Github user DaveBirdsall commented on a diff in the pull request:
https://github.com/apache/incubator-trafodion/pull/513#discussion_r65590770
--- Diff: core/conn/odbc/src/odbc/nsksrvrcore/srvrothers.cpp ---
@@ -4811,6 +4811,64 @@ odbc_SQLSvc_GetSQLCatalogs_sme_(
break;
+ case SQL_API_SQLSTATISTICS:
+ if (!checkIfWildCard(catalogNm, catalogNmNoEsc) && !metadataId)
+ {
+ exception_->exception_nr =
odbc_SQLSvc_GetSQLCatalogs_ParamError_exn_;
+ exception_->u.ParamError.ParamDesc =
SQLSVC_EXCEPTION_WILDCARD_NOT_SUPPORTED;
+ }
+ if (tableNm[0] != '$' && tableNm[0] != '\\')
+ {
+ if (strcmp(catalogNm, "") == 0)
+ strcpy(tableName1, SEABASE_MD_CATALOG);
+ else
+ strcpy(tableName1, catalogNm);
+ }
+
+ tableParam[0] = tableName1;
+ convertWildcard(metadataId, TRUE, schemaNm, expSchemaNm);
+ convertWildcardNoEsc(metadataId, TRUE, schemaNm,
schemaNmNoEsc);
+ convertWildcard(metadataId, TRUE, tableNm, expTableNm);
+ convertWildcardNoEsc(metadataId, TRUE, tableNmNoEsc,
tableNmNoEsc);
+ inputParam[0] = schemaNmNoEsc;
+ inputParam[1] = expSchemaNm;
+ inputParam[2] = tableNmNoEsc;
+ inputParam[3] = expTableNm;
+
+ snprintf(CatalogQuery, sizeof(CatalogQuery),
+ "select "
+ "cast('%s' as varchar(128)) TABLE_CAT, "
+ "cast(trim(ob.SCHEMA_NAME) as varchar(128))
TABLE_SCHEM, "
+ "cast(trim(ob.OBJECT_NAME) as varchar(128))
TABLE_NAME, "
+ "cast(0 as smallint) NON_UNIQUE, " // not support
+ "cast('' as varchar(128)) INDEX_QUALIFIER, " // not
support
+ "cast('' as varchar(128)) INDEX_NAME, "
+ "cast(0 as smallint) TYPE, " // not support
+ "cast((case when (trim(co.COLUMN_CLASS) <> 'S') then
co.column_number+1 else "
+ "co.column_number end) as smallint)
ORDINAL_POSITION, "
+ "cast(trim(co.COLUMN_NAME) as varchar(128))
COLUMN_NAME, "
+ "cast('' as char(1)) ASC_OR_DES, "
+ "cast(sb.rowcount as integer) CARDINALITY, "
+ "cast(0 as integer) PAGES, " // not support
+ "cast('' as varchar(128)) FILTER_CONDITION " // not
support
+ "from "
+ "TRAFODION.\"_MD_\".OBJECTS ob, "
+ "TRAFODION.\"_MD_\".COLUMNS co, "
+ "TRAFODION.%s.sb_histograms sb "
+ "where "
+ "ob.OBJECT_UID = co.OBJECT_UID "
+ "and co.COLUMN_NUMBER = sb.COLUMN_NUMBER "
--- End diff --
Unfortunately, I don't know of a document either. I've learned the format
of the data in the Histograms table by reverse-engineering it, along with a
little bit of code reading. Here's what I know: For a multi-column histogram,
there will be n rows in the SB_HISTOGRAMS table, where n is the number of
columns in the histogram. One way to see this is to create a table with a
primary key, put some rows into it (100 rows, let's say),then do UPDATE
STATISTICS ON EVERY COLUMN. After that, do SHOWSTATS ON EVERY COLUMN. That will
show you the table_uid for that table. Then do "select histogram_id, count(*)
from sb_histograms where table_uid = <the value from SHOWSTATS> group by
histogram_id". You'll notice some histogram_id's with counts of one. Those are
the single column histograms. You'll also notice a few with counts greater than
one. These are the multi-column histograms. If you then look at the rows for
that particular histogram_id, you'll see there is a row for each column in the
histogram. It is a denormalized representation.
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