Update

I wrote the original post yesterday but due to delays I didn't publish it until today.  I've played around with this and came up with an improvement.

 

Onward

Seeing that Tableau translated TRUE to 1=1, which is further complicated by Tableau putting logic around it via the CASE statement, why bother having a CASE statement slow things down when I'm only interested in one condition of the output of the CASE statement?  The only output I care about from the CASE statement is 1 so I changed the left side of the Join Condition from TRUE to just 1:

 

 

When I looked at the SQL using the Convert to Custom SQL that second CASE statement was gone!

...

"ITEM_LOC_VENDOR_DIM_V"."CURR_TS" AS "CURR_TS",

(CASE WHEN ("ITEM_LOC_VENDOR_DIM_V"."PRIM_ALT_VNDR_CD" = 'P') THEN 1 WHEN NOT ("ITEM_LOC_VENDOR_DIM_V"."PRIM_ALT_VNDR_CD" = 'P') THEN 0 ELSE NULL END) AS "$temp0"

  FROM "CUSTOMS"."ITEM_LOC_VENDOR_DIM_V" "ITEM_LOC_VENDOR_DIM_V"

  ) "t0" ON

  (

   ("RVC_TOOL_NAFTA_V"."CO_CD" = "t0"."CO_CD")

   AND ("RVC_TOOL_NAFTA_V"."ORG_CD" = "t0"."ORG_CD")

   AND ("RVC_TOOL_NAFTA_V"."PLNT_CD" = "t0"."PLNT_CD")

   AND ("RVC_TOOL_NAFTA_V"."SUPLR_CD" = "t0"."SUPLR_CD")

   AND ("RVC_TOOL_NAFTA_V"."CHILD_ITEM_NO" = "t0"."ITEM_NO")

   AND (1 = "t0"."$temp0")

   )

  LEFT JOIN "CUSTOMS"."PURCHASING_BUYER" "PURCHASING_BUYER" ON

( ("t0"."PPF_BYR_CD" = "PURCHASING_BUYER"."BYR_CD") AND ("t0"."SUPLR_CD" = "PURCHASING_BUYER"."SUPLR_CD") )

 

See that, I went from a time-consuming CASE statement to a simpler condition of (1 = "t0"."$temp0").  I canceled the custom SQL and ran the extract.  It ran almost 30 seconds faster!