wangsheng has posted comments on this change. (
http://gerrit.cloudera.org:8080/18023 )
Change subject: IMPALA-7942: Add query hints for cardinalities and selectivities
......................................................................
Patch Set 8:
> Code modification to facilitate above general version of grammar to
> handle predicates and selectivity hints.
>
> Since we put the hint at the class Predicate, it looks like we can
> get the hint for any simple or complex predicate at the right
> place.
>
> [15:00:23 qchen@qifan-10229: Impala.07202021] git diff
> diff --git a/fe/src/main/cup/sql-parser.cup b/fe/src/main/cup/sql-parser.cup
> index bbd1e53d0..bef0b3c1d 100644
> --- a/fe/src/main/cup/sql-parser.cup
> +++ b/fe/src/main/cup/sql-parser.cup
> @@ -307,7 +307,7 @@ terminal
> KW_RANGE, KW_RCFILE, KW_RECOVER, KW_REFERENCES, KW_REFRESH,
> KW_REGEXP, KW_RELY,
> KW_RENAME, KW_REPEATABLE, KW_REPLACE, KW_REPLICATION, KW_RESTRICT,
> KW_RETURNS,
> KW_REVOKE, KW_RIGHT, KW_RLIKE, KW_ROLE, KW_ROLES, KW_ROLLUP,
> KW_ROW, KW_ROWS, KW_SCHEMA,
> - KW_SCHEMAS, KW_SELECT, KW_SEMI, KW_SEQUENCEFILE,
> KW_SERDEPROPERTIES, KW_SERIALIZE_FN,
> + KW_SCHEMAS, KW_SELECT, KW_SELECTIVITY, KW_SEMI,
> KW_SEQUENCEFILE, KW_SERDEPROPERTIES, KW_SERIALIZE_FN,
> KW_SET, KW_SHOW, KW_SMALLINT, KW_SETS, KW_SORT, KW_SPEC, KW_STORED,
> KW_STRAIGHT_JOIN,
> KW_STRING, KW_STRUCT, KW_SYMBOL, KW_SYSTEM_TIME, KW_SYSTEM_VERSION,
> KW_TABLE, KW_TABLES, KW_TABLESAMPLE, KW_TBLPROPERTIES,
> @@ -431,7 +431,7 @@ nonterminal TimeTravelSpec opt_asof;
> nonterminal Subquery subquery;
> nonterminal JoinOperator join_operator;
> nonterminal opt_inner, opt_outer;
> -nonterminal PlanHint plan_hint;
> +nonterminal PlanHint plan_hint, selectivity_hint;
> nonterminal List<PlanHint> plan_hints, opt_plan_hints,
> plan_hint_list;
> nonterminal TypeDef type_def;
> nonterminal Type type;
> @@ -629,6 +629,8 @@ precedence left KW_INTO;
>
> precedence left KW_OVER;
>
> +precedence left COMMENTED_PLAN_HINT_START;
> +
> start with stmt;
>
> stmt ::=
> @@ -3720,6 +3722,15 @@ function_params ::=
> {: RESULT = new FunctionParams(false, true, exprs); :}
> ;
>
> +selectivity_hint ::=
> + COMMENTED_PLAN_HINT_START KW_SELECTIVITY LPAREN
> DECIMAL_LITERAL:value RPAREN
> + COMMENTED_PLAN_HINT_END
> + {:
> + RESULT = new PlanHint("selectivity",
> + new ArrayList(Arrays.asList(value.toString())));
> + :}
> + ;
> +
> predicate ::=
> expr:e KW_IS KW_NULL
> {: RESULT = new IsNullPredicate(e, false); :}
> @@ -3746,6 +3757,8 @@ predicate ::=
> :}
> | expr:e1 KW_LOGICAL_OR expr:e2
> {: RESULT = new CompoundVerticalBarExpr(e1, e2); :}
> + | predicate:p selectivity_hint:h
> + {: RESULT = p; :}
> ;
>
> comparison_predicate ::=
> diff --git a/fe/src/main/jflex/sql-scanner.flex
> b/fe/src/main/jflex/sql-scanner.flex
> index e60676a9c..bc3a91513 100644
> --- a/fe/src/main/jflex/sql-scanner.flex
> +++ b/fe/src/main/jflex/sql-scanner.flex
> @@ -236,6 +236,7 @@ import org.apache.impala.thrift.TReservedWordsVersion;
> keywordMap.put("schemas", SqlParserSymbols.KW_SCHEMAS);
> keywordMap.put("select", SqlParserSymbols.KW_SELECT);
> keywordMap.put("semi", SqlParserSymbols.KW_SEMI);
> + keywordMap.put("selectivity", SqlParserSymbols.KW_SELECTIVITY);
> keywordMap.put("sequencefile", SqlParserSymbols.KW_SEQUENCEFILE);
> keywordMap.put("serdeproperties", SqlParserSymbols.KW_SERDEPROPERTIES);
> keywordMap.put("serialize_fn", SqlParserSymbols.KW_SERIALIZE_FN);
Besides, different predicates have different code logic. For example, we can
use 'p.setSelectivityHint(Double.valueOf(hint.getArgs().get(0)))' for a normal
binary predicate, but for 'NOT LIKE' predicate, Impala will transform to
'CompoundPredicate' with 'NOT' operator, so we set '1 - hint_value' for it's
child, and this is what I did above. Maybe we need consider more of supporting
selectivity hint for compund predicates.
--
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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: I2776b9bbd878b8a21d9c866b400140a454f59e1b
Gerrit-Change-Number: 18023
Gerrit-PatchSet: 8
Gerrit-Owner: wangsheng <[email protected]>
Gerrit-Reviewer: Amogh Margoor <[email protected]>
Gerrit-Reviewer: Fucun Chu <[email protected]>
Gerrit-Reviewer: Impala Public Jenkins <[email protected]>
Gerrit-Reviewer: Qifan Chen <[email protected]>
Gerrit-Reviewer: Quanlong Huang <[email protected]>
Gerrit-Reviewer: Zoltan Borok-Nagy <[email protected]>
Gerrit-Reviewer: wangsheng <[email protected]>
Gerrit-Comment-Date: Sat, 19 Mar 2022 10:37:38 +0000
Gerrit-HasComments: No
