From 261dbf8f8de42927173fc0b59cdf47ed0f3f4ff7 Mon Sep 17 00:00:00 2001
From: Amit Aggarwal <amit@datairis.io>
Date: Thu, 2 Jan 2025 17:13:50 -0800
Subject: [PATCH] For nested fields we were using lateral flatten. The issue
 with it is that if the nested field is used in a join, snowflake complains
 that lateral flatten can't be on left side of join
 (https://stackoverflow.com/questions/63397022/snowflake-lateral-cannot-be-on-the-left-side-of-join)

fix is to always convert lateral flatten to a left join

Also simplify the array[scalar] vs array[record] treatment. earlier, at the
unnesting step we were creating a object for array[scalar] case to make it
consistent with the array[record] case. Now at the reference time, based on
the case, use the right expression
- array[record] : parent.value:sql_field
- array[scalar] : parent.value

Signed-off-by: Amit Aggarwal <amit@datairis.io>
---
 packages/malloy/src/dialect/snowflake/snowflake.ts | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/packages/malloy/src/dialect/snowflake/snowflake.ts b/packages/malloy/src/dialect/snowflake/snowflake.ts
index c0328c36e..a49a9653a 100644
--- a/packages/malloy/src/dialect/snowflake/snowflake.ts
+++ b/packages/malloy/src/dialect/snowflake/snowflake.ts
@@ -204,7 +204,7 @@ export class SnowflakeDialect extends Dialect {
   ): string {
     const as = this.sqlMaybeQuoteIdentifier(alias);
     if (isArray) {
-      return `,LATERAL FLATTEN(INPUT => ${source}) AS ${alias}_1, LATERAL (SELECT ${alias}_1.INDEX, object_construct('value', ${alias}_1.value) as value ) as ${as}`;
+      return `LEFT JOIN lateral flatten(input =>  ${source}) as ${as}`;
     } else {
       // have to have a non empty row or it treats it like an inner join :barf-emoji:
       return `LEFT JOIN LATERAL FLATTEN(INPUT => ifnull(${source},[1])) AS ${as}`;
@@ -266,7 +266,16 @@ export class SnowflakeDialect extends Dialect {
       parentType === 'array[scalar]' ||
       parentType === 'array[record]'
     ) {
-      const arrayRef = `"${parentAlias}".value:${sqlName}`;
+      // Case 1: this is an array of scalar. We can reference the field
+      // simply as parent.value. in fact the sqlName will be value always
+      // because there is nothing else to reference.
+      // Case 2: this is an array of records. In this case, parent.value
+      // gives the record and then parent.value:sql_name gives the
+      // right field in the record.
+      let arrayRef = `"${parentAlias}".value:${sqlName}`;
+      if (parentType === 'array[scalar]') {
+        arrayRef = `"${parentAlias}".value`;
+      }
       switch (childType) {
         case 'record':
         case 'array':