MaxGekk commented on code in PR #56409: URL: https://github.com/apache/spark/pull/56409#discussion_r3402459633
########## sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/ResolveTimestampNanosCast.scala: ########## @@ -0,0 +1,126 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.spark.sql.catalyst.analysis + +import org.apache.spark.sql.catalyst.expressions.Cast +import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan +import org.apache.spark.sql.catalyst.rules.Rule +import org.apache.spark.sql.catalyst.trees.TreePattern.CAST +import org.apache.spark.sql.types.{ArrayType, DataType, DateType, MapType, StructType, TimestampLTZNanosType, TimestampNTZNanosType, TimestampNTZType, TimestampType} + +/** + * Rewrites casts between [[DateType]] and the nanosecond-precision timestamp types + * ([[TimestampLTZNanosType]] / [[TimestampNTZNanosType]]) into a two-step cast that goes through + * the corresponding microsecond-precision timestamp type: + * + * - `nanos(p) -> DATE` ==> `nanos(p) -> micros -> DATE` + * - `DATE -> nanos(p)` ==> `DATE -> micros -> nanos(p)` + * + * where the microsecond counterpart is `TIMESTAMP` for `*_LTZ` and `TIMESTAMP_NTZ` for `*_NTZ`. + * Both component casts already exist (`nanos(p) <-> micros` and `micros <-> DATE`), so no dedicated + * `DATE <-> nanos` conversion is needed in [[Cast]] and the semantics match the microsecond + * `DATE <-> TIMESTAMP` casts: the LTZ directions are resolved in the session time zone and the NTZ + * directions on the UTC wall-clock grid; sub-microsecond digits and the time-of-day are dropped + * when narrowing to `DATE`. + * + * The same rewrite applies when the `DATE <-> nanos` pair is nested inside complex types + * ([[ArrayType]] / [[MapType]] / [[StructType]]) at any depth, e.g. + * `ARRAY<nanos(p)> -> ARRAY<DATE>` becomes `ARRAY<nanos(p)> -> ARRAY<micros> -> ARRAY<DATE>`. The + * intermediate type mirrors the structure (and nullability) of the target type, with every + * `DATE <-> nanos` leaf swapped for the corresponding microsecond-precision timestamp type, so that + * both component casts pass `Cast.canCast`. + * + * `Cast.canCast` intentionally does not allow `DATE <-> nanos` directly (it recurses into complex + * types, so nested pairs are rejected too), so such a cast stays unresolved until this rule + * rewrites it into the resolvable nested form. The new casts inherit the original `timeZoneId` and + * `evalMode`; the only zone-sensitive part (the `micros <-> DATE` cast) gets its session time zone + * from [[ResolveTimeZone]] within the same fixed-point batch. + * + * The per-cast rewrite is exposed via [[rewriteDateNanosCast]] so that the single-pass resolver + * (see `TimezoneAwareExpressionResolver`) can apply the same transformation and produce an + * identical plan; otherwise single-pass resolution would fail the cast's input type check while + * fixed-point succeeds. + */ +object ResolveTimestampNanosCast extends Rule[LogicalPlan] { Review Comment: @cloud-fan ok, could you review another approach https://github.com/apache/spark/pull/56375. I migrated a few tests from this PR. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
