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db_include/access/toast_helper.h

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+/*-------------------------------------------------------------------------
+ *
+ * toast_helper.h
+ *	  Helper functions for table AMs implementing compressed or
+ *    out-of-line storage of varlena attributes.
+ *
+ * Copyright (c) 2000-2021, PostgreSQL Global Development Group
+ *
+ * src/include/access/toast_helper.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef TOAST_HELPER_H
+#define TOAST_HELPER_H
+
+#include "utils/rel.h"
+
+/*
+ * Information about one column of a tuple being toasted.
+ *
+ * NOTE: toast_action[i] can have these values:
+ *		' '						default handling
+ *		TYPSTORAGE_PLAIN		already processed --- don't touch it
+ *		TYPSTORAGE_EXTENDED		incompressible, but OK to move off
+ *
+ * NOTE: toast_attr[i].tai_size is only made valid for varlena attributes with
+ * toast_action[i] different from TYPSTORAGE_PLAIN.
+ */
+typedef struct
+{
+	struct varlena *tai_oldexternal;
+	int32		tai_size;
+	uint8		tai_colflags;
+	char		tai_compression;
+} ToastAttrInfo;
+
+/*
+ * Information about one tuple being toasted.
+ */
+typedef struct
+{
+	/*
+	 * Before calling toast_tuple_init, the caller must initialize the
+	 * following fields.  Each array must have a length equal to
+	 * ttc_rel->rd_att->natts.  The tts_oldvalues and tts_oldisnull fields
+	 * should be NULL in the case of an insert.
+	 */
+	Relation	ttc_rel;		/* the relation that contains the tuple */
+	Datum	   *ttc_values;		/* values from the tuple columns */
+	bool	   *ttc_isnull;		/* null flags for the tuple columns */
+	Datum	   *ttc_oldvalues;	/* values from previous tuple */
+	bool	   *ttc_oldisnull;	/* null flags from previous tuple */
+
+	/*
+	 * Before calling toast_tuple_init, the caller should set tts_attr to
+	 * point to an array of ToastAttrInfo structures of a length equal to
+	 * tts_rel->rd_att->natts.  The contents of the array need not be
+	 * initialized.  ttc_flags also does not need to be initialized.
+	 */
+	uint8		ttc_flags;
+	ToastAttrInfo *ttc_attr;
+} ToastTupleContext;
+
+/*
+ * Flags indicating the overall state of a TOAST operation.
+ *
+ * TOAST_NEEDS_DELETE_OLD indicates that one or more old TOAST datums need
+ * to be deleted.
+ *
+ * TOAST_NEEDS_FREE indicates that one or more TOAST values need to be freed.
+ *
+ * TOAST_HAS_NULLS indicates that nulls were found in the tuple being toasted.
+ *
+ * TOAST_NEEDS_CHANGE indicates that a new tuple needs to built; in other
+ * words, the toaster did something.
+ */
+#define TOAST_NEEDS_DELETE_OLD				0x0001
+#define TOAST_NEEDS_FREE					0x0002
+#define TOAST_HAS_NULLS						0x0004
+#define TOAST_NEEDS_CHANGE					0x0008
+
+/*
+ * Flags indicating the status of a TOAST operation with respect to a
+ * particular column.
+ *
+ * TOASTCOL_NEEDS_DELETE_OLD indicates that the old TOAST datums for this
+ * column need to be deleted.
+ *
+ * TOASTCOL_NEEDS_FREE indicates that the value for this column needs to
+ * be freed.
+ *
+ * TOASTCOL_IGNORE indicates that the toaster should not further process
+ * this column.
+ *
+ * TOASTCOL_INCOMPRESSIBLE indicates that this column has been found to
+ * be incompressible, but could be moved out-of-line.
+ */
+#define TOASTCOL_NEEDS_DELETE_OLD			TOAST_NEEDS_DELETE_OLD
+#define TOASTCOL_NEEDS_FREE					TOAST_NEEDS_FREE
+#define TOASTCOL_IGNORE						0x0010
+#define TOASTCOL_INCOMPRESSIBLE				0x0020
+
+extern void toast_tuple_init(ToastTupleContext *ttc);
+extern int	toast_tuple_find_biggest_attribute(ToastTupleContext *ttc,
+											   bool for_compression,
+											   bool check_main);
+extern void toast_tuple_try_compression(ToastTupleContext *ttc, int attribute);
+extern void toast_tuple_externalize(ToastTupleContext *ttc, int attribute,
+									int options);
+extern void toast_tuple_cleanup(ToastTupleContext *ttc);
+
+extern void toast_delete_external(Relation rel, Datum *values, bool *isnull,
+								  bool is_speculative);
+
+#endif