diff options
| -rw-r--r-- | contrib/postgres_fdw/deparse.c | 7 | ||||
| -rw-r--r-- | contrib/postgres_fdw/postgres_fdw.c | 60 | ||||
| -rw-r--r-- | contrib/postgres_fdw/postgres_fdw.h | 2 |
3 files changed, 47 insertions, 22 deletions
diff --git a/contrib/postgres_fdw/deparse.c b/contrib/postgres_fdw/deparse.c index 4461fb06f02..21237d18ef8 100644 --- a/contrib/postgres_fdw/deparse.c +++ b/contrib/postgres_fdw/deparse.c @@ -2368,14 +2368,15 @@ deparseAnalyzeSizeSql(StringInfo buf, Relation rel) } /* - * Construct SELECT statement to acquire the number of rows of a relation. + * Construct SELECT statement to acquire the number of rows and the relkind of + * a relation. * * Note: we just return the remote server's reltuples value, which might * be off a good deal, but it doesn't seem worth working harder. See * comments in postgresAcquireSampleRowsFunc. */ void -deparseAnalyzeTuplesSql(StringInfo buf, Relation rel) +deparseAnalyzeInfoSql(StringInfo buf, Relation rel) { StringInfoData relname; @@ -2383,7 +2384,7 @@ deparseAnalyzeTuplesSql(StringInfo buf, Relation rel) initStringInfo(&relname); deparseRelation(&relname, rel); - appendStringInfoString(buf, "SELECT reltuples FROM pg_catalog.pg_class WHERE oid = "); + appendStringInfoString(buf, "SELECT reltuples, relkind FROM pg_catalog.pg_class WHERE oid = "); deparseStringLiteral(buf, relname.data); appendStringInfoString(buf, "::pg_catalog.regclass"); } diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c index f8461bf18dc..53f890bb483 100644 --- a/contrib/postgres_fdw/postgres_fdw.c +++ b/contrib/postgres_fdw/postgres_fdw.c @@ -4974,11 +4974,14 @@ postgresAnalyzeForeignTable(Relation relation, } /* - * postgresCountTuplesForForeignTable + * postgresGetAnalyzeInfoForForeignTable * Count tuples in foreign table (just get pg_class.reltuples). + * + * can_tablesample determines if the remote relation supports acquiring the + * sample using TABLESAMPLE. */ static double -postgresCountTuplesForForeignTable(Relation relation) +postgresGetAnalyzeInfoForForeignTable(Relation relation, bool *can_tablesample) { ForeignTable *table; UserMapping *user; @@ -4986,6 +4989,10 @@ postgresCountTuplesForForeignTable(Relation relation) StringInfoData sql; PGresult *volatile res = NULL; volatile double reltuples = -1; + volatile char relkind = 0; + + /* assume the remote relation does not support TABLESAMPLE */ + *can_tablesample = false; /* * Get the connection to use. We do the remote access as the table's @@ -4999,7 +5006,7 @@ postgresCountTuplesForForeignTable(Relation relation) * Construct command to get page count for relation. */ initStringInfo(&sql); - deparseAnalyzeTuplesSql(&sql, relation); + deparseAnalyzeInfoSql(&sql, relation); /* In what follows, do not risk leaking any PGresults. */ PG_TRY(); @@ -5008,9 +5015,10 @@ postgresCountTuplesForForeignTable(Relation relation) if (PQresultStatus(res) != PGRES_TUPLES_OK) pgfdw_report_error(ERROR, res, conn, false, sql.data); - if (PQntuples(res) != 1 || PQnfields(res) != 1) + if (PQntuples(res) != 1 || PQnfields(res) != 2) elog(ERROR, "unexpected result from deparseAnalyzeTuplesSql query"); reltuples = strtod(PQgetvalue(res, 0, 0), NULL); + relkind = *(PQgetvalue(res, 0, 1)); } PG_FINALLY(); { @@ -5021,6 +5029,11 @@ postgresCountTuplesForForeignTable(Relation relation) ReleaseConnection(conn); + /* TABLESAMPLE is supported only for regular tables and matviews */ + *can_tablesample = (relkind == RELKIND_RELATION || + relkind == RELKIND_MATVIEW || + relkind == RELKIND_PARTITIONED_TABLE); + return reltuples; } @@ -5148,26 +5161,24 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel, errmsg("remote server does not support TABLESAMPLE feature"))); /* - * For "auto" method, pick the one we believe is best. For servers with - * TABLESAMPLE support we pick BERNOULLI, for old servers we fall-back to - * random() to at least reduce network transfer. - */ - if (method == ANALYZE_SAMPLE_AUTO) - { - if (server_version_num < 95000) - method = ANALYZE_SAMPLE_RANDOM; - else - method = ANALYZE_SAMPLE_BERNOULLI; - } - - /* * If we've decided to do remote sampling, calculate the sampling rate. We * need to get the number of tuples from the remote server, but skip that * network round-trip if not needed. */ if (method != ANALYZE_SAMPLE_OFF) { - reltuples = postgresCountTuplesForForeignTable(relation); + bool can_tablesample; + + reltuples = postgresGetAnalyzeInfoForForeignTable(relation, + &can_tablesample); + + /* + * Make sure we're not choosing TABLESAMPLE when the remote relation does + * not support that. But only do this for "auto" - if the user explicitly + * requested BERNOULLI/SYSTEM, it's better to fail. + */ + if (!can_tablesample && (method == ANALYZE_SAMPLE_AUTO)) + method = ANALYZE_SAMPLE_RANDOM; /* * Remote's reltuples could be 0 or -1 if the table has never been @@ -5213,6 +5224,19 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel, } /* + * For "auto" method, pick the one we believe is best. For servers with + * TABLESAMPLE support we pick BERNOULLI, for old servers we fall-back to + * random() to at least reduce network transfer. + */ + if (method == ANALYZE_SAMPLE_AUTO) + { + if (server_version_num < 95000) + method = ANALYZE_SAMPLE_RANDOM; + else + method = ANALYZE_SAMPLE_BERNOULLI; + } + + /* * Construct cursor that retrieves whole rows from remote. */ cursor_number = GetCursorNumber(conn); diff --git a/contrib/postgres_fdw/postgres_fdw.h b/contrib/postgres_fdw/postgres_fdw.h index 4a633c5357f..02c11523199 100644 --- a/contrib/postgres_fdw/postgres_fdw.h +++ b/contrib/postgres_fdw/postgres_fdw.h @@ -223,7 +223,7 @@ extern void deparseDirectDeleteSql(StringInfo buf, PlannerInfo *root, List *returningList, List **retrieved_attrs); extern void deparseAnalyzeSizeSql(StringInfo buf, Relation rel); -extern void deparseAnalyzeTuplesSql(StringInfo buf, Relation rel); +extern void deparseAnalyzeInfoSql(StringInfo buf, Relation rel); extern void deparseAnalyzeSql(StringInfo buf, Relation rel, PgFdwSamplingMethod sample_method, double sample_frac, |