catalog.pg_namespace AS n " + "ON n.oid = c.relnamespace " + "WHERE n.nspname = $1 AND c.relname = $2"; + + PGresult *res = NULL; + + if (!PQsendQueryParams(conn, sql, 2, NULL, params, NULL, NULL, 0)) + { + pgfdw_report(WARNING, NULL, conn, sql); + return NULL; + } + + res = pgfdw_get_result(conn); + + if (res == NULL + || PQresultStatus(res) != PGRES_TUPLES_OK + || PQntuples(res) != 1 + || PQnfields(res) != RELSTATS_NUM_FIELDS + || PQgetisnull(res, 0, RELSTATS_RELKIND)) + { + pgfdw_report(WARNING, res, conn, sql); + PQclear(res); + return NULL; + } + + return res; +} + +/* + * Attempt to fetch remote attribute stats. + * + * Verify that the result is of the proper shape, return NULL otherwise. Note + * that we do not verify the row count. + */ +static PGresult * +fetch_attstats(PGconn *conn, + const char *remote_schemaname, const char *remote_relname, + const char *column_list) +{ + const char *params[3] = {remote_schemaname, remote_relname, column_list}; + int version = PQserverVersion(conn); + const char *sql; + PGresult *res; + + if (version >= 170000) + sql = attstats_query_17; + else if (version >= 90200) + sql = attstats_query_9_2; + else if (version >= 90000) + sql = attstats_query_9_0; + else + sql = attstats_query_default; + + if (!PQsendQueryParams(conn, sql, 3, NULL, params, NULL, NULL, 0)) + { + pgfdw_report(WARNING, NULL, conn, sql); + return NULL; + } + + res = pgfdw_get_result(conn); + + if (res == NULL + || PQresultStatus(res) != PGRES_TUPLES_OK + || PQnfields(res) != ATTSTATS_NUM_FIELDS) + { + pgfdw_report(WARNING, res, conn, sql); + PQclear(res); + return NULL; + } + + return res; +} + +/* + * Make a '{column,list,array}'. + */ +static char * +get_column_list(int natts, const RemoteAttributeMapping * remattrmap) +{ + StringInfoData column_list; + + initStringInfo(&column_list); + appendStringInfoChar(&column_list, '{'); + for (int i = 0; i < natts; i++) + { + if (i > 0) + appendStringInfoChar(&column_list, ','); + appendStringInfoString(&column_list, + quote_identifier(remattrmap[i].remote_attname)); + } + appendStringInfoChar(&column_list, '}'); + + return column_list.data; +} + +/* + * Attempt to fetch statistics from a remote server. + */ +static bool +fetch_remote_statistics(PGconn *conn, + const char *remote_schemaname, + const char *remote_relname, + int server_version_num, int natts, + const RemoteAttributeMapping * remattrmap, + RemoteStatsResults * remstats) +{ + char *column_list = NULL; + PGresult *attstats = NULL; + PGresult *relstats = NULL; + + char relkind; + + relstats = fetch_relstats(conn, remote_schemaname, remote_relname); + + if (relstats == NULL) + goto fetch_remote_statistics_fail; + + /* + * Verify that the remote table is the sort that can have meaningful stats + * in pg_stats. + * + * Note that while relations of kinds RELKIND_INDEX and + * RELKIND_PARTITIONED_INDEX can have rows in pg_stats, they obviously + * can't support a foreign table. + */ + relkind = *PQgetvalue(relstats, 0, RELSTATS_RELKIND); + + switch (relkind) + { + case RELKIND_RELATION: + case RELKIND_PARTITIONED_TABLE: + case RELKIND_FOREIGN_TABLE: + case RELKIND_MATVIEW: + break; + default: + goto fetch_remote_statistics_fail; + } + + column_list = get_column_list(natts, remattrmap); + + /* See if it actually has any attribute stats. */ + attstats = fetch_attstats(conn, remote_schemaname, remote_relname, + column_list); + + /* + * If we got attribute statistics results, then we are done with fetching. + */ + if (attstats != NULL + && PQntuples(attstats) > 0) + { + pfree(column_list); + remstats->rel = relstats; + remstats->att = attstats; + return true; + } + +fetch_remote_statistics_fail: + ereport(WARNING, + errmsg("Failed to import statistics from remote table %s, " + "will try to ANALYZE with regular row sampling.", + quote_qualified_identifier(remote_schemaname, + remote_relname))); + PQclear(attstats); + PQclear(relstats); + if (column_list) + pfree(column_list); + return false; +} + +/* + * Test if the relation has extended statistics objects. + */ +static bool +table_has_extended_stats(Relation relation) +{ + Relation pg_statext; + SysScanDesc scan; + ScanKeyData skey; + bool found; + + pg_statext = table_open(StatisticExtRelationId, RowExclusiveLock); + + /* + * Prepare to scan pg_statistic_ext for entries having stxrelid = this + * rel. + */ + ScanKeyInit(&skey, + Anum_pg_statistic_ext_stxrelid, + BTEqualStrategyNumber, F_OIDEQ, + ObjectIdGetDatum(RelationGetRelid(relation))); + + scan = systable_beginscan(pg_statext, StatisticExtRelidIndexId, true, + NULL, 1, &skey); + + found = (systable_getnext(scan) != NULL); + + systable_endscan(scan); + + table_close(pg_statext, RowExclusiveLock); + + return found; +} + +static bool +postgresStatisticsAreImportable(Relation relation) +{ + ForeignTable *table; + ForeignServer *server; + ListCell *lc; + bool fetch_stats = true; + + table = GetForeignTable(RelationGetRelid(relation)); + server = GetForeignServer(table->serverid); + + /* + * Server-level options can be overridden by table-level options, so check + * server-level first. + */ + foreach(lc, server->options) + { + DefElem *def = (DefElem *) lfirst(lc); + + if (strcmp(def->defname, "fetch_stats") == 0) + { + fetch_stats = defGetBoolean(def); + break; + } + } + + foreach(lc, table->options) + { + DefElem *def = (DefElem *) lfirst(lc); + + if (strcmp(def->defname, "fetch_stats") == 0) + { + fetch_stats = defGetBoolean(def); + break; + } + } + + /* + * Additional checks that can disqualify a table from importing stats. + */ + if (fetch_stats) + { + /* + * We can't compute extended stats from the column stats, for that we + * need a table sample. + */ + if (table_has_extended_stats(relation)) + { + ereport(ERROR, + errcode(ERRCODE_FEATURE_NOT_SUPPORTED), + errmsg("Cannot import statistics for foreign table \"%s\" " + "because it has extended statistics objects.", + RelationGetRelationName(relation))); + fetch_stats = false; + } + } + + return fetch_stats; +} + +/* + * Compare two RemoteAttributeMappings for sorting. + */ +static int +remattrmap_cmp(const void *v1, const void *v2) +{ + const RemoteAttributeMapping *r1 = v1; + const RemoteAttributeMapping *r2 = v2; + + return strncmp(r1->remote_attname, r2->remote_attname, NAMEDATALEN); +} + +/* + * Fetch attstattarget from a pg_attribute tuple. + */ +static int16 +get_attstattarget(Relation relation, AttrNumber attnum) +{ + HeapTuple atttuple; + bool isnull; + Datum dat; + int16 attstattarget; + Oid relid = RelationGetRelid(relation); + + atttuple = SearchSysCache2(ATTNUM, + ObjectIdGetDatum(relid), + Int16GetDatum(attnum)); + if (!HeapTupleIsValid(atttuple)) + elog(ERROR, "cache lookup failed for attribute %d of relation %u", + attnum, relid); + dat = SysCacheGetAttr(ATTNUM, atttuple, + Anum_pg_attribute_attstattarget, + &isnull); + attstattarget = isnull ? -1 : DatumGetInt16(dat); + ReleaseSysCache(atttuple); + + return attstattarget; +} + +/* + * postgresImportStatistics + * Attempt to fetch remote statistics and apply those instead of analyzing. + */ +static bool +postgresImportStatistics(Relation relation, List *va_cols, int elevel) +{ + + ForeignTable *table; + UserMapping *user; + PGconn *conn; + ListCell *lc; + int server_version_num = 0; + const char *schemaname = NULL; + const char *relname = NULL; + const char *remote_schemaname = NULL; + const char *remote_relname = NULL; + TupleDesc tupdesc = RelationGetDescr(relation); + int natts = 0; + bool ok = false; + + RemoteAttributeMapping *remattrmap; + + RemoteStatsResults remstats = {.rel = NULL,.att = NULL}; + + table = GetForeignTable(RelationGetRelid(relation)); + user = GetUserMapping(GetUserId(), table->serverid); + conn = GetConnection(user, false, NULL); + server_version_num = PQserverVersion(conn); + schemaname = get_namespace_name(RelationGetNamespace(relation)); + relname = RelationGetRelationName(relation); + + foreach(lc, table->options) + { + DefElem *def = (DefElem *) lfirst(lc); + + if (strcmp(def->defname, "schema_name") == 0) + remote_schemaname = defGetString(def); + else if (strcmp(def->defname, "table_name") == 0) + remote_relname = defGetString(def); + } + + /* + * Assume the relation/schema names are the same as the local name unless + * the options tell us otherwise. + */ + if (remote_schemaname == NULL) + remote_schemaname = schemaname; + if (remote_relname == NULL) + remote_relname = relname; + + /* + * Build attnum/remote-attname list. + * + */ + remattrmap = palloc_array(RemoteAttributeMapping, tupdesc->natts); + for (int i = 0; i < tupdesc->natts; i++) + { + char *attname; + char *remote_colname; + List *fc_options; + ListCell *fc_lc; + AttrNumber attnum; + + Form_pg_attribute attr = TupleDescAttr(tupdesc, i); + + /* Ignore dropped columns. */ + if (attr->attisdropped) + continue; + + /* Ignore generated columns. */ + if (attr->attgenerated) + continue; + + attname = NameStr(attr->attname); + + /* If a list is specified, exclude any attnames not in it. */ + if (!attname_in_list(attname, va_cols)) + continue; + + attnum = attr->attnum; + + /* Ignore if attstatarget is 0 */ + if (get_attstattarget(relation, attnum) == 0) + continue; + + /* If column_name is not specified, go with attname. */ + remote_colname = attname; + fc_options = GetForeignColumnOptions(RelationGetRelid(relation), attnum); + + foreach(fc_lc, fc_options) + { + DefElem *def = (DefElem *) lfirst(fc_lc); + + if (strcmp(def->defname, "column_name") == 0) + { + remote_colname = defGetString(def); + break; + } + } + + remattrmap[natts].local_attnum = attnum; + strncpy(remattrmap[natts].remote_attname, remote_colname, NAMEDATALEN); + natts++; + } + + /* Sort mapping by remote attribute name */ + qsort(remattrmap, natts, sizeof(RemoteAttributeMapping), remattrmap_cmp); + + ok = fetch_remote_statistics(conn, remote_schemaname, remote_relname, + server_version_num, natts, remattrmap, + &remstats); + + ReleaseConnection(conn); + + if (ok) + { + Assert(remstats.rel != NULL); + Assert(PQnfields(remstats.rel) == RELSTATS_NUM_FIELDS); + Assert(PQntuples(remstats.rel) == 1); + Assert(remstats.att != NULL); + Assert(PQnfields(remstats.att) == ATTSTATS_NUM_FIELDS); + Assert(PQntuples(remstats.att) >= 1); + ok = import_fetched_statistics(schemaname, relname, server_version_num, + natts, remattrmap, &remstats); + } + + pfree(remattrmap); + PQclear(remstats.att); + PQclear(remstats.rel); + return ok; +} + /* * postgresGetAnalyzeInfoForForeignTable * Count tuples in foreign table (just get pg_class.reltuples). diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql index 4f7ab2ed0ac..ea4a2153190 100644 --- a/contrib/postgres_fdw/sql/postgres_fdw.sql +++ b/contrib/postgres_fdw/sql/postgres_fdw.sql @@ -241,6 +241,7 @@ SELECT c3, c4 FROM ft1 ORDER BY c3, c1 LIMIT 1; -- should work again -- Now we should be able to run ANALYZE. -- To exercise multiple code paths, we use local stats on ft1 -- and remote-estimate mode on ft2. +ALTER SERVER loopback OPTIONS (ADD fetch_stats 'false'); ANALYZE ft1; ALTER FOREIGN TABLE ft2 OPTIONS (use_remote_estimate 'true'); @@ -1286,7 +1287,8 @@ REINDEX TABLE CONCURRENTLY reind_fdw_parent; -- ok DROP TABLE reind_fdw_parent; -- =================================================================== --- conversion error +-- conversion error, will generate a WARNING for imported stats and an +-- error on locally computed stats. -- =================================================================== ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE int; SELECT * FROM ft1 ftx(x1,x2,x3,x4,x5,x6,x7,x8) WHERE x1 = 1; -- ERROR @@ -3903,6 +3905,11 @@ CREATE FOREIGN