From cc3f4b5b9e438c7d27d7f5fe55e0bc7bc0e3fc0d Mon Sep 17 00:00:00 2001
From: alrocar <alrocar@tinybird.co>
Date: Wed, 2 Oct 2024 11:05:18 +0200
Subject: [PATCH] support extract

---
 src/custom_types.c             | 11 +++++++++
 src/deparse.c                  | 44 ++++++++++++++++++++++++++++++++++
 src/include/clickhousedb_fdw.h |  1 +
 3 files changed, 56 insertions(+)

diff --git a/src/custom_types.c b/src/custom_types.c
index 6585d49..fdbf3af 100644
--- a/src/custom_types.c
+++ b/src/custom_types.c
@@ -27,6 +27,8 @@
 #define F_TIMESTAMP_ZONE 2069
 #define F_TIMESTAMPTZ_ZONE 1159
 #define F_TIMESTAMPTZ_PART 1171
+#define F_TIMESTAMP_EXTRACT 6202
+#define F_TIMESTAMPTZ_EXTRACT 6203
 #define F_TO_TIMESTAMP 1778
 #define F_ARRAY_POSITION 3277
 #define F_STRPOS 868
@@ -99,6 +101,8 @@ CustomObjectDef *chfdw_check_for_custom_function(Oid funcid)
 		{
 			case F_TIMESTAMP_TRUNC:
 			case F_TIMESTAMPTZ_TRUNC:
+			case F_TIMESTAMP_EXTRACT:
+			case F_TIMESTAMPTZ_EXTRACT:
 			case F_TIMESTAMP_ZONE:
 			case F_TIMESTAMPTZ_ZONE:
 			case F_TIMESTAMP_PART:
@@ -145,6 +149,13 @@ CustomObjectDef *chfdw_check_for_custom_function(Oid funcid)
 				entry->custom_name[0] = '\1';
 				break;
 			}
+			case F_TIMESTAMPTZ_EXTRACT:
+			case F_TIMESTAMP_EXTRACT:
+			{
+				entry->cf_type = CF_EXTRACT;
+				entry->custom_name[0] = '\1';
+				break;
+			}
 			case F_TIMESTAMP_ZONE:
 			case F_TIMESTAMPTZ_ZONE:
 			{
diff --git a/src/deparse.c b/src/deparse.c
index 72ca941..e121099 100644
--- a/src/deparse.c
+++ b/src/deparse.c
@@ -2468,6 +2468,50 @@ deparseFuncExpr(FuncExpr *node, deparse_expr_cxt *context)
 		appendStringInfoChar(buf, ')');
 		return;
 	}
+	else if (cdef && cdef->cf_type == CF_EXTRACT)
+	{
+		if (list_length(node->args) != 2)
+        	elog(ERROR, "extract requires exactly two arguments");
+
+		Const *arg = (Const *) linitial(node->args);
+		char *parttype = TextDatumGetCString(arg->constvalue);
+		CSTRING_TOLOWER(parttype);
+
+		Expr *source_expr = (Expr *) lsecond(node->args);
+
+		if (strcmp(parttype, "day") == 0)
+			appendStringInfoString(buf, "toDayOfMonth");
+		else if (strcmp(parttype, "doy") == 0)
+			appendStringInfoString(buf, "toDayOfYear");
+		else if (strcmp(parttype, "dow") == 0)
+			appendStringInfoString(buf, "toDayOfWeek");
+		else if (strcmp(parttype, "year") == 0)
+			appendStringInfoString(buf, "toYear");
+		else if (strcmp(parttype, "month") == 0)
+			appendStringInfoString(buf, "toMonth");
+		else if (strcmp(parttype, "hour") == 0)
+			appendStringInfoString(buf, "toHour");
+		else if (strcmp(parttype, "minute") == 0)
+			appendStringInfoString(buf, "toMinute");
+		else if (strcmp(parttype, "second") == 0)
+			appendStringInfoString(buf, "toSecond");
+		else if (strcmp(parttype, "quarter") == 0)
+			appendStringInfoString(buf, "toQuarter");
+		else if (strcmp(parttype, "isoyear") == 0)
+			appendStringInfoString(buf, "toISOYear");
+		else if (strcmp(parttype, "week") == 0)
+			appendStringInfoString(buf, "toISOWeek");
+		else if (strcmp(parttype, "epoch") == 0)
+			appendStringInfoString(buf, "toUnixTimestamp");
+		else
+			elog(ERROR, "extract cannot be exported for: %s", parttype);
+
+		pfree(parttype);
+		appendStringInfoChar(buf, '(');
+		deparseExpr(source_expr, context);
+		appendStringInfoChar(buf, ')');
+		return;
+	}
 	else if (cdef && cdef->cf_type == CF_ISTORE_SEED)
 	{
 		if (!context->func)
diff --git a/src/include/clickhousedb_fdw.h b/src/include/clickhousedb_fdw.h
index 43e218e..91f9eae 100644
--- a/src/include/clickhousedb_fdw.h
+++ b/src/include/clickhousedb_fdw.h
@@ -270,6 +270,7 @@ typedef enum {
 	CF_AJTIME_TO_TIMESTAMP,	/* ajtime to timestamp */
 	CF_DATE_TRUNC,		/* date_trunc function */
 	CF_DATE_PART,		/* date_part function */
+	CF_EXTRACT,		/* extract function */
 	CF_TIMESTAMPTZ_PL_INTERVAL,	/* timestamptz + interval */
 	CF_TIMEZONE,		/* timezone */
 	CF_TO_TIMESTAMP,