TABLE async_p2 PARTITION OF async_pt FOR VALUES FROM (2000) TO (3 SERVER loopback2 OPTIONS (table_name 'base_tbl2'); INSERT INTO async_p1 SELECT 1000 + i, i, to_char(i, 'FM0000') FROM generate_series(0, 999, 5) i; INSERT INTO async_p2 SELECT 2000 + i, i, to_char(i, 'FM0000') FROM generate_series(0, 999, 5) i; +-- Will failover to sampling on async_p2 because fetch_stats = true (the default) on +-- loopback2, and is set to false on loopback +ANALYZE async_pt; +-- Turning off fetch_stats at the table level for async_p2 removes the warning. +ALTER FOREIGN TABLE async_p2 OPTIONS (ADD fetch_stats 'false'); ANALYZE async_pt; -- simple queries @@ -3940,6 +3947,10 @@ CREATE TABLE base_tbl3 (a int, b int, c text); CREATE FOREIGN TABLE async_p3 PARTITION OF async_pt FOR VALUES FROM (3000) TO (4000) SERVER loopback2 OPTIONS (table_name 'base_tbl3'); INSERT INTO async_p3 SELECT 3000 + i, i, to_char(i, 'FM0000') FROM generate_series(0, 999, 5) i; +-- Will fail because fetch_stats = true (the default) on async_p3/loopback2 +ANALYZE async_pt; +-- Turn off fetch_stats at the server level. +ALTER SERVER loopback2 OPTIONS (ADD fetch_stats 'false'); ANALYZE async_pt; EXPLAIN (VERBOSE, COSTS OFF) -- 2.52.0
From 8b4ffd7f187febc05094accc8e2bba71d7d49a0d Mon Sep 17 00:00:00 2001 From: Corey Huinker <[email protected]> Date: Sat, 17 Jan 2026 19:33:53 -0500 Subject: [PATCH v10 3/3] Add remote_analyze to postgres_fdw remote statistics fetching. This is accomplished through a new option, remote_analyze, which is available at the server level and table level. The default value is false. If remote_analyze is enabled, and if the first attempt to fetch remote statistics did not fetch attribute statistics for every local table column, then an attempt will be made to ANALYZE the remote table. If that remote ANALYZE succeeds, then a second and final attempt will be made to fetch remote statistics. If the statistics found are still insufficient, then the local ANALYZE command will fall back to regular row sampling and computing the statistics locally. --- doc/src/sgml/postgres-fdw.sgml | 16 ++++ .../postgres_fdw/expected/postgres_fdw.out | 38 +++++++++ contrib/postgres_fdw/option.c | 5 ++ contrib/postgres_fdw/postgres_fdw.c | 80 ++++++++++++++++++- contrib/postgres_fdw/sql/postgres_fdw.sql | 34 ++++++++ 5 files changed, 171 insertions(+), 2 deletions(-) diff --git a/doc/src/sgml/postgres-fdw.sgml b/doc/src/sgml/postgres-fdw.sgml index 933b90de1d0..5d46f619a7c 100644 --- a/doc/src/sgml/postgres-fdw.sgml +++ b/doc/src/sgml/postgres-fdw.sgml @@ -383,6 +383,22 @@ OPTIONS (ADD password_required 'false'); </listitem> </varlistentry> + <varlistentry> + <term><literal>remote_analyze</literal> (<type>boolean</type>)</term> + <listitem> + <para> + This option, which can be specified for a foreign table or a foreign + server, determines whether an <command>ANALYZE</command> on a foreign + table will attempt to <command>ANALYZE</command> the remote table if + the first attempt to fetch remote statistics fails, and will then + make a second and final attempt to fetch remote statistics. This option + has no meaning if the foreign table has <literal>fetch_stats</literal> + disabled. + The default is <literal>false</literal>. + </para> + </listitem> + </varlistentry> + </variablelist> </sect3> diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out index cb84d453f4f..b3ec0ce1559 100644 --- a/contrib/postgres_fdw/expected/postgres_fdw.out +++ b/contrib/postgres_fdw/expected/postgres_fdw.out @@ -12678,6 +12678,44 @@ ANALYZE analyze_ftable; DROP FOREIGN TABLE analyze_ftable; DROP TABLE analyze_table; -- =================================================================== +-- test remote analyze +-- =================================================================== +CREATE TABLE remote_analyze_table (id int, a text, b bigint); +INSERT INTO remote_analyze_table (SELECT x FROM generate_series(1,1000) x); +CREATE FOREIGN TABLE remote_analyze_ftable (id int, a text, b bigint) + SERVER loopback + OPTIONS (table_name 'remote_analyze_table', + fetch_stats 'true', + remote_analyze 'true'); +-- no stats before +SELECT s.tablename, COUNT(*) AS num_stats +FROM pg_stats AS s +WHERE s.schemaname = 'public' +AND s.tablename IN ('remote_analyze_table', 'remote_analyze_ftable') +GROUP BY s.tablename +ORDER BY s.tablename; + tablename | num_stats +-----------+----------- +(0 rows) + +ANALYZE remote_analyze_ftable; +-- both stats after +SELECT s.tablename, COUNT(*) AS num_stats +FROM pg_stats AS s +WHERE s.schemaname = 'public' +AND s.tablename IN ('remote_analyze_table', 'remote_analyze_ftable') +GROUP BY s.tablename +ORDER BY s.tablename; + tablename | num_stats +-----------------------+----------- + remote_analyze_ftable | 3 + remote_analyze_table | 3 +(2 rows) + +-- cleanup +DROP FOREIGN TABLE remote_analyze_ftable; +DROP TABLE remote_analyze_table; +-- =================================================================== -- test for postgres_fdw_get_connections function with check_conn = true -- =================================================================== -- Disable debug_discard_caches in order to manage remote connections diff --git a/contrib/postgres_fdw/option.c b/contrib/postgres_fdw/option.c index 5b7726800d0..2941ecbfb87 100644 --- a/contrib/postgres_fdw/option.c +++ b/contrib/postgres_fdw/option.c @@ -121,6 +121,7 @@ postgres_fdw_validator(PG_FUNCTION_ARGS) strcmp(def->defname, "parallel_commit") == 0 || strcmp(def->defname, "parallel_abort") == 0 || strcmp(def->defname, "fetch_stats") == 0 || + strcmp(def->defname, "remote_analyze") == 0 || strcmp(def->defname, "keep_connections") == 0) { /* these accept only boolean values */ @@ -283,6 +284,10 @@ InitPgFdwOptions(void) {"fetch_stats", ForeignServerRelationId, false}, {"fetch_stats", ForeignTableRelationId, false}, + /* remote_analyze is available on both server and table */ + {"remote_analyze", ForeignServerRelationId, false}, + {"remote_analyze", ForeignTableRelationId, false}, + /* * sslcert and sslkey are in fact libpq options, but we repeat them * here to allow them to appear in both foreign server context (when diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c index 86bdfc57c07..1ba743c7fb2 100644 --- a/contrib/postgres_fdw/postgres_fdw.c +++ b/contrib/postgres_fdw/postgres_fdw.c @@ -5390,6 +5390,36 @@ import_cleanup: return ok; } +/* + * Analyze a remote table. + */ +static bool +analyze_remote_table(PGconn *conn, const char *remote_schemaname, + const char *remote_relname) +{ + StringInfoData buf; + PGresult *res; + bool ok = true; + + initStringInfo(&buf); + + appendStringInfo(&buf, "ANALYZE %s", + quote_qualified_identifier(remote_schemaname, remote_relname)); + + res = pgfdw_exec_query(conn, buf.data, NULL); + + if (res == NULL || + PQresultStatus(res) != PGRES_COMMAND_OK) + { + pgfdw_report(WARNING, res, conn, buf.data); + ok = false; + } + + PQclear(res); + pfree(buf.data); + return ok; +} + /* * Attempt to fetch remote relations stats. * @@ -5516,7 +5546,7 @@ fetch_remote_statistics(PGconn *conn, const char *remote_relname, int server_version_num, int natts, const RemoteAttributeMapping * remattrmap, - RemoteStatsResults * remstats) + bool remote_analyze, RemoteStatsResults * remstats) { char *column_list = NULL; PGresult *attstats = NULL; @@ -5568,6 +5598,35 @@ fetch_remote_statistics(PGconn *conn, return true; } + /* + * If remote_analyze is enabled, then we will try to analyze the table and + * then try again. + */ + if (!remote_analyze) + goto fetch_remote_statistics_fail; + + if (!analyze_remote_table(conn, remote_schemaname, remote_relname)) + goto fetch_remote_statistics_fail; + + PQclear(attstats); + attstats = fetch_attstats(conn, remote_schemaname, remote_relname, + column_list); + + if (attstats == NULL || PQntuples(attstats) == 0) + goto fetch_remote_statistics_fail; + + PQclear(relstats); + relstats = fetch_relstats(conn, remote_schemaname, remote_relname); + + if (relstats == NULL) + goto fetch_remote_statistics_fail; + + /* Second attempt worked */ + pfree(column_list); + remstats->rel = relstats; + remstats->att = attstats; + return true; + fetch_remote_statistics_fail: ereport(WARNING, errmsg("Failed to import statistics from remote table %s, " @@ -5723,9 +5782,11 @@ postgresImportStatistics(Relation relation, List *va_cols, int elevel) { ForeignTable *table; + ForeignServer *server; UserMapping *user; PGconn *conn; ListCell *lc; + bool remote_analyze = false; int server_version_num = 0; const char *schemaname = NULL; const char *relname = NULL; @@ -5740,12 +5801,25 @@ postgresImportStatistics(Relation relation, List *va_cols, int elevel) RemoteStatsResults remstats = {.rel = NULL,.att = NULL}; table = GetForeignTable(RelationGetRelid(relation)); + server = GetForeignServer(table->serverid); user = GetUserMapping(GetUserId(), table->serverid); conn = GetConnection(user, false, NULL); server_version_num = PQserverVersion(conn); schemaname = get_namespace_name(RelationGetNamespace(relation)); relname = RelationGetRelationName(relation); + /* + * Server-level options can be overridden by table-level options, so check + * server-level first. + */ + foreach(lc, server->options) + { + DefElem *def = (DefElem *) lfirst(lc); + + if (strcmp(def->defname, "remote_analyze") == 0) + remote_analyze = defGetBoolean(def); + } + foreach(lc, table->options) { DefElem *def = (DefElem *) lfirst(lc); @@ -5754,6 +5828,8 @@ postgresImportStatistics(Relation relation, List *va_cols, int elevel) remote_schemaname = defGetString(def); else if (strcmp(def->defname, "table_name") == 0) remote_relname = defGetString(def); + else if (strcmp(def->defname, "remote_analyze") == 0) + remote_analyze = defGetBoolean(def); } /* @@ -5825,7 +5901,7 @@ postgresImportStatistics(Relation relation, List *va_cols, int elevel) ok = fetch_remote_statistics(conn, remote_schemaname, remote_relname, server_version_num, natts, remattrmap, - &remstats); + remote_analyze, &remstats); ReleaseConnection(conn); diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql index ea4a2153190..ac284fba069 100644 --- a/contrib/postgres_fdw/sql/postgres_fdw.sql +++ b/contrib/postgres_fdw/sql/postgres_fdw.sql @@ -4398,6 +4398,40 @@ ANALYZE analyze_ftable; DROP FOREIGN TABLE analyze_ftable; DROP TABLE analyze_table; +-- =================================================================== +-- test remote analyze +-- =================================================================== +CREATE TABLE remote_analyze_table (id int, a text, b bigint); +INSERT INTO remote_analyze_table (SELECT x FROM generate_series(1,1000) x); + +CREATE FOREIGN TABLE remote_analyze_ftable (id int, a text, b bigint) + SERVER loopback + OPTIONS (table_name 'remote_analyze_table', + fetch_stats 'true', + remote_analyze 'true'); + +-- no stats before +SELECT s.tablename, COUNT(*) AS num_stats +FROM pg_stats AS s +WHERE s.schemaname = 'public' +AND s.tablename IN ('remote_analyze_table', 'remote_analyze_ftable') +GROUP BY s.tablename +ORDER BY s.tablename; + +ANALYZE remote_analyze_ftable; + +-- both stats after +SELECT s.tablename, COUNT(*) AS num_stats +FROM pg_stats AS s +WHERE s.schemaname = 'public' +AND s.tablename IN ('remote_analyze_table', 'remote_analyze_ftable') +GROUP BY s.tablename +ORDER BY s.tablename; + +-- cleanup +DROP FOREIGN TABLE remote_analyze_ftable; +DROP TABLE remote_analyze_table; + -- =================================================================== -- test for postgres_fdw_get_connections function with check_conn = true -- =================================================================== -- 2.52.0
